nist-janaf thermochemical tables

NIST-JANAF Thermochemical Tables. I. Ten Organic MoleculesRelated to Atmospheric Chemistry

Olga Dorofeeva a…

Physical and Chemical Properties Division, Chemical Science and Technology Laboratory,National Institute of Standards and Technology, Gaithersburg, Maryland 20899

Vladimir P. NovikovDepartment of Chemistry, Moscow State University, Moscow 119899, Russia

David B. Neumann b…

Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, Baltimore, Maryland 21250

~Received 6 September 2000; accepted 16 January 2001!

The structural, spectroscopic, and thermodynamic properties of 10 gas phase organicmolecules related to atmospheric chemistry, including three peroxides and four carboxy-lic acids, are reviewed. The calculation of the thermochemical tables involved the criticalevaluation of new spectroscopic data, enthalpy of formation determinations, and the useof recent internal rotation data. Since insufficient information to characterize all 10 mol-ecules exists, estimation schemes were used to provide the missing experimental andtheoretical data. ©2001 by the U.S. Secretary of Commerce on behalf of the UnitedStates. All rights reserved.

Key words: critical evaluation; enthalpy of formation; group additivity method; heat capacity; internalrotation; molecular structure; normal coordinates; spectroscopic properties; thermodynamic properties;transferable force fields.

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Contents

1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472. Bromoacetic Acid, CH2Br—COOH. . . . . . . . . . . . 478

2.1. Enthalpy of Formation. . . . . . . . . . . . . . . . . . . 4782.2. Heat Capacity and Entropy. . . . . . . . . . . . . . . . 4792.3. References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 480

3. Chloroacetic Acid, CH2Cl—COOH. . . . . . . . . . . . 4813.1. Enthalpy of Formation. . . . . . . . . . . . . . . . . . . 4823.2. Heat Capacity and Entropy. . . . . . . . . . . . . . . . 4833.3. References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484

4. Oxopropanedinitrile, NC—CO—CN. . . . . . . . . . . . 4854.1. Enthaply of Formation. . . . . . . . . . . . . . . . . . . 4854.2. Heat Capacity and Entropy. . . . . . . . . . . . . . . . 4854.3. References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486

5. Glycolic Acid, HO—CH2—COOH.. . . . . . . . . . . . 4875.1. Enthalpy of Formation. . . . . . . . . . . . . . . . . . . 4885.2. Heat Capacity and Entropy. . . . . . . . . . . . . . . . 4895.3. References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490

6. Glyoxal, OvCH—CHvO. . . . . . . . . . . . . . . . . . . 492

a!Guest Researcher, currently at the Glushko Thermocenter of the RuAcademy of Sciences, IVTAN Association of the RAS, Izhorskaya13/19, Moscow 127412, Russia; Electronic mail: [email protected].

b!Visiting Professor, currently at TPC Data Associates, Box 190, Washton Grove, MD, 20880-0190; Electronic mail: [email protected].© 2001 by the U.S. Secretary of Commerce on behalf of the United StaAll rights reserved.

0047-2689Õ2001Õ30„2…Õ475Õ39Õ$35.00 475

Downloaded 02 Jul 2012 to 129.6.105.191. Redistribution subject to AIP lic

6.1. Enthalpy of Formation. . . . . . . . . . . . . . . . . . . 4936.2. Heat Capacity and Entropy. . . . . . . . . . . . . . . . 4936.3. References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495

7. Cyanooxomethyl Radical, OC˙ CN. . . . . . . . . . . . . . 4967.1. Enthalpy of Formation. . . . . . . . . . . . . . . . . . . 4967.2. Heat Capacity and Entropy. . . . . . . . . . . . . . . . 4967.3. References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497

8. Oxalic Acid, HO—CO—CO—OH. . . . . . . . . . . . . 4988.1. Enthalpy of Formation. . . . . . . . . . . . . . . . . . . 4988.2. Heat Capacity and Entropy. . . . . . . . . . . . . . . . 4988.3. References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 499

9. Methyl Hydroperoxide, CH3—O—O—H. . . . . . . . 5009.1. Enthalpy of Formation. . . . . . . . . . . . . . . . . . . 5019.2. Heat Capacity and Entropy. . . . . . . . . . . . . . . . 5029.3. References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 502

10. Dimethyl Peroxide, CH3—O—O—CH3. . . . . . . . . 50410.1. Enthalpy of Formation. . . . . . . . . . . . . . . . . . 50410.2. Heat Capacity and Entropy. . . . . . . . . . . . . . 50510.3. References. . . . . . . . . . . . . . . . . . . . . . . . . . . . 505

11. Diacetyl Peroxide,CH3—CO—O—O—CO—CH3. . . . . . . . . . . . . . . . 50711.1. Enthalpy of Formation. . . . . . . . . . . . . . . . . . 50811.2. Heat Capacity and Entropy. . . . . . . . . . . . . . 50811.3. References. . . . . . . . . . . . . . . . . . . . . . . . . . . . 509

12. Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51013. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . 51014. Extended Bibliographies. . . . . . . . . . . . . . . . . . . . . 510

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J. Phys. Chem. Ref. Data, Vol. 30, No. 2, 2001

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476476 DOROFEEVA, NOVIKOV, AND NEUMANN

14.1. Extended Bibliography for BromoaceticAcid, C2H3BrO2. . . . . . . . . . . . . . . . . . . . . . . 510

14.2. Extended Bibliography for ChloroaceticAcid, C2H3ClO2. . . . . . . . . . . . . . . . . . . . . . . 510

14.3. Extended Bibliography forOxopropanedinitrile, C3N2O. . . . . . . . . . . . . . 511

14.4. Extended Bibliography for Glycolic Acid,C2H4O3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511

14.5. Extended Bibliography for Glyoxal,C2H2O2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511

14.6. Extended Bibliography forCyanooxomethyl Radical, NC2O. . . . . . . . . . 512

14.7. Extended Bibliography for Oxalic Acid,C2H2O4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513

14.8. Extended Bibliography for MethylHydroperoxide, CH4O2. . . . . . . . . . . . . . . . . . 513

14.9. Extended Bibliography for DimethylPeroxide, C2H6O2. . . . . . . . . . . . . . . . . . . . . . 513

14.10. Extended Bibliography for DiacetylPeroxide, C4H6O4. . . . . . . . . . . . . . . . . . . . . 513

List of Tables1. Ideal gas thermodynamic properties of

bromoacetic acid C2H3BrO2~g! at the standardstate pressure,p°50.1 MPa~Tr5298.15 K). . . . . 481

2. Ideal gas thermodynamic properties ofchloroacetic acid C2H3ClO2~g! at the standardstate pressure,p°50.1 MPa~Tr5298.15 K!. . . . . . 483

3. Ideal gas thermodynamic properties ofoxopropanedinitrile C3N2O~g! at the standard statepressure,p°50.1 MPa~Tr5298.15 K). .. . . . . . . . 487

4. Ideal gas thermodynamic properties of glycolicacid C2H4O3~g! at the standard state pressure,p°50.1 MPa~Tr5298.15 K). . . . . . . . . . . . . . . . . . 491

5. Ideal gas thermodynamic properties of glyoxalC2H2O2~g! at the standard state pressure,p°50.1 MPa~Tr5298.15 K). . . . . . . . . . . . . . . . . . . . 494

6. Ideal gas thermodynamic properties of thecyanooxomethyl radical C2NO~g! at the standardstate pressure,p°50.1 MPa (Tr5298.15 K). . . . . 497

7. Ideal gas thermodynamic properties of oxalicacid C2H2O4~g! at the standard state pressure,p°50.1 MPa (Tr5298.15 K). . . . . . . . . . . . . . . . . 500

8. Ideal gas thermodynamic properties of methylhydroperoxide CH4O2~g! at the standard statepressure,p°50.1 MPa (Tr5298.15 K).. . . . . . . . 503

9. Ideal gas thermodynamic properties of dimethylperoxide C2H6O2~g! at the standard statepressure,p°50.1 MPa (Tr5298.15 K).. . . . . . . . 506

10. Ideal gas thermodynamic properties of diacetylperoxide, C4H6O4~g! at the standard statepressure,p°50.1 MPa (Tr5298.15 K).. . . . . . . . 509

11. Summary of the thermodynamic properties at298.15 K and the standard state pressure,p°50.1 MPa. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51



1. Introduction

A large number of biogenic and industrial polutant specplay a direct or indirect role in tropospheric smog chemistModeling of the kinetics of tropospheric chemical reactiprocesses often requires thermodynamic data. In the folling, evaluated thermodynamic data for a few smaller orgaspecies including some peroxides relevant to smog chemand atmospheric chemistry in general are presented.

The ideal gas thermodynamic properties of the polyatommolecules were calculated by standard statistical mechanmethods in which a rigid-rotor harmonic-oscillator modemodified where appropriate for internal rotations, wassumed for each compound. The statistical formulas for thmodynamic functions are discussed in several textbooksview articles, and reference books.1–6 Molecular andspectroscopic constants needed for the calculations werelected from the literature. In a few cases missing data westimated by analogy to related compounds. For some mecules, the fundamental frequencies were estimated bymal coordinate calculations using force constants transfefrom related molecules and the program NCA writtenNovikov and Malyshev.7

To evaluate the internal rotational contributions to tthermodynamic functions, the internal rotational partitifunction was formed by the summation of internal rotationenergy levels for each rotor. These energy levels weretained by the diagonalization of the one dimensional Hamtonian using a potential function of the form

V~w!51

2 (n

Vn~12cosnw!, ~1!

wherew is the internal rotational angle. The method of geerating the internal rotation energy levels has been descrby Lewis et al.8,9 The constant required to generate theternal rotational energy levels for each rotor is the interrotational constant~F ! or reduced moment of inertia of throtating group (I r). Where available, theVn terms and inter-nal rotational constant were taken from spectroscopic datthe F value was unavailable, it was calculated from theduced moment of inertia with the relationship

F5h/8p2cIr . ~2!

The value ofI r was calculated using molecular structurparameters with a computer program based on a methocalculating the reduced moments of inertia developedPitzer and Gwinn.10,11

A molecular model of an equilibrium mixture oftransandcis isomers was employed for calculating the thermodynamfunctions of glyoxal.4,12,13This method uses the enthalpy diference between the two conformers to calculate the equrium mole fraction of each species. From these datathermodynamic functions of two conformers, values of thmodynamic functions were calculated, allowing for the ming of two conformers.

The sources of uncertainties in the calculated thermonamic functions arise from uncertainties in the molecu


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477477NIST-JANAF THERMOCHEMICAL TABLES

constants used in the calculations as well as deviations fthe rigid-rotor harmonic-oscillator model. In this work thuncertainties in the thermodynamic functions were estimaby the procedure developed by Gurvichet al.6 This approachpredicts the uncertainties in the thermodynamic functioS°(T) andCp°(T) for simple molecules such as C3N2O rea-sonably well. For molecules with one or more internal rotions, the additional uncertainties due to deviations fromrigid-rotor harmonic-oscillator model are difficult to asseThe largest uncertainty probably arises from the anharmoity of the asymmetric torsion. This will have little effect aroom temperature but may be significant at the higher teperatures. The total estimated uncertainties in the thermonamic functionsS°(T) and Cp°(T) in the range between298.15 and 2000 K are given in the discussions for emolecule.

Based on the selected values of the molecular constathe ideal gas thermodynamic functions, heat capacCp°(T), entropy, S°(T), enthalpy @H°(T)2H°(298.15 K)#, and the Gibbs energy functio$2@G°(T)2H°(298.15 K)#/T%, have been calculated foselected temperatures up to 2000 K at the standard statesure,p°50.1 MPa.~In the tables that follow in a few caseexcited electronic states have been factored into the calctions; the energy of an electronic state relative to the groelectronic state is given as«G ; the degeneracy of electronistates are referred to in these tables as the ‘‘quanweight,’’ gG.) The enthalpy of formation value@D fH°(298.15 K)# were selected by analyzing experimenstudies which may result in the enthalpies of formationtermination. In the absence of experimental data,D fH°(298.15 K) values were estimated by approximamethods accepted as standard for organic moleculesradicals.14,15

The calculated values of the enthalpy difference,@H°(T)2H°(298.15 K)#, and entropy,S°(T), of the ideal gas were


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combined with values of the enthalpies and entropies ofelements in their reference states to derive values of enthof formation (D fH°), Gibbs energy of formation (D fG°),and the logarithm of the equilibrium constant of formatio(logKf°) of the substances as a function of temperature othe range of 0–2000 K.

Values used here of@H°(T)-H°(298.15 K)# and S°(T)for the elements in their reference states@H2~g!, C~cr, graph-ite!, O2~g!, N2~g!, F2~g!, Cl2~g!, and Br2~cr,liq,T,332.503 K) and Br2~g,T.332.503 K] are those given inthe JANAF Thermochemical Tables.5

References

1K. S. Pitzer,Quantum Chemistry~Prentice–Hall, Englewood Cliffs, NJ1953!.

2J. G. Aston and J. J. Fritz,Thermodynamics and Statistical Thermodynaics ~Wiley, New York, 1959!.

3G. N. Lewis, M. Randall, K. S. Pitzer, and L. Brewer,Thermodynamics,2nd ed.~McGraw–Hill, New York, 1961!.

4S. G. Frankiss and J. H. S. Green,Chemical Thermodynamics~TheChemical Society, London, 1973!, Vol. 1, Chap. 8, pp. 268–316.

5M. W. Chase, Jr., C. A. Davies, J. R. Downey, Jr., D. J. Frurip, R.McDonald, and A. N. Syverud,JANAF Thermochemical Tables, 3rd ed.@J. Phys. Chem. Ref. Data14, Suppl. 1~1985!#.

6L. V. Gurvich, I. V. Veyts, and C. B. Alcock,Thermodynamic Propertiesof Individual Substances, 4th ed.~Hemisphere, New York, 1989!, Vol. 1,Part 1.

7V. P. Novikov and A. I. Malyshev, Zh. Prikl. Spektrosk.33, 545 ~1980!.8J. D. Lewis, T. B. Malloy, Jr., T. H. Chao, and J. Laane, J. Mol. Struct.12,427 ~1972!.

9J. D. Lewis and J. Laane, J. Mol. Spectrosc.65, 147 ~1977!.10K. S. Pitzer and W. D. Gwinn, J. Chem. Phys.10, 428 ~1942!.11K. S. Pitzer, J. Chem. Phys.14, 239 ~1946!.12K. S. Pitzer, J. Chem. Phys.5, 473 ~1937!.13J. G. Aston and G. Szasz, J. Chem. Phys.14, 67 ~1946!.14N. Cohen and S. W. Benson, Chem. Rev.93, 2419~1993!.15D. R. Stull, E. G. Westrum, Jr., and G. C. Sinke,The Chemical Thermo-

dynamics of Organic Compounds~Krieger, Malabar, FL, 1987!.




2. Bromoacetic Acid, CH 2Br—COOH

Bromoacetic acid (C2H3BrO2) Ideal gas Mr5138.9485D fH°(0 K)52364.663.1 kJ mol21

S°(298.15 K)5337.065.0 J K21 mol21 D fH°(298.15 K)52383.563.1 kJ mol21

Molecular constantsPoint group:Cs Symmetry number:s51Ground electronic state:X 1A Energy:eX50 cm21 Quantum weight:gX51

Vibrational frequencies,n i , and degeneraciesgi

Symmetry n i , cm21 gi Symmetry n i , cm21 gi

A8 n1 3566 1 n10 589 1n2 3037 1 n11 384 1n3 1808 1 n12 180 1n4 1449 1 A9 n13 3076 1n5 1325 1 n14 1243 1n6 1208 1 n15 806 1n7 1047 1 n16 611 1n8 908 1 n17 489 1n9 747 1 n18 ¯

a 1

aInstead of torsional moden18547 cm21, the contributions due to theinternal rotation about C—C bond were calculated from the potential:V(w)5 1

2V3(12cos 3w), wherew is the torsional angle,V35450 cm21.

CH2Br top: Reduced moment of inertia,I r52.8300310239 g cm2, Symmetry number,sm51.

Geometry

r (C—H!51.0960.02 År (O—H!50.9760.02 Å/C—C5O512661°/C—C—O511161.5°/C—C—Br5112.561.5°/C—C—H511262°

r (C—C!51.5160.01 Å /H—C—H5109.561°r (CvO!51.2160.01 Å /C—O—H510661°r (C—O!51.3660.01 Å w(OvC—C—Br)50.0°r (C—Br!51.9560.02 Å w(OvC—O—H)50.0°

Rotational constants in cm21:CH2

79BrCOOH A050.348 921 B050.050 528 C050.044 536CH2

81BrCOOH A050.348 916 B050.050 066 C050.044 176

Product of moments of inertia:I AI BI C528 1783102117 g3 cm6.

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2.1. Enthalpy of Formation

The recommended value of enthalpy of formationgaseous bromoacetic acid,2(383.563.1) kJ mol21, wasobtained by Lagoaet al.1 from experimental measurementThis value is the sum of the enthalpy of formationbromoacetic acid in the crystalline state,D f H°(C2H3BrO2,



f

cr I, 298.15 K!52~466.9861.08! kJ mol21, determinedfrom rotating bomb combustion calorimetry

and the enthalpy of sublimation,DsubH°~C2H3BrO2)5(83.5062.95) kJ mol21, determined from Knudseneffusion experiments. Note that the recommended valuclose to the value predicted by the method of groequations:2


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D fH°~CH2Br–COOH!

5D fH°~CH2Cl–COOH!1D fH°~CH2Br–CH3!

2D fH°~CH2Cl–CH3!5~2427.6!1~261.9!

2~2112.1!52377.4 kJ mol21

~theD fH° values for CH2BrCH3, and CH2ClCH3 were takenfrom compilation by Pedley,3 for CH2ClCOOH—from Ref.1!. A somewhat lower estimate of the enthalpy of formatiof bromoacetic acid,2~39566! kJ mol21 was given by Liaset al.4

2.2. Heat Capacity and Entropy

From their microwave study, van Eijcket al.5 determinedthe rotational constants of three isotopic spec(CH2

79BrCOOH, CH281BrCOOH, and CH2

79BrCOOD!.Although no complete structure could be evaluated fromavailable data, the substitution coordinates of the Br atand the carboxyl H atom were consistent only with thetransstructure with respect to the atoms Br—C—C—O—H. Thisconformation is identical to lowest-energy form of chloracetic acid named ascis-synbecause ofcis configuration forOvC—O—H and Cl—C—CvO groups. Thecis structurewith respect to the atoms Br—C—C—O—H was obtainedby Chenet al.6 from ab initio calculation. However, the geometry of chloroacetic acid calculated by Chenet al.6 wasalso not consistent with that determined from experimenstudies. The trans structure with respect to the atomBr—C—C—O—H ~Cs symmetry! is accepted in this workfor lowest-energy conformer of bromoacetic acid in accowith the microwave data.5 The isotope-weighted value of thproduct of the principal moments of inertia of bromoaceacid is calculated in this work from the rotational constafor CH2

79BrCOOH and CH281BrCOOH.5 Structural param-

eters given above are those estimated by comparisonstructural parameters of CH3COOH,7 CH2ClCH3,

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CH2ClCOOH,9 and CH2BrCH3.10 These structural param

eters yield values for the rotational constants which1.2%–1.6% different from the observed values used incalculations. The difference has a negligible effect onthermodynamic functions.

There is no information on other stable conformers of bmoacetic acid arising from internal rotation around the C—Cbond. van Eijcket al.5 could only conclude that thegaucheconformation, if present, is not significantly higher in enerthan thetransconformation. Their rough estimate of the tosional frequency, 47 cm21, may be compared with 62 cm21

for chloroacetic acid.11 As in the case of chloroacetic acidthe simple potential,

V~w!5 12V3~12cos 3w!,

wherew is the Br—C—CvO torsional angle, is used in thiwork to calculate the internal rotational contributions to tthermodynamic functions of bromoacetic acid. The barrheight for the rotation about the C—C bond is practically thesame in CH2ClCH3 and CH2BrCH3 molecules.12,13 For thatreason, the value ofV3 for bromoacetic acid was acceptedbe the same as that for chloroacetic acid. The value ofreduced moment of inertia for the CH2Br top was derivedfrom structural parameters adopted in this work~see above!.

Vibrational spectra of bromoacetic acid were investigaonly for a solid phase.14–17These vibrational assignments aincomplete and it may be expected that they are muchferent from a gaseous spectrum as in the case of chloroaacid. Fundamental frequencies of gaseous bromoaceticwere estimated in this work by normal coordinate calcutions using the force constants transferred from related cpounds. Simplified force fields for CH3COOH, CH2ClCH3,CH2BrCH3, and CH2ClCOOH were determined using experimental vibrational assignments for these molecules.18–21

37 force constants were used to calculate the vibrationalquencies of bromoacetic acid:

f O—H 7.092 f wag~CvO! 0.310 f C—C,C—C—H 0.199f C—H 4.998 f tors~C—O! 0.183 f C—C,C—C—O 20.425f CvO 14.076 f tors~C—C! 0.028 f C—C,C—C—Br 20.017f C—C 4.101 f C—H,C—H 0.061 f C—C,OvC—C5 f C—C,OvC—O 1.250f C—O 3.891 f C—H,C—C 0.332 f C—O,C—O—H 0.041f C—Br 3.531 f C—H,C—Br 20.402 f C—O,C—C—O 0.296f H—C—H 0.274 f C—C,C—Br 0.377 f C—O,OvC—C5 f C—O,OvC—O 0.605f C—C—H 0.793 f C—C,C—O 0.693 f C—Br,H—C—Br 0.148f C—O—H 0.424 f CvO,C—O 2.221 f C—Br,C—C—Br 0.044f C—C—O 2.465 f CvO,C—C 1.660 f C—H,H—C—Br 20.533f H—C—Br 0.547 f CvO,C—C—O 21.365 f C—H,H—C—H 20.184f C—C—Br 1.042 f CvO,OvC—C5 f CvO,OvC—O 0.687 f C—H,C—C—H 0.216f OvC—C5 f OvC—O 2.312



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~stretching and stretch–stretch interaction constants arunits of mdyn/Å; bend, wagging, and torsion constants arunits of mdyn Å; stretch–bend interaction constants areunits of mdyn!. These constants were transferred froCH3COOH and CH2BrCH3 molecules with corrections madby analyzing the trends in force constants of molecuCH3COOH, CH2ClCH3, and CH2ClCOOH.

The uncertainties in the calculated thermodynamic futions ~Table 1! may reach~3–6! J K21 mol21 for Cp°(T) and~5–12! J K21 mol21 for S°(T). They are caused by the uncertainties in the adopted vibrational frequencies and theproximate treatment of internal rotation.

Ideal gas thermodynamic properties of bromoacetic ahave not been reported previously.

2.3. References

1A. L. C. Lagoa, H. P. Diogo, M. Pilar Dias, M. E. Minas da Piedade,M. P. F. Amaral, M. A. V. Ribeiro da Silva, J. A. Martinho Simo˜es, R. C.Guedes, B. J. Costa Cabral, K. Schwarz, and M. Epple, Chem. Eur.7,483 ~2001!.

2D. R. Stull, E. F. Westrum, and G. C. Sinke,The Chemical Thermodynamics of Organic Compounds~Krieger, Malabar, FL, 1987!; see also the‘‘difference method,’’ N. Cohen, and S. W. Benson, Chem. Rev.93, 2419~1993!.



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id

3J. B. Pedley,Thermochemical Data and Structures of Organic Compounds~Thermodynamics Research Center, College Station, TX, 19!,Vol. I.

4S. G. Lias, J. E. Bartmess, J. F. Liebman, J. L. Holmes, R. D. Levin,W. G. Mallard, J. Phys. Chem. Ref. Data17, Suppl. 1~1988!.

5B. P. van Eijck, H. A. Dijkerman, and J. Smits, J. Mol. Spectrosc.73, 305~1978!.

6L.-T. Chen, G.-J. Chen, and X.-Y. Fu, Chin. J. Chem.13, 10 ~1995!.7B. P. van Eijck, J. van Opheusden, M. M. M. van Schaik, and E. vZoeren, J. Mol. Spectrosc.86, 465 ~1981!.

8M. Hayashi and T. Inagusa, J. Mol. Struct.220, 103 ~1990!.9J. L. Derissen, and J. M. J. M. Bijen, J. Mol. Struct.29, 153 ~1975!.

10T. Inagusa and M. Hayashi, J. Mol. Spectrosc.129, 160 ~1988!.11B. P. van Eijck, A. A. J. Maagdenberg, and J. Wanrooy, J. Mol. Struct.22,

61 ~1974!.12J. R. Durig, W. E. Bucy, L. A. Carreira, and C. J. Wurrey, J. Chem. Ph

60, 1754~1974!.13J. Gripp, H. Dreizler, and R. Schwarz, Z. Naturforsch. A40, 575 ~1985!.14J. E. Katon, T. P. Carll, and F. F. Bentley, Appl. Spectrosc.25, 229

~1971!.15J. E. Katon and D. Sinha, Appl. Spectrosc.25, 497 ~1971!.16J. E. Katon and R. L. Kleinlein, Spectrochim. Acta A29, 791 ~1973!.17P. F. Krause, J. E. Katon, and R. W. Mason, J. Phys. Chem.82, 690

~1978!.18H. Hollenstein and H. H. Gu¨nthard, J. Mol. Spectrosc.84, 457 ~1980!.19S. Suzuki and A. B. Dempster, J. Mol. Struct.32, 339 ~1976!.20S. Suzuki, J. L. Bribes, and R. Gaufres, J. Mol. Spectrosc.47, 118~1973!.21 J. Nieminen, M. Pettersson, and M. Ra¨sanen, J. Phys. Chem.97, 10925

~1993!.



3. Chloroacetic Acid, CH 2Cl—COOH

Chloroacetic acid (C2H3ClO2) Ideal gas Mr594.4975D fH°(0 K)52416.061.0 kJ mol21

S°(298.15 K)5325.965.0 J K21 mol21 D fH°(298.15 K!52427.661.0 kJ mol21

Molecular constantsPoint group:Cs Symmetry number:s51Ground electronic state: X 1A Energy:eX50 cm21 Quantum weight:gX51

TABLE 1. Ideal gas thermodynamic properties of bromoacetic acid C2H3BrO2~g! at the standard state pressure,p°50.1 MPa~Tr5298.15 K)

T~K!

Cp°~J K21 mol21!

S°~J K21 mol21!

2@G°2H°(Tr)#/T~J K21 mol21!

H°2H°(Tr)~kJ mol21!

D fH°~kJ mol21!

D fG°~kJ mol21! log Kf°

0 0.000 0.000 ` 216.862 2364.616 2364.616 `25 36.587 211.762 852.075 216.008 2365.365 2365.150 762.91950 41.371 238.698 539.288 215.029 2366.712 2364.466 380.74675 45.202 256.212 442.164 213.946 2368.184 2363.016 252.820

100 48.832 269.713 397.423 212.771 2369.448 2361.099 188.614

150 56.415 290.927 358.541 210.142 2371.701 2356.428 124.116180 61.214 301.635 348.180 28.378 2372.997 2353.251 102.508190 62.843 304.988 345.818 27.758 2373.427 2352.142 96.808200 64.482 308.253 343.859 27.121 2373.854 2351.012 91.672

210 66.128 311.439 342.239 26.468 2374.281 2349.858 87.020220 67.778 314.553 340.910 25.799 2374.706 2348.686 82.786230 69.431 317.602 339.831 25.113 2375.130 2347.493 78.916240 71.083 320.592 338.967 24.410 2375.553 2346.282 75.364250 72.731 323.527 338.291 23.691 2375.975 2345.055 72.094

260 74.374 326.412 337.779 22.955 2376.398 2343.809 69.070270 76.007 329.250 337.411 22.204 2382.140 2342.466 66.252280 77.630 332.043 337.169 21.435 2382.632 2340.987 63.610290 79.240 334.795 337.040 20.651 2383.115 2339.491 61.147

298.15 80.540 337.010 337.010 0.0002383.500 2338.262 59.261

300 80.834 337.509 337.011 0.149 2383.587 2337.981 58.846350 88.515 350.553 338.023 4.385 2400.269 2329.432 49.164400 95.600 362.842 340.365 8.991 2401.362 2319.235 41.687450 102.021 374.480 343.514 13.934 2402.305 2308.911 35.857500 107.785 385.532 347.168 19.182 2403.114 2298.489 31.182

600 117.569 406.081 355.302 30.468 2404.395 2277.439 24.153700 125.486 424.820 363.915 42.634 2405.305 2256.204 19.118800 132.017 442.016 372.617 55.519 2405.904 2234.859 15.334900 137.498 457.891 381.222 69.002 2406.239 2213.457 12.388

1000 142.157 472.625 389.634 82.9912406.354 2192.028 10.030

1100 146.150 486.366 397.810 97.4112406.281 2170.598 8.1011200 149.592 499.234 405.732 112.2032406.053 2149.181 6.4941300 152.573 511.328 413.394 127.3152405.702 2127.785 5.1341400 155.164 522.732 420.800 142.7042405.257 2106.425 3.9711500 157.423 533.516 427.958 158.3362404.734 285.097 2.963

1600 159.399 543.741 434.879 174.1802404.160 263.786 2.0821700 161.134 553.457 441.570 190.2082403.549 242.535 1.3071800 162.662 562.712 448.045 206.4002402.914 221.313 0.6181900 164.013 571.543 454.315 222.7352402.270 20.130 0.0042000 165.210 579.987 460.389 239.1972401.625 21.019 20.549


Downloaded 02 Jul 2012 to 129.6.105.191. Redistribution subject to AIP license or copyright; see http://jpcrd.aip.org/about/rights_and_permissions




A8 n1 3566 1 n10 596 1n2 3019 1 n11 397 1n3 1806 1 n12 216 1n4 1428 1 A9 n13 3076 1n5 1354 1 n14 1193 1n6 1274 1 n15 929 1n7 1111 1 n16 611 1n8 891 1 n17 492 1n9 792 1 n18 ¯

a 1aInstead of torsional moden18562 cm21, the contributions due to theinternal rotation about C—C bond were calculated from the potentialV(w)5 1

2V3(12cos 3w), where w is the torsional angle andV3

5450 cm21.

CH2Cl top: Reduced moment of inertia,I r52.4514310239 g cm2, Symmetry number,sm51.

Geometry

r (C—H!51.0960.02 År (O—H!50.9760.015 Å/C—CvO5126.160.5°/C—C—O5110.660.4°/C—C—Cl5112.560.4°/C—C—H5109.5~assumed!

r (C—C!51.50860.006 Å /H—C—H5109.5~assumed!r (CvO!51.22360.004 Å /C—O—H5105.861.1°r (C—O!51.35260.005 Å w(OvC—C—Cl)50.0°r (C—Cl!51.77860.005 Å w(OvC—O—H)50.0°

Rotational constants in cm21:A050.350 738 B050.078 433 C050.064 913


oe

-of

f

u

o-

omb

ionb

ein


The recommended value of the enthalpy of formationgaseous chloroacetic acid at 298.15 K is the sum of thethalpy of formation of thea form of the solid and the enthalpy of sublimation both at 298.15 K. The valueD fH°(298.15 K,a-cr)52(509.7460.49) kJ mol21 is fromthe work of Lagoaet al.1 who measured the enthalpy ocombustion of thea form of the solid with a rotating bombcalorimeter. Their result is in agreement with the resD fH°(298.15 K,cr)52(510.568.3) kJ mol21 of Smithet al.2 from their re-evaluation of earlier static bomb calrimetry measurements.3

The enthalpy of sublimation,DsubH°(298.15 K)5(82.1960.92) kJ mol21, used here is also from Lagoaet al.,1 and isderived from vapor pressures of the solid obtained frKnudsen effusion experiments. This value is supportedapplication of Hess’s law where the enthalpy of sublimatis the sum of five processes at the standard pressure of 1Thus,



fn-

lt

y

ar.

DsubH° ~298.15 K!

5@H°~cr,334.8 K!2H°~cr,298.15 K!#

1D fusH°~334.8 K!1@H°~1,462 K!2H°~1,334.8 K!#

1DvapH°~462 K!2@H°~g,462 K!

2H°~cr,298.15 K!#580.962.3 kJ mol21.

The first and third terms@H°(T2)2H°(T1)#'Cp°(cr)3DT are (3.960.1) and (21.660.5) kJ mol21, respectively,based onCp°(cr)5(106.762.0) J K21 mol21 from differen-tial scanning calorimetery~DSC! measurements1 andCp°(1)5(168.964.0) J K21 mol21 from Pickering.4 @Thisvalue ofCp°(cr) differs significantly from the average valuof 144 J K21 mol21 over the range of 288–318 K reportedPickering4 and adopted in NIST Chemistry WebBook5 andDonalski and Hearing.6 The value ofCp°(1)5179.9 J K21

mol21 from Urazovskii and Sidorov7 was not used.#D fusH°(334.8 K)516.360.7 kJ mol21 from DSCmeasurements1 while DvapH°(462 K)5(54.562.0) kJ mol21


e,


Dow

TABLE 2. Ideal gas thermodynamic properties of chloroacetic acid C2H3ClO2(g) at the standard state pressurp°50.1 MPa~Tr5298.15 K!

T~K!

Cp°~J K21 mol21!

S°~J K21 mol21!

2(G°2H°(Tr))/T~J K21 mol21!


D fH°~kJ mol21!


0 0.000 0.000 ` 216.514 2416.032 2416.032 `25 36.170 203.287 829.838 215.664 2417.069 2414.897 866.85850 40.498 229.818 523.832 214.701 2418.460 2412.226 430.63975 44.011 246.902 428.827 213.644 2419.862 2408.793 284.702

100 47.641 260.056 385.047 212.499 2420.999 2404.926 211.506

150 55.261 280.802 346.988 29.928 2422.890 2396.468 138.059180 59.960 291.292 336.846 28.200 2423.925 2391.086 113.487190 61.543 294.576 334.536 27.592 2424.261 2389.252 107.010200 63.133 297.773 332.618 26.969 2424.594 2387.401 101.176

210 64.730 300.892 331.033 26.330 2424.922 2385.533 95.894220 66.332 303.940 329.733 25.674 2425.246 2383.649 91.088230 67.938 306.924 328.676 25.003 2425.565 2381.752 86.696240 69.546 309.849 327.831 24.316 2425.880 2379.841 82.668250 71.155 312.721 327.169 23.612 2426.190 2377.915 78.959

260 72.762 315.543 326.668 22.892 2426.493 2375.978 75.533270 74.365 318.319 326.308 22.157 2426.792 2374.030 72.359280 75.962 321.053 326.072 21.405 2427.085 2372.071 69.409290 77.551 323.746 325.945 20.638 2427.372 2370.101 66.661

298.15 78.838 325.913 325.913 0.0002427.600 2368.487 64.556

300 79.129 326.402 325.916 0.146 2427.651 2368.121 64.094350 86.790 339.180 326.908 4.296 2428.953 2358.094 53.441400 93.933 351.242 329.202 8.816 2430.094 2347.892 45.429450 100.456 362.689 332.293 13.678 2431.085 2337.556 39.181500 106.342 373.583 335.881 18.851 2431.941 2327.116 34.173

600 116.373 393.891 343.883 30.005 2433.310 2306.019 26.641700 124.509 412.462 352.372 42.063 2434.295 2284.721 21.246800 131.218 429.540 360.965 54.859 2434.957 2263.304 17.192900 136.840 445.329 369.473 68.270 2435.342 2241.822 14.035

1000 141.610 460.000 377.801 82.1992435.499 2220.311 11.508

1100 145.691 473.693 385.903 96.5692435.459 2198.792 9.4401200 149.204 486.524 393.760 111.3182435.259 2177.285 7.7171300 152.241 498.590 401.364 126.3942434.930 2155.797 6.2601400 154.877 509.971 408.719 141.7532434.500 2134.342 5.0121500 157.173 520.736 415.831 157.3582433.991 2112.918 3.932

1600 159.180 530.946 422.709 173.1782433.426 291.512 2.9871700 160.940 540.650 429.364 189.1862432.819 270.164 2.1561800 162.490 549.894 435.805 205.3592432.185 248.846 1.4171900 163.858 558.716 442.044 221.6782431.536 227.566 0.7582000 165.071 567.153 448.090 238.1252430.883 26.322 0.165

n

a

b

c

hithrre-

r oftronith

of

nednion

is derived from vapor pressure data over a temperature rafrom 385.45 K to the normal boiling point.9,10 @Other valuesof D fusH°(334.8 K) are 16.3 kJ mol21 from Pickering4 and12.3 kJ mol21 from Acree.8# The value @H°(g,462 K)2H°(cr,298.15 K)#5(15.460.7) kJ mol21 is interpolatedfrom Table 2 of the present work. This corrects the estimDsubH°(298.15)5(75.364.2) kJ mol21 by Cox andPilcher5,6,11 based onD fusH°(334 K)519.4 kJ mol21 fromSteiner and Johnson12 and DvapH°(462 K)554.5 kJ mol21

mentioned above. Cox and Pilcher also use Hess’s law,assume that the values ofCp° for the gas, liquid, and solidphases are equal.


According to the experimental13–18 and theoretical15,17–19

studies, the lowest-energy conformer of chloroacetic a

nloaded 02 Jul 2012 to 129.6.105.191. Redistribution subject to AIP lic

ge

te

ut

id

(CH2Cl—CO—OH) has thecis-synstructure~Cs symmetry!with the cis configuration for the carboxylic group and witthe chlorine atom lying in the carboxylic plane eclipsed wthe carbonyl group. The second more stable form cosponds to thecis-gauchestructure with a Cl—C—CvOangle of;130° ~C1 symmetry!. This form differs fromcis-synby internal rotation of the CH2Cl group about the C—Cbond. Structural parameters of the most stable conformechloroacetic acid were determined by gas phase elecdiffraction.14 These parameters are in good agreement wresults fromab initio18,19 and molecular mechanics15 calcu-lations. In this work, the product of the principal momentsinertia for the most stablecis-synconformer of chloroaceticacid was calculated using rotational constants determifrom the microwave study.13 Structural parameters giveabove are those obtained from the electron diffract



ri

on-

in

re

nthin

sbH0

raa

u

fa-fal

eatihc-

th

o

d

--

nc

freot

as

n--

ncyeof

L.

J.

nd.

er

l-

oc.,

.

it,


study.14 These parameters reproduce the product of the pcipal moments of inertia calculated above within 3%.

Three conformations with respect to internal rotatiaround the C—C bond were found from an electron diffraction investigation,14 namely, 56% of acis-synconformation,30% of a cis-gaucheconformation with the CH2Cl grouprotated 131° from the former position, and the remain14% of acis-gaucheconformation with 79° rotation of theCH2Cl group. Three conformers of chloroacetic acid weidentified by vibrational spectroscopy.15–18 Two of themwere cis-synand cis-gauchein agreement with the electrodiffraction data. The third stable form was found to havetrans structure, in which the carboxylic hydrogen atom isthe transposition with respect to the CvO bond.Transcon-formers arise from rotation of the OH group about the C—Obond. Ab initio calculations17,18 and molecular mechanicstudies15 strongly suggest that the third stable form shouldthe trans form. The barrier height for the rotation of the Ogroup around the C—O bond is predicted to be 1700–350cm21.16–18Due to the height of this barrier and the tempeture range of the present tabulation, this internal rotation wignored in this work.

Two cis conformers with respect to internal rotation abothe C—C bond were considered in this work: thecis-synconformer ofCs symmetry and two enantiomeric forms ocis-gaucheconformer ofC1 symmetry. The observed datand the calculations14,16–18 consistently predict a slight energy preference for thecis-synform and a small barrier o~400–450! cm21 for its interconversion. The simple potenti

V~w!5 12V3~12cos 3w!,

wherew is the Cl—C—CvO torsional angle, is used herfor a very approximate calculation of the internal rotationcontributions to the thermodynamic functions of chloroaceacid. The value of the reduced moment of inertia for tCH2Cl top was derived from the electron diffraction strutural parameters.14

Vibrational spectra of chloroacetic acid were studied inliquid and solid phases,15,20,21in the vapor22 and matrix.16,18

The fundamental frequencies adopted in this work are thderived by Nieminenet al.18 from matrix isolation infraredspectra (n1 ,n3–n5 ,n7 ,n8 ,n9 ,n15–n17) and ab initio calcu-lation (n2 ,n6 ,n10–n14). These frequencies are in gooagreement with results of normal coordinate analysis,22 mo-lecular mechanics,15 and ab initio17 calculations. The valuefor the torsional frequency,n18, was estimated from the microwave spectrum13 and it coincides with the value calculated by theab initio method.18

The uncertainties in the calculated thermodynamic futions~Table 2! may amount to as much as~3–5! J K21 mol21

for Cp°(T) and 5–10 J K21 mol21 for S°(T). They arecaused by the uncertainties in the adopted vibrationalquencies and the approximate treatment of the internal rtion.

Thermodynamic properties of chloroacetic acid were cculated earlier by Banerjee23 using molecular constantknown at that time. A value for the barrier height of;1750



n-

g

e

e

-s

t

lce

e

se

-

-a-

l-

cm21 was adopted for calculating the internal rotation cotributions of the CH2Cl and OH groups. The difference between the values ofCp°(T) andS°(T) given here and thoseby Banerjee23 amounts to 57 and 35 J K21 mol21, respec-tively. Such a difference could not be due to the discrepain molecular constants used. The calculation of Banerje23

seems to be in error. The rough estimate by the methodgroup equations,

Cp°~CH2Cl—COOH!

5Cp°~CH3—COOH!1Cp°~CH2Cl—CH3!

2Cp°~CH3—CH3!

563.4162.6252.5573.5 JK21 mol21,

is close to the value obtained in this work~78.8 J K21 mol21!and is very different from the value of Banerjee23 ~136.0J K21 mol21!. The calculation of Banerjee23 is reproduced inthe reference book of Frenkelet al.24

3.3. References

1A. L. C. Lagoa, H. P. Diogo, M. Pilar Dias, M. E. Minas da Piedade,M. P. F. Amaral, M. A. V. Ribeiro da Silva, J. A. Martinho Simo˜es, R. C.Guedes, B. J. Costa Cabral, K. Schwarz, and M. Epple, Chem. Eur.7,483 ~2001!.

2L. Smith, L. Bjellerup, S. Krook, and H. Westermark, Acta Chem. Sca7, 65 ~1953!.

3E. Schjanberg, Z. Phys. Chem. Abt. A172, 197 ~1935!.4S. U. Pickering, J. Chem. Soc.67, 664 ~1895!.5NIST Chemistry WebBook, NIST Standard Reference Database Numb69, edited by W. G. Mallard and P. J. Lindstrom~National Institute ofStandards and Technology, Gaithersburg, MD, November 1998! ~http://webbook.nist.gov/chemistry!.

6E. S. Domalski and E. D. Hearing, J. Phys. Chem. Ref. Data25, 1 ~1996!.7S. S. Urazovskii and I. A. Sidorov, Dokl. Akad. Nauk SSSR70, 859~1950!.

8W. E. Acree, Jr., Thermochim. Acta189, 37 ~1991!.9R. R. Dreisbach and S. A. Shrader, Ind. Eng. Chem.41, 2879~1949!.

10D. R. Stull, Ind. Eng. Chem.39, 517 ~1947!.11J. D. Cox and G. Pilcher,Thermochemistry of Organic and Organometa

lic Compounds~Academic, London, 1970!.12L. E. Steiner and J. Johnston, J. Phys. Chem.32, 912 ~1928!.13B. P. van Eijck, A. A. J. Maagdenberg, and J. Wanrooy, J. Mol. Struct.22,

61 ~1974!.14J. L. Derissen and J. M. J. M. Bijen, J. Mol. Struct.29, 153 ~1975!.15R. Fausto and J. J. C. Teixeira-Dias, J. Mol. Struct.144, 225 ~1986!.16A. Kulbida and A. Nosov, J. Mol. Struct.265, 17 ~1992!.17R. Fausto, J. J. C. Teixeira-Dias, and F. P. S. C. Gil, J. Chem. S

Faraday Trans.89, 3235~1993!.18J. Nieminen, M. Pettersson, and M. Ra¨sanen, J. Phys. Chem.97, 10925

~1993!.19K. E. Edgecombe and R. J. Boyd, Can. J. Chem.62, 2881~1984!.20J. R. Barcelo, M. P. Jorge, and C. Otero, J. Chem. Phys.28, 1230~1958!.21R. J. Jakobsen and J. E. Katon, Spectrochim. Acta A29, 1953~1973!.22L. I. Kozhevina, V. M. Belobrov, V. A. Panichkina, and E. V. Titov, Zh

Strukt. Khim.20, 405 ~1979!.23S. C. Banerjee, Br. Chem. Eng.14, 671 ~1969!.24M. Frenkel, G. J. Kabo, K. N. Marsh, G. N. Roganov, and R. C. Wilho

Thermodynamics of Organic Compounds in the Gas State~Thermodynam-ics Research Center, College Station, TX, 1994!, Vol. I, p. 341.



4. Oxopropanedinitrile, NC ACOACN

Oxopropanedinitrile (C3N2O) Ideal gas Mr580.0458D fH°(0 K)5246.566.4 kJ mol21


Molecular constantsPoint group:C2n Symmetry number:s52Ground electronic state:X 1A1

Energy: eX50 cm21 Quantum weight:gX51



A1 n1 2230 1 B1 n7 712 1n2 1711 1 n8 208.2 1n3 712 1 B2 n9 2230 1n4 553 1 n10 1124 1n5 127.5 1 n11 550 1

A2 n6 307 1 n12 245.2 1

Geometry

r ~CvO!51.20460.005 År ~C–C!51.46160.005 År ~CwN!51.15960.015 Å/C—C—C5114.760.5°/C—CwN5179.260.5°

Rotational constants in cm21:A050.225 529 B050.097 556 C050.067 980.


ob

.

ete,

ainvelt

ab-

rd

inlvi-as-f

ent

y-

nc-


The recommended value of enthalpy of formation of oxpropanedinitrile is based on calorimetric measurementsvon Glemser and Ha¨usser1 as evaluated by Cox and Pilcher2


Spectroscopic,3–10 electron diffraction,11 andtheoretical12–20 investigations have shown that oxopropandinitrile, CO~CN!2, is planar in its ground electronic staX 1A1 and belongs to theC2n symmetry group. In this workthe product of the principal moments of inertia of CO~CN!2

was calculated using the rotational constants determinedmicrowave spectroscopy.4 In the absence of isotopic data,unique set of geometrical parameters cannot be obtafrom the microwave spectrum. Structural parameters giabove arer e parameters determined by combining the resuof electron diffraction, microwave spectroscopy, andab ini-tio calculations.20 These parameters give values for rotationconstants which are only 0.3%–0.9% different from the oserved values. The C—C[N chain appears to be nearly lin


-y

-

by

edns

l-

ear, the deviation from linearity being 0.8°. A small inwabend ~0.5°–2°! was also found by ab initiocalculations12,13,19 but is contradicted byab initio calcula-tions of Tyrrell15 where the C—C[N is bent outwards by1.2°.

Vibrational spectra of oxopropanedinitrile were studiedthe gas, liquid, and solid phase5–10 but there are still severauncertainties in the assignment of the fundamentals. Thebrational frequencies accepted in this work are thosesigned by Milleret al.9 from infrared and Raman spectra ogaseous and liquid oxopropanedinitrile. Their assignmwas supported byab initio calculation.15

According to the semiempirical calculation,21 the excitedelectronic states of CO~CN!2 lie above 24 000 cm21. Theyare not taken into account in the calculation of thermodnamic functions.

The uncertainties in the calculated thermodynamic futions ~Table 3!are estimated to be~1–2! J K21 mol21 forCp°(T) and ~1–2.5! J K21 mol21 for S°(T).

Thermodynamic properties of CO~CN!2 were calculatedearlier by Natarajan and Rajendran22 using electron diffrac-



fofnnoo

o

l-

.

M


tion structural parameters11 and the vibrational assignment oBates and Smith.8 The numerical data in the four columnsthe table of thermodynamic functions in Natarajan aRajendran22 are transposed. Moreover, these functions docorrespond to the molecular constants used by the authThe difference between theCp°(T) andS°(T) values givenhere and those by Natarajan and Rajendran22 amounts to 20J K21 mol21 and could not be due to the discrepancy in mlecular constants used.

4.3. References

1O. von Glemser and V. Ha¨usser, Z. Naturforsch. B3, 159 ~1948!.2J. D. Cox and G. Pilcher,Thermochemistry of Organic and Organometalic Compounds~Academic, London, 1970!; see also J. B. Pedley,Ther-mochemical Data and Structures of Organic Compounds~Thermodynam-ics Research Center, College Station, TX, 1994!, Vol. I.

3J. F. Westerkamp, Bol. Acad. Nacl. Cienc. Argen.42, 191 ~1961!.4R. M. Lees, Can, J. Chem.49, 367 ~1971!.5A. Tramer and K. L. Wierzchowski, Bull. Acad. Pol. Sci., Classe III5,411 ~1957!.

6A. Tramer and K. L. Wierzchowski, Bull. Acad. Pol. Sci., Classe III5,417 ~1957!.



dt

rs.

-

7J. Prochorov, A. Tramer, and K. L. Wierzchowski, J. Mol. Spectorsc.19,45 ~1966!.

8J. B. Bates and W. H. Smith, Spectrochim. Acta A26, 455 ~1970!.9F. A. Miller, B. M. Harney, and J. Tyrrell, Spectrochim. Acta A27, 1003~1971!.

10D. M. Thomas, J. B. Bates, E. R. Lippincott, Indian. J. Pure Appl. Phys9,969 ~1971!.

11V. Typke, M. Dakkouri, and F. Schlumberger, J. Mol. Struct.62, 111~1980!.

12W. Kosmus, K. Kalcher, and G. D. Fleming, J. Mol. Struct: THEOCHE89, 317 ~1982!.

13K. Siam, M. Dakkouri, J. D. Ewbank, and L. Scha¨fer, J. Mol. Struct:THEOCHEM 204, 291 ~1990!.

14M. Dakkouri, Struct. Chem.1, 179 ~1990!.15J. Tyrrell, J. Mol. Struct.: THEOCHEM231, 87 ~1991!.16M. Dakkouri, J. Mol. Struct.: THEOCHEM258, 401 ~1992!.17J. Tyrrell, J. Mol. Struct.: THEOCHEM258, 403 ~1992!.18J. L. G. De Paz and M. Yanez, J. Mol. Struct.: THEOCHEM107, 59

~1984!.19M. H. Palmer, J. Mol. Struct.: THEOCHEM200, 1 ~1989!.20J. Demaison, G. Wlodarczak, H. Ru¨ck, K. H. Wiedenmann, and H. D.

Rudolph, J. Mol. Struct.:376, 399 ~1996!.21C. H. Warren and C. Ching, Theor. Chim. Acta30, 1 ~1973!.22A. Natarajan and S. Rajendran, Can. J. Spectorsc.26, 229 ~1981!.



5. Glycolic Acid, HO ACH2ACOOH

Glycolic acid (C2H4O3) Ideal gas Mr576.0518D fH°(0 K)52567.9610.0 kJ mol21


Molecular constants

Point group:C1 Symmetry number:s51 Number of optical isomers:n52Ground electronic state:X 1A Energy:eX50 cm21 Quantum weight:gX51

TABLE 3. Ideal gas thermodynamic properties of oxopropanedinitrile C3N2O(g) at the standard state pressure,p°50.1 MPa~Tr5298.15 K)

T~K!

Cp°~J K21 mol21!

S°~J K21 mol21!

2(G°2H°(Tr))/T~J K21 mol21!


D fH°~kJ mol21!

D fG°~kJ mol21! log Kfs°

0 0.000 0.000 ` 217.147 246.525 246.525 `25 33.558 186.154 838.755 216.315 246.274 246.273 2514.55350 37.466 210.389 519.096 215.435 246.040 246.369 2257.37675 43.512 226.703 419.028 214.424 245.902 246.567 2171.722

100 49.389 240.041 372.658 213.262 245.872 246.796 2128.911

150 59.439 262.030 332.251 210.533 246.052 247.230 286.092180 64.718 273.341 321.506 28.670 246.268 247.447 271.806190 66.369 276.884 319.064 28.014 246.354 247.510 268.044200 67.965 280.329 317.042 27.342 246.444 247.569 264.657

210 69.506 283.683 315.374 26.655 246.539 247.623 261.592220 70.992 286.951 314.008 25.953 246.639 247.672 258.804230 72.425 290.138 312.901 25.235 246.742 247.716 256.257240 73.804 293.250 312.018 24.504 246.848 247.756 253.922250 75.131 296.290 311.328 23.760 246.956 247.792 251.773

260 76.408 299.262 310.807 23.002 247.067 247.823 249.788270 77.636 302.169 310.434 22.232 247.179 247.851 247.949280 78.818 305.013 310.189 21.449 247.292 247.873 246.241290 79.956 307.799 310.059 20.655 247.407 247.892 244.650

298.15 80.853 310.028 310.028 0.000 247.500 247.905 243.431

300 81.052 310.529 310.029 0.150 247.521 247.907 243.164350 85.979 323.404 311.035 4.329 248.092 247.925 237.000400 90.165 335.165 313.327 8.735 248.634 247.864 232.367450 93.807 346.000 316.363 13.337 249.125 247.738 228.756500 97.037 356.054 319.835 18.109 249.559 247.560 225.862

600 102.566 374.251 327.420 28.099 250.253 247.090 221.511700 107.123 390.415 335.286 38.590 250.757 246.521 218.395800 110.898 404.974 343.102 49.497 251.123 245.892 216.055900 114.022 418.222 350.724 60.748 251.390 245.219 214.232

1000 116.608 430.373 358.090 72.284 251.851 244.520 212.772

1100 118.754 441.591 365.177 84.055 251.719 243.809 211.5771200 120.542 452.003 371.984 96.023 251.810 243.084 210.5811300 122.038 461.712 378.517 108.154 251.862 242.358 29.7381400 123.297 470.804 384.788 120.422 251.871 241.623 29.0151500 124.364 479.348 390.810 132.807 251.846 240.895 28.389

1600 125.273 487.404 396.598 145.290 251.779 240.197 27.8421700 126.052 495.022 402.165 157.857 251.679 239.474 27.3581800 126.724 502.247 407.526 170.497 251.541 238.765 26.9291900 127.307 509.114 412.694 183.199 251.366 238.058 26.5452000 127.815 515.658 417.680 195.956 251.156 237.363 26.199






A8 n1 3561 1 n12 642 1n2 3561 1 n13 468 1n3 2928 1 n14 270 1n4 1774 1 A9 n15 2919 1n5 1452 1 n16 1231 1n6 1439 1 n17 1019 1n7 1332 1 n18 621 1n8 1265 1 n19 495 1n9 1143 1 n20 281 1n10 1090 1 n21 ¯

a 1n11 854 1

aInstead of torsional moden215152 cm21, the contributions due to theinternal rotation round the C—C bond were calculated from the potentialV(w)5 1

2(n518 Vn(12cosnw), where w is the torsional angle,V1

5971.1, V251192.6, V352196.0, V452244.1, V55137.1, V652173.5,V75118.8, andV85248.0 ~in cm21!.

COOH top: Reduced moment of inertia,I r51.9292310239g cm2, Symmetry number,sm51.

Geometry

r (C1—C2!51.49560.006 År (C1—O3!51.34960.006 År (C1vO4!51.21060.006 År (C2—O5!51.40660.004 År (O3—H9!50.98960.019 År (O5—H8!50.95660.003 År (C2—H6,7!51.09760.003 Å

/C2—C1—O35112.660.5°/C2—C1vO45124.260.4°/C1—C2—O55111.360.4°/O5—C2—H6,75110.660.3°/C1—C2—H6,75108.860.3°/C1—O3—H95105.561.1°/C2—O5—H85105.260.1°


Product of moments of inertia:I AI BI C545553102117 g3 cm6.

Other stable conformers: Point group Symmetry number,s Number of optical isomers,n Energy, cm21

C1 1 2 1200C1 1 2 1300

are

i-

th


No experimental or theoretical data on enthalpy of formtion of gaseous glycolic acid are known from the literatuThe value accepted in this work,D fH° (298.15 K)52(583610) kJ mol21, is based on two estimates by addtivity methods.

The first value was estimated by group additivity usingequation

D fH°~HO—CH2—COOH!

5D fH°@O—~H!~C!#1D fH°@C—~H!2~CO!~O!#

1D fH°@CO—~C!~O!#1D fH°@O—~CO!~H!#



-.

e

5~2158.6!1~233.5!1~2147.3!1~2241.8!

52581.2 kJ mol21

with group values generated by Cohen1 except for the miss-ing value for the@C—~H!2~CO!~O!# group. The latter wasevaluated from values known for related groups:

D fH°@C—~H!2~CO!~O!#

5D fH°@C—~H!2~CO!~C!#

1D fH°@C—~H!~CO!~C!~O!#

2D fH°@C—~H!~CO!~C!2#


y

rdinhyther

ily

l

-

su.

myepeThd

erde

rg

f

s,

ym-theob-

eene

ndmshe

eingec-reso-

de-

be93t-l

t-

ata

ier

tion

the3

he

nd

al


5~221.8!1~218.8!

2~27.1!5233.5 kJ mol21.

The otherD fH° value of glycolic acid may be predicted bthe method of group equations2 using

D fH°~HO—CH2—COOH!

5D fH°~CH3—COOH!1D fH°~HO—CH2—CH3!

2D fH°~CH3—CH3!

5~2432.8!1~2235.2!

2~283.8!52584.2 kJ mol21.

Values for D fH° for CH3COOH, CH3CH2OH, and C2H6

were taken from a compilation by Pedley.3 A value interme-diate between the above two estimates was assigned toenthalpy of formation of glycolic acid.


From microwave spectroscopic studies,4–6 the lowest-energy structure of glycolic acid was concluded to be ofCs

symmetry with the alcoholic hydroxyl group pointing towathe carbonyl oxygen of carboxyl group. This structurevolves the intramolecular bonding between the alcoholdrogen and the carbonyl oxygen. With the exception ofmethylene hydrogen all the atoms in the molecule wfound to be coplanar. The pathways and energy barriersvolved in possible conformational interconversions of gcolic acid were investigated byab initio calculations.7–12

Along with rotamers ofcis-glycolic acid, where the carbonygroup has thecis conformation with its hydroxyl group, theconformers oftrans-glycolic acid were predicted from theoretical studies. Based on electron diffraction data13 the sec-ond lowest conformer has been assigned to acis-glycolicacid with hydrogen bonding between two hydroxyl groupThe energy difference between these conformers was foto be 1470 cm21 based on fitting to the diffraction dataHowever, this result is in conflict with theoretical data8,10–12

predicting the energy difference for the two lowest conforers to be 530–880 cm21. Moreover, it has been shown bGodfreyet al.11 from ab initio calculations and a microwavstudy that the two experimentally observed glycolic acid scies need not necessarily be the two of lowest energy.authors in Ref. 11 have assigned the second conformertected by microwave spectroscopy as thetrans-glycolic acidwith relative energy of;1200 cm21. This conformer wasstructurally quite similar to thetrans-glycolic acid conformerdetected earlier in an infrared matrix isolation study.9

The symmetries and relative stabilities of the conformof glycolic acid adopted in this work are based on thetailed ab initio calculations of Godfreyet al.11 who testedsome of their predictions experimentally. The lowest ene


the

--een--

.nd

-

-ee-

s-

y

conformer identified byab initio calculation11 was found tobe theC1 conformer which is a slightly twisted version othe Cs from detected by microwave spectroscopy.4–6 A con-former of C1 symmetry exists in two enantiomeric formand there is a small barrier~1.5 cm21! between this con-former and its mirror image where the saddle point is ofCs

symmetry. The ground vibrational state energy in these smetric double wells may be greater than the height ofsaddle point, in which case the effective structure of theserved conformer would closely match theCs conformer ofthe saddle point. It should be noted that the decision betwassigningCs or C1 symmetry is of great importance for thcalculation of the thermodynamic functions. ForC1 symme-try the termR ln 2 must be added to both the entropy aGibbs energy function because two optically isomeric forare present.C1 symmetry was accepted in this work as tpoint group of the lowest-energy form of glycolic acid.

The product of the principal moments of inertia for thmost stable conformer of glycolic acid was calculated usthe rotational constants determined from microwave sptrum investigation.4 Structural parameters given above wedetermined from the microwave spectra of normal and itopically substituted species of glycolic acid.5 In general,these geometric molecular parameters are close to thosetermined from electron diffraction analysis13 and ab initiocalculations.7,8,10

According to theab initio calculation of Godfreyet al.11

the C1 conformer, a twisted version ofcis-form with hydro-gen bonding between the hydroxyl groups, is expected tothe second lowest conformer with relative energy of 6cm21. In this work, the energy profile between two lowesenergy C1 conformers11 was approximated by a potentiaenergy function for internal rotation around the C—C bond,

V~w!51

2 (n51

8

Vn~12cosnw!,

wherew is the O4—C1—C2—C5 torsional angle. The eighcoefficients (Vn) in the expansion for this moderately complex potential energy function were determined using dfrom the ab initio calculation by Godfreyet al.11 The flatminimum at w50° corresponds to the lowest-energyC1

conformer of glycolic acid. Because of the small barrheight between its enantiomeric forms~1.5 cm21!, they arenot represented by the above potential and their contribuwas taken into account by adding theR ln 2 to the entropyand Gibbs energy function. The barrier of 1658 cm21 atf5110° separates the lowest-energy conformer fromsecondC1 stable conformer with an energy minimum of 69cm21 at f5155°. There is a barrier of 338 cm21 at w5180° between this conformer and its mirror image. Tvalue of the reduced moment of inertiaI r was calculatedusing the molecular structural parameters of Blom aBauder.5 The next most abundantC1 conformers with rela-tive energies of;1200 and 1300 cm21 ~Goldfrey et al.11!were taken into account in this work ignoring their intern



thw-i

or-oropol.

th

nc

olic

v

-94

.


rotation and adopting their molecular constants to besame as those of the basic conformer. The conformersenergies of about 2000 cm21 and higher were ignored because of their negligible contribution to the thermodynamfunctions.

Hollensteinet al.14 have measured the infrared spectra11 isotopic modifications of glycolic acid isolated in an agon matrix and have evaluated the transferable valence ffield that reproduced the observed frequencies and isotshifts very satisfactorily. The vibrational assignment by Hlensteinet al.14 for Cs symmetry is adopted in this workFundamentals of glycolic acid calculated by anab initiomethod10 are close to experimental values except forlow-frequency torsional mode.

The uncertainties in the calculated thermodynamic futions ~Table 4! may reach~3–5! J K21 mol21 for Cp°(T) and~5–10! J K21 mol21 for S°(T). They are essentially due tthe approximate treatment of internal rotation in glycoacid.

Ideal gas thermodynamic properties of glycolic acid hanot been reported previously.



eith

c

f

ceic

-

e

-

e

5.3. References

1N. Cohen, J. Phys. Chem. Ref. Data25, 1411~1996!.2D. R. Stull, E. F. Westrum, and G. C. Sinke,The Chemical Thermody-namics of Organic Compounds~Krieger, Malabar, FL, 1987!; see also the‘‘difference method,’’ N. Cohen and S. W. Benson, Chem. Rev.93, 2419~1993!.


4C. E. Blom and A. Bauder, Chem. Phys. Lett.82, 492 ~1981!.5C. E. Blom and A. Bauder, J. Am. Chem. Soc.104, 2993~1982!.6H. Hasegawa, O. Ohashi, and I. Yamaguchi, J. Mol. Struct.82, 205~1982!.

7M. D. Newton and G. A. Jeffrey, J. Am. Chem. Soc.99, 2413~1977!.8T.-K. Ha, C. E. Blom, and H. H. Gu¨nthard, J. Mol. Struct.; THEOCHEM85, 285 ~1981!.

9H. Hollenstein, T.-K. Ha, and H. H. Gu¨nthard, J. Mol. Struct.146, 289~1986!.

10M. Flock and M. Ramek, Int. J. Quant. Chem.26, 505 ~1992!.11P. D. Godfrey, F. M. Rodgers, and R. D. Brown, J. Am. Chem. Soc.119,

2232 ~1997!.12F. Jensen, Acta Chem. Scand.51, 439 ~1997!.13K. Iijima, M. Kato, and B. Beagley, J. Mol. Struct.295, 289 ~1993!.14H. Hollenstein, R. W. Scha¨r, N. Schwizgebel, G. Grassi, and H. H

Gunthard, Spectrochim. Acta A39, 193 ~1983!.



Dow

TABLE 4. Ideal gas thermodynamic properties of glycolic acid C2H4O3(g) at the standard state pressure,p°50.1 MPa~Tr5298.15 K)

T~K!

Cp°~J K21 mol21!

S°~J K21 mol21!

2(G°2H°(Tr))/T~J K21 mol21!


D fH°~kJ mol21!


0 0.000 0.000 ` 217.007 2567.940 2567.940 `25 37.880 194.730 839.900 216.129 2569.214 2566.334 1183.27450 39.654 221.605 524.756 215.158 2571.011 2562.818 587.96475 42.201 238.111 426.614 214.138 2572.893 2558.300 388.829

100 46.011 250.752 381.121 213.037 2574.448 2553.193 288.955

150 55.327 271.119 341.183 210.510 2577.040 2541.987 188.734180 61.435 281.742 330.402 28.759 2578.430 2534.844 155.206190 63.524 285.120 327.931 28.134 2578.873 2532.410 146.368200 65.636 288.431 325.873 27.488 2579.308 2529.953 138.408

210 67.769 291.685 324.168 26.821 2579.732 2527.475 131.200220 69.920 294.888 322.764 26.133 2580.147 2524.977 124.644230 72.089 298.043 321.621 25.423 2580.551 2522.460 118.653240 74.272 301.158 320.704 24.691 2580.945 2519.926 113.157250 76.467 304.234 319.983 23.937 2581.327 2517.376 108.098

260 78.669 307.276 319.436 23.162 2581.698 2514.811 103.425270 80.876 310.286 319.042 22.364 2582.057 2512.231 99.096280 83.082 313.267 318.782 21.544 2582.403 2509.639 95.073290 85.285 316.221 318.643 20.702 2582.737 2507.034 91.325

298.15 87.074 318.610 318.610 0.0002583.000 2504.902 88.456

300 87.480 319.150 318.611 0.161 2583.059 2504.418 87.826350 98.188 333.446 319.716 4.806 2584.470 2491.195 73.306400 108.146 347.217 322.298 9.968 2585.568 2477.792 62.392450 117.092 360.482 325.809 15.6032586.386 2464.267 53.890500 124.943 373.235 329.918 21.6582586.965 2450.666 47.080

600 137.622 397.192 339.162 34.8182587.557 2423.343 36.855700 147.128 419.154 349.044 49.0772587.601 2395.964 29.547800 154.453 439.298 359.085 64.1712587.259 2368.606 24.067900 160.307 457.840 369.041 79.9192586.638 2341.310 19.809

1000 165.136 474.988 378.789 96.1982585.808 2314.095 16.406

1100 169.214 490.923 388.267 112.9212584.815 2286.970 13.6271200 172.712 505.800 397.449 130.0222583.696 2259.942 11.3151300 175.742 519.747 406.326 147.4482582.482 2233.008 9.3621400 178.385 532.870 414.900 165.1572581.200 2206.174 7.6921500 180.703 545.258 423.182 183.1142579.868 2179.431 6.248

1600 182.744 556.987 431.181 201.2892578.508 2152.761 4.9871700 184.547 568.121 438.912 219.6552577.132 2126.198 3.8781800 186.144 578.716 446.387 238.1912575.750 299.707 2.8931900 187.564 588.818 453.620 256.8782574.375 273.299 2.0152000 188.830 598.472 460.623 275.6992573.016 246.960 1.226


nloaded 02 Jul 2012 to 129.6.105.191. Redistribution subject to AIP license or copyright; see http://jpcrd.aip.org/about/rights_and_permissions


6. Glyoxal, O BCHACHBO

Glyoxal (C2H2O2) Ideal gas Mr558.0366D fH°(0 K)52206.460.5 kJ mol21


Molecular constantstrans-Glyoxal cis-Glyoxal

Point group: C2h C2n

Symmetry number,s: 2 2Ground electronic state: X 1Ag X 1A1

Quantum weight,gx: 1 1

Relative energy,eX , cm21: 0 1555

Vibrational frequencies,n i , anddegeneracies,gi


n1 Ag 2843.27 1 A1 2841 1n2 1744.12 1 1746 1n3 1352.60 1 1369 1n4 1065.81 1 827 1n5 550.53 1 284.5 1n6 Au 801.36 1 A2 1050 1n7 . . . a 1 . . . a 1n8 Bg 1047.81 1 B1 750 1n9 Bu 2835.07 1 B2 2810 1n10 1732.10 1 1761 1n11 1312.38 1 1360 1n12 338.55 1 825 1

Geometry:

r ~C—C! 1.52560.003 Å 1.522 År ~CvO! 1.20760.002 Å 1.208 År ~C—H! 1.11660.008 Å 1.109 Å

/C—CvO 121.260.2° 123.1°/OvC—H 126.661.7° 122.8°

Rotational constants, cm21:A0 1.844 319 0.891 062B0 0.160 021 0.206 503C0 0.147 351 0.167 864

Product of moments of inertia,I AI BI C310117 g3 cm6:

504.42 710.17

Reduced moment of inertia for CHOtop, I r31039 g cm2:

0.8199 0.4807

Symmetry number for CHO top,sm : 1 1

aInstead of torsional moden7 ~126.7 cm21 for trans- and 89.6 cm21 for cis-glyoxal!, the contributions dueto the internal rotation were calculated from the potentialV(w)5 1

2(n516 Vn(12cosnw), where w is the

torsional angle,V151587.6,V251139.5,V35259.0,V452110.9,V5540.0, andV650.0 ~in cm21!. Forthe internal rotational constantB, the Fourier expansion coefficients were usedB5B01(n51

6 Bn cosnwwhereB054.213,B1521.117,B250.421,B3520.126,B450.040,B5520.015, andB650 ~in cm21!.



A

tio

otb

dohpeeree-tic-

onrm

diheo

gv

io

as

e

r-re

-sise

n-

-

eby

lbe-

l

the

efi-

xalec-

er

eyteso-



The value ofD fH° ~298.15 K! for glyoxal accepted in thiswork was determined by Fletcher and Pilcher1 from mea-surements of heat of combustion by flame calorimetry.lower value of 2224.3 kJ mol21 was obtained by Curtisset al.2 from ab initio calculation.


It has been shown both spectroscopically3–18 andtheoretically19–35that glyoxal (OvCH—CHvO) undergoesrotational isomerization and exists in two planar,trans andcis, forms. The structure of the more stabletrans conformerhas been determined by a combination of electron diffracand rotational data.36 As trans-glyoxal has no dipole mo-ment, there is no microwave spectrum, and accurate rtional constants for the ground state can only be obtainedrotational analysis of infrared or electronic absorption banThe values obtained for the rotational constantstrans-glyoxal4,5,13,14,37 are in good agreement with eacother. Using the rotational constants for the five isotopic scies, Birsset al.11 have evaluated the structural parametfor trans-glyoxal. These parameters are in excellent agrment with electron diffraction results.36 In general, these experimental geometries are in good agreement with theoreresults.24,26,28,33–35,38–43The product of the principal moments of inertia for the planar structure oftrans-glyoxal ofC2h symmetry was calculated here using the rotational cstants determined from a high-resolution Fourier-transfostudy of trans-glyoxal.15 Structural parameters oftrans-glyoxal given above are those obtained from an electronfraction investigation.36 These parameters reproduce tspectroscopic moments of inertia with in an accuracy0.2%–0.3%.

Rotational constants for the ground state ofcis-glyoxalwere obtained from rotational analysis of the 0–0 band6,8 andby microwave spectroscopy.7,10,12,17,18The product of theprincipal moments of inertia for the planar structure ofcis-glyoxal of C2n symmetry was calculated in this work usinthe rotational constants determined from microwastudies.17,18 Sets of possible structural parameters ofcis-glyoxal were evaluated using the rotational constants forisotopomers combined with assumptions of the valuessome parameters.7,8,10,28,44The geometry ofcis-glyoxal wasalso calculated byab initio22,24,26–29,31–33,35,38,39,41,42and mo-lecular mechanics43 methods. Structural parameters ofcis-glyoxal shown above were proposed by Tyulinet al.44 fromanalysis of microwave data.17

Vibrational spectra of glyoxal were studied in the gphase4–8,10,13,15,16,45–55 and with matrix isolationtechniques.56–58 The experimental assignments have beconfirmed by normal coordinate analyses44,59–64and theoret-ical calculations.26,28,29,31,34,35,40,43,65–70The adopted valuesfor vibrational frequencies oftrans-glyoxal were taken fromthe investigation of dispersed fluorescence spectra53 (n1

2n5 ,n8), high-resolution infrared spectra48

(n6 ,n7 ,n11,n12), a rotational fine structure of the C–H


n

a-y

s.f

-s-

al

-

f-

f

e

tsf

n

stretching band5 (n9) and a high-resolution infrared Fourietransform study15 (n10). The uncertainties in these values awithin 0.5 cm21. The adopted values ofn12n7 andn10 fun-damental frequencies ofcis-glyoxal are those observed fromgas and Ar-matrix spectra.13,18,55,58For unobserved frequencies (n8 ,n9 ,n11,n12), the values were selected on the baof ab initio calculations;28,31,35,68and their uncertainties arestimated to be 25–50 cm21.

The torsional potential function for glyoxal has been ivestigated experimentally3,6,7,9,13,16,18,71 andtheoretically19–34,70,72 by many authors. An early infraredstudy3 suggested a very hightrans-cisrotation barrier (Vrot)of 4810 cm21 based on a torsional frequency of 128 cm21.Currie and Ramsay6 provided the first estimate forcis-transenthalpy difference,DH5(11256100) cm21, from the tem-perature dependence ofcis andtransabsorption bands in thevisible spectrum. Duriget al.9 obtained the torsional potential function for glyoxal that fits the infrared data of thetransconformer and the microwave intensity data of thecis con-former and yields theDH5(11806150) cm21 with a barrierheightVrot51770 cm21. The energy difference between thcis and trans conformers has been revised upwards twiceButz et al., first to (13506200) cm21 derived from a spec-troscopic temperature study13 and then to (16886100) cm21

by fitting spectroscopic data to a torsional potential.16 Thepotential function obtained by Butzet al.16 has a barrier totrans-cis rotation of 2077 cm21. Recently Hu¨bner et al.18

have determined thecis-trans enthalpy difference,DH5(1555648) cm21, from absorption intensities of glyoxaby microwave spectroscopy. This value is intermediatetween the values reported by Butzet al.13,16 Based on thisvalue forDH, Hubneret al.18 have recalculated the potentiacurve for internal rotation in glyoxal (Vrot52003 cm21). Nu-merousab initio calculations yield different results forDHdepending on the basis sets and levels of calculation~1050,20

1320–1970,34 1490,29 1500–1990,31 1504,72 ;1600,26,27,32

1700–2200,23 ;2000,22,24,25,28,30and 2422 cm21!.70 Due tothis wide range they are not of help in deciding amongavailable experimental data.

The torsional potential function determined by Hu¨bneret al.18 is accepted in this work in order to account for thinternal rotation in glyoxal. The Fourier expansion coefcients for the internal rotation constantB were adopted to bethe same as those used by Duriget al.9 and later by otherauthors.16,18The values of the reduced moment of inertia,I r ,were calculated from accepted structural parameters~seeabove!.

Experimentally observed absorption spectra of glyohave been identified with transitions to the excited eltronic states a 3Au (T0519 199 cm21) and A 1Au (T0

521 973 cm21).45,73,74 These assignments agree with othexperimental75–79 and theoretical35,80,81studies. Dykstra andSchaefer82 have predicted two low-lying~;15 000 cm21!unobserved triplet states fromab initio calculation. Becauseof high energies of excited electronic states of glyoxal, thare not considered in this work. These electronic stawould only make an appreciable contribution to the therm




J. Phys. Chem. Ref

Dow

TABLE 5. Ideal gas thermodynamic properties of glyoxal C2H2O2(g) at the standard state pressure,p°50.1 MPa~Tr5298.15 K)

T~K!

Cp°~J K21 mol21!

S°~J K21 mol21!

2(G°2H°(Tr))/T~J K21 mol21!


D fH°~kJ mol21!


0 0.000 0.000 ` 213.690 2206.432 2206.432 `

25 33.558 168.135 682.424 212.857 2206.857 2206.353 431.14650 36.353 192.179 431.899 211.986 2207.559 2205.605 214.79175 39.053 207.448 354.677 211.042 2208.268 2204.466 142.401

100 41.428 219.011 319.370 210.306 2208.805 2203.114 106.095

150 45.964 236.671 289.008 27.851 2209.665 2200.077 69.672180 48.675 245.290 281.018 26.431 2210.146 2198.114 57.490190 49.594 247.947 279.209 25.940 2210.306 2197.441 54.280200 50.525 250.514 277.710 25.439 2210.467 2196.761 51.388

210 51.471 253.002 276.474 24.929 2210.627 2196.071 48.769220 52.433 255.419 275.463 24.410 2210.788 2195.374 46.387230 53.414 257.771 274.643 23.880 2210.948 2194.670 44.210240 54.414 260.066 273.987 23.341 2211.107 2193.959 42.213250 55.434 262.307 273.476 22.792 2211.265 2193.241 40.375

260 56.473 264.502 273.089 22.233 2211.422 2192.517 38.677270 57.533 266.653 272.810 21.663 2211.576 2191.787 37.103280 58.611 268.765 272.628 21.082 2211.729 2191.051 35.641290 59.707 270.841 272.531 20.490 2211.880 2190.310 34.278

298.15 60.612 272.508 272.508 0.0002212.000 2189.702 33.235

300 60.819 272.883 272.509 0.112 2212.027 2189.563 33.005350 66.557 282.686 273.270 3.296 2212.711 2185.765 27.723400 72.398 291.956 275.031 6.770 2213.294 2181.874 23.750450 78.086 300.814 277.407 10.533 2213.765 2177.917 20.652500 83.427 309.321 280.176 14.572 2214.126 2173.913 18.168

600 92.680 325.380 286.389 23.395 2214.547 2165.827 14.436700 99.929 340.236 293.034 33.041 2214.638 2157.696 11.767800 105.446 353.957 299.803 43.323 2214.488 2149.568 9.766900 109.622 366.629 306.534 54.086 2214.174 2141.471 8.211

1000 112.807 378.351 313.137 65.2142213.761 2133.416 6.969

1100 115.270 389.223 319.566 76.6232213.288 2125.404 5.9551200 117.204 399.339 325.797 88.2512212.789 2117.436 5.1121300 118.749 408.784 331.821 100.0512212.289 2109.508 4.4001400 120.001 417.631 337.638 111.9912211.806 2101.621 3.7911500 121.030 425.947 343.251 124.0442211.349 293.765 3.265

1600 121.887 433.786 348.667 136.1912210.932 285.921 2.8051700 122.609 441.198 353.894 148.4172210.556 278.122 2.4001800 123.223 448.224 358.941 160.7092210.227 270.337 2.0411900 123.749 454.900 363.817 173.0582209.948 262.575 1.7202000 124.204 461.260 368.531 185.4572209.719 254.823 1.432

nc

my

en

nin-

r.fm-r-

-

ep-jan

dynamic functions at temperatures above 3000 K.The uncertainties in the calculated thermodynamic fu

tions ~Table 5! are estimated to be~0.5–3.0! J K21 mol21 forCp°(T) and ~1.0–3.0! J K21 mol21 for S°(T).

The thermodynamic functions of glyoxal as an equilibriumixture of trans and cis conformers were calculated bCompton.83 The discrepancies betweenCp°(T) and S°(T)values calculated in this work and in Compton83 increasewith temperature and reach 3.1 and 2.2 J K21 mol21, respec-tively, at 1000 K. These discrepancies are due to differ

. Data, Vol. 30, No. 2, 2001


-

t

molecular constants used in the calculations and the noclusion of internal rotation in glyoxal by Compton.83 Valuesof H°(T)2H°(0) given by Compton appear to be in erroHollensteinet al.84 derived the thermodynamic functions oglyoxal using the semiclassical approximation for the suover-states calculation for nonrigid molecules. The diffeence between theirCp°(T) andS°(T) values and those calculated in this work range from 0.1 to 8.8 J K21 mol21

depending on the level of approximation used. The discrancies with the results of statistical calculations by Natara


em

-

-an

nn.

.

,

C

R

hy

ys

l.

Am

t.

an

.

er-

em.

m.

.

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et al.85 amount to~50–60! J K21 mol21 and cannot be due todifferences in the molecular constants used.

6.3. References

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5A. R. H. Cole and G. A. Osborne, J. Mol. Spectrosc.36, 376 ~1970!.6G. N. Currie and D. A. Ramsay, Can. J. Phys.49, 317 ~1971!.7J. R. Durig, C. C. Tong, and Y. S. Li, J. Chem. Phys.57, 4425~1972!.8D. A. Ramsay and C. Zauli, Acta Phys. Acad. Sci. Hung.35, 79 ~1974!.9J. R. Durig, W. E. Bucy, and A. R. H. Cole, Can. J. Phys.53, 1832~1975!.

10A. R. H. Cole, Y. S. Li, and J. R. Durig, J. Mol. Spectrosc.61, 346~1976!.11F. W. Birss, D. B. Braund, A. R. H. Cole, R. Engleman, Jr., A. A. Gree

S. M. Japar, R. Nanes, B. J. Orr, D. A. Ramsay, and J. Szyszka, CaPhys.55, 390 ~1977!.

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Spectrosc.184, 221 ~1997!.19U. Pincelli, B. Cadioli, and D. J. David, J. Mol. Struct.9, 173 ~1971!.20T. K. Ha, J. Mol. Struct.12, 171 ~1972!.21K. R. Sundberg and L. M. Cheung, Chem. Phys. Lett.29, 93 ~1974!.22C. E. Dykstra and H. F. Shaefer III, J. Am. Chem. Soc.97, 7210~1975!.23P. N. Skancke and S. Saebø, J. Mol. Struct.28, 279 ~1975!.24Y. Osamura and H. F. Shaefer III, J. Chem. Phys.74, 4576~1981!.25G. R. De Mare, J. Mol. Struct: THEOCHEM107, 127 ~1984!.26T. J. Kakumoto, Sci. Hiroshima Univ. A51, 69 ~1987!.27S. Saebo”, Chem. Phys.113, 383 ~1987!.28C. W. Bock, Y. N. Panchenko, and S. V. Krasnoshchiokov, Chem. P

125, 63 ~1988!.29G. E. Scuseria and H. F. Schaefer III, J. Am. Chem. Soc.111, 7761

~1989!.30C. W. Bock and A. Toro-Labbe, J. Mol. Struct: THEOCHEM232, 239

~1991!.31G. R. De Mare, J. Mol. Struct: THEOCHEM253, 199 ~1992!.32G. R. De Mare, Yu. N. Panchenko, and A. V. Abramenkov, J. Ph

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Struct: THEOCHEM393, 39 ~1997!.35J. F. Stanton and J. Gauss, Spectrochim. Acta A53, 1153~1997!.36K. Kuchitsu, T. Fukuyama, and Y. Morino, J. Mol. Struct.1, 463 ~1968!.37J. Paldus and D. A. Ramsay, Can. J. Phys.45, 1389~1967!.38C. W. Bock, P. George, C. J. Mains, and M. Trachtman, J. Mol. Struct.49,

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Spectrosc.17, 177 ~1986!.51G. A. Bickel and K. K. Innes, J. Chem. Phys.86, 1752~1987!.52D. Frye, L. Dai, and H.-L. Lapierre, J. Chem. Phys.89, 2609~1988!.53E. Pebay Peyroula, A. Delon, and R. Jost, J. Mol. Spectrosc.132, 123

~1988!.54W. G. Wickun and K. K. Innes, J. Mol. Spectrosc.127, 277 ~1988!.55R. Y. Dong, R. Nanes, and D. A. Ramsay, Can. J. Chem.71, 1595~1993!.56M. Diem, B. G. MacDonald, and E. K. C. Lee, J. Phys. Chem.85, 2227

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17544~1995!.69X. Zhou, C. J. M. Wheeless, and R. Liu, Vib. Spectrosc.12, 53 ~1996!.70M. L. Senent, J. Mol. Struct.406, 51 ~1997!.71H. H. Le and V. I. Tyulin, Zh. Strukt. Khim.16, 63 ~1975!.72E. L. Coitino and J. Tomasi, Chem. Phys.204, 391 ~1996!.73G. W. King, J. Chem. Soc. 5054~1957!.74D. A. Ramsay, M. Verloet, F. Vanhorenbeke, M. Godefroid, and M. H

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~1973!.78J. Kelder, H. Cerfontain, J. K. Eweg, and R. P. H. Rettschnick, Che

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2422 ~1977!.81W. B. Mueller, J. F. Harrison, and P. J. Wagner, J. Am. Chem. Soc.100,

33 ~1978!.82C. E. Dykstra and H. F. Schaefer III, J. Am. Chem. Soc.98, 401 ~1976!.83D. A. C. Compton, J. Chem. Soc., Perkin Trans. 2, 1307~1977!.84H. Hollenstein, A. Bauder, and H. H. Gu¨nthard, Chem. Phys.47, 269

~1980!.85A. Natarajan, P. Kolandaivelu, and A. Savarianandam, J. Indian Ch

Soc.59, 1155~1982!.




7. Cyanooxomethyl Radical, OC ˙ CN

Cyanooxomethyl radical (C2NO) Ideal gas Mr554.0281D fH° (0 K)5207.2610.0 kJ mol21

S°(298.15K)5278.261.5 J K21mol21 D fH° (298.15 K)5210.0610.0 kJ mol21

Molecular Constants

Point group:Cs Symmetry number:s51Ground electronic state:X 2A8 Energy:eX50 cm21 Quantum weight:gX52

Excited electronic state:A 2A9 Energy:eA515 500 cm21 Quantum weight:gA52

Vibrational frequencies,n i , and degeneracies,gi


A8 n1 2249 1 n4 488n2 1703 1 n5 174 1n3 909 1 A9 n6 233 1

Geometry

r (CvO)51.1960.02 År (C—C)51.4760.02 År (wN)51.1660.02 Å/OvC—C512863°/C—CwN517065°


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isforthe


No experimental data are available for enthalpy of formtion of the cyanooxomethyl radical. The value acceptedthis work was estimated by Francisco and Liu1 by using theisodesmic reaction approach with the following reaction:

OCCN1HCN→C2N21HCO.

The relationship between the enthalpy of formationOCCN and the enthalpy change of the above reaction is

D fH°~OCCN!5D fH°~C2N2!1D fH°~HCO!

2D fH°~HCN!2D rH°.

Based on known experimental enthalpies of formationHCN, C2N2, HCO, and theD rH° value predicted byab ini-tio calculations, Francisco and Liu1 have estimated the enthalpy of formation for OC˙ CN to be 207.5–210.0 kJ mol21.


There are no experimental data on structure and vibtional spectra of OC˙ CN. According to ab initiocalculations,1,2 a bent structure ofCs symmetry is adopted inthis work for OCCN in the ground electronic stateX 2A8.The product of the principal moments of inertia was calclated using the structural parameters shown above. Th



-n

f

f

a-

-se

values are based on the results ofab initio calculations1,2 andcomparison with structural parameters of CO~CN!2, COX2,and XCO (X5F, Cl) molecules.

Vibrational frequencies of OC˙ CN were calculated in thiswork using the following force constants:

f CvO511.413 mdyn/Å, f C—CwN50.110 mdyn Å,

f C—C57.225 mdyn/Å, f CC,CO50.513 mdyn/Å,

f CwN513.674 mdyn/Å, f CC,CN521.543 mdyn/Å,

f C—CvO50.750 mdyn Å, f CC,CCO50.585 mdyn.

These constants were transferred from the CO~CN!2 mol-ecule except forf C—C5O and f C—C[N whose values werereduced by comparison with the bending force constantCOX2 and XCO (X5F, Cl, Br). Normal coordinate analysifor CO~CN!2 was carried using the vibrational assignmentMiller et al.3 The uncertainties in the calculated frequencof OCCN can reach 50 cm21. These frequencies agree oveall with those resulting from theab initio calculation.1

The first excited electronic stateA 2A9 of OCCN was pre-dicted at an energy of;15 500 cm21 by an ab initiocalculation1 and was included in the calculations in thwork. Structural parameters and vibrational frequenciesthe A 2A9 state were accepted as identical to those ofground state.


nc

m


The uncertainties in the calculated thermodynamic futions ~Table 6! are estimated to be~1.5–2.0! J K21 mol21 forCp°(T) and ~1.5–3.0! J K21 mol21 for S°(T).

Ideal gas thermodynamic properties of the cyanooxoethyl radical have not been reported previously.


-

-

7.3. References

1J. S. Francisco and R. Liu, J. Chem. Phys.107, 3840~1997!.2A. L. Cooksy, J. Am. Chem. Soc.117, 1098~1995!.3F. A. Miller, B. M. Harney, and J. Tyrrell, Spectrochim. Acta A27, 1003~1971!.

TABLE 6. Ideal gas thermodynamic properties of the cyanooxomethyl radical C2NO~g! at the standard state pressure,p°50.1 MPa (Tr5298.15 K)

T~K!

Cp°~J K21 mol21!

S°~J K21 mol21!

2(G°2H°(Tr))/T~J K21 mol21!


D fH°~kJ mol21!


0 0.000 0.000 ` 213.594 207.190 207.190 `25 33.297 174.512 685.016 212.763 207.298 206.094 2430.60450 35.132 197.975 436.251 211.914 207.405 204.851 2214.00375 38.803 212.901 359.439 210.990 207.563 203.542 2141.757

100 42.195 224.543 324.309 29.977 207.781 202.171 2105.602

150 47.280 242.677 294.223 27.732 208.327 199.251 269.384180 49.604 251.509 286.384 26.278 208.683 197.403 257.284190 50.296 254.210 284.620 25.778 208.802 196.773 254.096200 50.955 256.807 283.165 25.272 208.921 196.137 251.225

210 51.582 259.308 281.970 24.759 209.039 195.495 248.626220 52.182 261.721 280.995 24.240 209.156 194.847 246.262230 52.757 264.054 280.208 23.715 209.271 194.194 244.102240 53.309 266.311 279.582 23.185 209.384 193.536 242.121250 53.839 268.498 279.095 22.649 209.496 192.873 240.298

260 54.350 270.620 278.729 22.108 209.605 192.206 238.614270 54.842 272.680 278.467 21.562 209.712 191.535 237.054280 55.318 274.683 278.296 21.012 209.817 190.860 235.605290 55.779 276.632 278.205 20.456 209.919 190.181 234.255

298.15 56.145 278.183 278.183 0.000 210.000 189.625 233.221

300 56.226 278.531 278.184 0.104 210.018 189.499 232.994350 58.286 287.356 278.877 2.968 210.473 186.041 227.765400 60.126 295.262 280.439 5.929 210.852 182.524 223.835450 61.811 302.442 282.491 8.978 211.153 178.965 220.773500 63.373 309.036 284.820 12.108 211.379 175.376 218.321

600 66.186 320.845 289.863 18.589 211.634 168.146 214.638700 68.609 331.235 295.046 25.332 211.683 160.892 212.006800 70.666 340.534 300.161 32.299 211.585 153.643 210.032900 72.395 348.960 305.122 39.454 211.379 146.410 28.497

1000 73.839 356.665 309.897 46.768 211.093 139.204 27.271

1100 75.044 363.761 314.475 54.214 210.748 132.033 26.2701200 76.051 370.335 318.860 61.770 210.353 124.893 25.4361300 76.896 376.457 323.057 69.419 209.918 117.792 24.7331400 77.609 382.182 327.078 77.145 209.441 110.720 24.1311500 78.214 387.558 330.933 84.937 208.931 103.689 23.611

1600 78.731 392.622 334.632 92.785 208.384 96.710 23.1571700 79.175 397.409 338.185 100.681 207.808 89.746 22.7581800 79.559 401.946 341.602 108.618 207.199 82.823 22.4031900 79.894 406.257 344.893 116.591 206.559 75.929 22.0872000 80.189 410.362 348.064 124.596 205.890 69.071 21.804




8. Oxalic Acid, HO ACOACOAOH

Oxalic acid (C2H2O4) Ideal gas Mr590.0354D fH°(0 K)52721.262.0 kJ mol21


Molecular constantsPoint group:C2h Symmetry number:s52Ground electronic state:X 1Ag

Energy:eX50 cm21 Quantum weight:gX51



Ag n1 3484 1 n10 –a 1n2 1800 1 Bg n11 851 1n3 1423 1 n12 563 1n4 1195 1 Bu n13 3484 1n5 815 1 n14 1826 1n6 608 1 n15 1278 1n7 405 1 n16 1127 1

Au n8 666 1 n17 651 1n9 460 1 n18 264 1

aInstead of torsional moden10;90 cm21, the contributions due to theinternal rotation about C–C bond were calculated from the potentialV(w)5 1

2V1(12cosw), where w is the torsional angle andV1

5700 cm21.

COOH top: Reduced moment of inertia,I r53.6454310239 g cm2, Symmetry number,sm51

Geometryr ~C—C!51.54860.004 År ~CvO!51.20860.001 År ~C—O!51.33960.002 År ~O—H!51.05660.014 Å/C—CvO5123.160.9°/OvC—O5125.060.2°/C—O—H5104.462.3°


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Wilhoit and Shiao1 have measured the enthalpy of combustion of solid oxalic acid in a rotating platinum bomb carimeter and have calculated D fH°~C2H2O4,cr,298.15 K!52~829.961.0) kJ mol21. The enthalpy of for-mation of gaseous oxalic acid is calculated from this vaby adding the enthalpy of sublimation,DsubH°598.1kJ mol21, obtained from vapor pressure measurements.2


Nahlovskaet al.3 carried out an electron diffraction and aIR study of oxalic acid indicating that the structure was inplanar trans conformation ~C2h symmetry! in which the



e

hydrogen atom of one COOH group participated in intramlecular hydrogen bonding with the carbonyl oxygen of tother COOH group~‘‘hydrogen bonded’’trans conformer!.Infrared matrix-isolation spectra of oxalic acid4 were inter-preted in terms of the same model and the tentative consion was made that a second conformer of oxalic acid exin the vapor phase. This conformer was suggested to btrans form ~C2h symmetry! with the hydrogen atom of eacCOOH group oriented towards the carbonyl oxygen ofsame COOH group~‘‘free’’ trans form!. Oxalic acid wasdetermined to be in itstrans conformation from x-ray crys-tallographic studies5 and no other conformers were observeStudies of oxalic acid in solution6 favored almost free rota


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tion, which would include a range of possible conformatioAb initio studies of oxalic acid7–9 have obtained a mosstable hydrogen bondedtrans planar structure in agreemenwith the results of an electron diffraction investigation.3 Thehydrogen bonded or freetrans form was found to be lowesenergy depending on the basis set used in theab initiocalculations.10 The freetrans conformer was reported to bmost stable by an earlierab initio study.11

The hydrogen bondedtrans form ~C2h symmetry! is ac-cepted for oxalic acid in this work. Its product of principmoments of inertia was calculated using the structuralrameters determined from the electron diffraction stud3

Following the results of a theoretical calculation by Tyrrel9

it was assumed that there is a slight energy preferencethis conformer and only a small barrier of about 2 kcal mo21

~700 cm21! separating it from other stable conformers. Tsimple approximate potential,

V~w!5 12V1~12cosw!,

wherew is the OC—CO torsional angle, was used here fthe calculation of internal rotational contributions to the thmodynamic functions of oxalic acid. The value of the rduced moment of inertia for the COOH top was derived frothe molecular constants shown above.

There are several studies of the vibrational spectra offree C2H2O4 molecule3,4,12–14but some fundamentals are stunobserved. Stace and Oralratmanee14 have reported the infrared vapor phase measurements and the first vapor pRaman spectra. They have proposed a new vibrationalquencies assignment based on their experimental resulwell as calculated in-plane frequencies using an UreBradley force field derived from formic and acetic acid. Reington and Redington4 have investigated the infrared spectof oxalic acid vapor and the infrared spectra of matrisolated C2H2O4, C2HDO4, and C2D2O4 and have carried oua normal coordinate analysis using a general valence ffield for the in-plane infrared-active modes. None of tabove studies, however, gives a complete vibrational assment for oxalic acid. De Villepin and Novak15 have devel-oped a general valence force field for both infrared andman frequencies using the relatively small numberexperimentally observed fundamentals. Their force fieldproduces the experimental vibrational spectra of oxalicis comparable with force fields already known for other cboxylic acids. The fundamental frequenciesn22n5 and n7

adopted here were observed in the Raman spectra of gasoxalic acid.14 The 405 cm21 mode was subsequently reasigned ton7 .4 The values ofn8 , n9 , n132n16, andn18 arethose determined from gas-phase infrared spectra.4 The valuefor n17 was obtained from spectra of neon matrix-isolatoxalic acid.4 The uncertainties in these experimental frequcies are in the range of 5–10 cm21.

Redington and Redington4 have suggested tentative valufor n6(Ag)5538 cm21, n11(Bg)5590 cm21, and n12(Bg)5512 cm21 fundamentals using possible combination ban


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-

.

The adopted values of these frequencies were taken fnormal coordinate calculations.15 Calculations for the otherfrequencies are in good agreement with experimental resThe value of the symmetric O—H stretching frequencyn1

was accepted to be the same as the value of antisymmO—H stretching (n13) and it coincides with the calculatevalue.15 The uncertainties in these frequencies are estimato be 25–50 cm21.

Evidently due to its weak intensity, the C—C torsionmode n10(Au) was not observed in a vapor phase specsearch that extended down to 35 cm21.4 Ab initiocalculations8,10 have suggested the value of 160 cm21 for thetorsional mode, however, it should be noted that all otcalculated values are much greater than those from expment. Cyvin and Alfheim16 have calculatedn10590 cm21

using force constants transferred from formic and aceticids. The value of 110 cm21 was obtained from other normacoordinate calculation.15 The corresponding torsional modfor oxalyl fluoride ~F—CO—CO—F! was observed in thegas phase at 54 cm21 and in the solid phase at 94 cm21.17

From the ratio of n tors~C2F2O2, solid!/ntors~C2F2O2, gas)51.74 and the value of 138 cm21 for the torsional mode ofsolid oxalic acid,15,18the value of;80 cm21 for the torsionalmode of gaseous oxalic acid is expected.

The uncertainties in the calculated thermodynamic futions ~Table 7! may be as much as~5–7! J K21 mol21 forCp°(T) and~5–10! J K21 mol21 for S°(T). These uncertain-ties arise from the uncertainties in the adopted values ofvibrational frequencies and the simple and approximmodel for internal rotation.

Ideal gas thermodynamic properties of oxalic achave not been reported previously.

8.3. References

1R. C. Wilhoit and D. Shiao, J. Chem. Eng. Data9, 595 ~1964!.2R. S. Bradley and S. Cotson, J. Chem. Soc. 1684~1953!.3Z. Nahlovska, B. Nahlovsky, and T. G. Strand, Acta Chem. Scand.24,2617 ~1970!.

4R. L. Redington and T. E. Redington, J. Mol. Struct.48, 165 ~1978!.5J. L. Derissen and P. H. Smit, Acta Crystallogr. Sect. B: Struct. CrystolCryst. Chem.30, 2240~1974!.

6T. A. Shippey, J. Mol. Struct.65, 71 ~1980!.7C. Van Alsenoy, V. J. Klimkowski, and L. Scha¨fer, J. Mol. Struct:THEOCHEM 109, 321 ~1984!.

8T. Kakumoto, J. Sci. Hiroshima Univ. A51, 69 ~1987!.9J. Tyrrell, J. Mol. Struct: THEOCHEM258, 389 ~1992!.

10T. Kakumoto, K. Saito, and A. Imamura, J. Phys. Chem.91, 2366~1987!.11D. Ajo, G. Condorelli, I. Fragala, and G. Granozzi, J. Mol. Struct.37, 160

~1977!.12M. Pava Bruce and F. E. Stafford, J. Phys. Chem.72, 4628~1968!.13L. Bardet, G. Fleury, and V. Tabacik, C. R. Acad. Sci. B270, 1277

~1970!.14B. C. Stace and C. Oralratmanee, J. Mol. Struct.18, 339 ~1973!.15J. De Villepin, A. Novak, and D. Bougeard, Chem. Phys.73, 291 ~1982!.16S. J. Cyvin and I. Alfheim, Acta Chem. Scand.24, 2648~1970!.17J. R. Durig, S. C. Brown, and S. E. Hannum, J. Chem. Phys.54, 4428

~1971!.18J. De Villepin, A. Novak, and F. Romain, Spectrochim. Acta A34, 1009

~1978!.




9. Methyl Hydroperoxide, CH 3AOAOAH

Methyl hydroperoxide (CH4O2) Ideal gas Mr548.0414D fH°(0 K)52126.265.0 kJ mol21


Molecular constantsPoint group:C1 Symmetry number:s51 Number of optical isomers:n52Ground electronic state:X 1A Energy:eX50 cm21 Quantum weight:gX51



A n1 3604 1 n9 1145 1n2 2957 1 n10 1115 1n3 2955 1 n11 1003 1

TABLE 7. Ideal gas thermodynamic properties of oxalic acid C2H2O4~g! at the standard state pressure,p°50.1 MPa (Tr5298.15 K)

T~K!

Cp°~J K21 mol21!

S°~J K21 mol21!

2(G°2H°(Tr))/T~J K21 mol21!


D fH°~kJ mol21!


0 0.000 0.000 ` 217.321 2721.180 2721.180 `25 40.556 193.337 848.905 216.389 2722.227 2719.030 1502.31150 41.771 221.869 529.039 215.359 2723.498 2715.371 747.33375 43.565 239.102 429.695 214.295 2724.813 2711.016 495.189

100 46.685 252.031 383.721 213.169 2725.959 2706.240 368.897

150 56.008 272.618 343.382 210.615 2727.905 2695.943 242.346180 62.509 283.401 332.497 28.837 2728.902 2689.455 200.072190 64.693 286.839 330.004 28.201 2729.209 2687.255 188.937200 66.861 290.213 327.931 27.544 2729.504 2685.040 178.912

210 69.005 293.527 326.214 26.864 2729.786 2682.809 169.837220 71.116 296.786 324.802 26.164 2730.057 2680.566 161.585230 73.190 299.993 323.654 25.442 2730.316 2678.311 154.047240 75.223 303.151 322.734 24.700 2730.564 2676.044 147.135250 77.213 306.262 322.013 23.938 2730.801 2673.768 140.774

260 79.160 309.329 321.466 23.156 2731.027 2671.482 134.901270 81.061 312.352 321.073 22.355 2731.243 2669.187 129.460280 82.918 315.334 320.815 21.535 2731.450 2666.886 124.407290 84.731 318.275 320.677 20.696 2731.646 2664.576 119.701

298.15 86.176 320.644 320.644 0.0002731.800 2662.689 116.099

300 86.501 321.178 320.645 0.160 2731.834 2662.260 115.308350 94.724 335.142 321.729 4.695 2732.644 2650.598 97.095400 101.995 348.276 324.235 9.616 2733.273 2638.832 83.422450 108.424 360.668 327.601 14.8802733.761 2626.996 72.779500 114.112 372.392 331.499 20.4462734.137 2615.113 64.260

600 123.628 394.073 340.152 32.3522734.633 2591.258 51.473700 131.195 413.720 349.281 45.1072734.871 2567.341 42.335800 137.323 431.652 358.473 58.5432734.902 2543.401 35.480900 142.375 448.127 367.531 72.5362734.765 2519.472 30.149

1000 146.605 463.353 376.362 86.9912734.487 2495.566 25.885

1100 150.187 477.499 384.921 101.8362734.087 2471.692 22.3981200 153.247 490.701 393.192 117.0112733.590 2447.859 19.4951300 155.880 503.074 401.173 132.4712733.013 2424.068 17.0391400 158.158 514.711 408.872 148.1752732.379 2400.327 14.9361500 160.137 525.692 416.297 164.0922731.700 2376.632 13.115

1600 161.866 536.084 423.462 180.1952730.994 2352.965 11.5231700 163.381 545.943 430.379 196.4582730.273 2329.363 10.1201800 164.714 555.320 437.062 212.8652729.544 2305.796 8.8741900 165.891 564.258 443.523 229.3962728.823 2282.276 7.7602000 166.934 572.794 449.775 246.0382728.113 2258.789 6.759




n4 2861 1 n12 800 1n5 1509 1 n13 415 1n6 1453 1 n14 ¯

a 1n7 1450 1 n15 ¯

b 1n8 1348 1

aInstead of torsional moden145240 cm21, the contributions due to theinternal rotation of CH3 group around the C—O bond were calculatedfrom the potentialV(w)5 1

2V3(12cos3w), wherew is the H—C—O—Otorsional angle andV351120 cm21.bInstead of torsional moden155149 cm21, the contributions due to theinternal rotation of OH group around the O-O bond were calculated fromthe potential:V(w)5V01V1 cosw1V2 cos2w1V3 cos3w, wherew is theC—O—O—H torsional angle,V05780.7,V151111.1,V25555.6, andV3552.6 ~in cm21!.

CH3 top: Reduced moment of inertia,I r50.4282310239 g cm2, Symmetry number,sm53.

OH top: Reduced moment of inertia,I r50.138310239 g cm2, Symmetry number,sm51.

Geometryr ~C—H!51.09060.010 År ~O—H!50.97060.005 Å/C—O—O5105.360.5 Å/O—O—H5100.062.0°/H—C—O5109.564.0°w~C—O—O—H!512065°r ~C—O!51.42060.005 År ~O—O!51.46060.010 Å


Product of moments of inertia:I AI BI C5144.33102117 g3 cm6.

ailf

de

nt

e-

i-


Experimental data on enthalpy of formation are not avable for methyl hydroperoxide. Values oD fH°~CH3OOH,g,298.15 K! between 2122 and 2138kJ mol21 were estimated from semiempirical,1–3 molecularmechanics,4–6 ab initio,7 and group additivity8–10 calcula-tions. Lay et al.11 have estimatedD fH° ~298.15 K! to be(139.765.0) kJ mol21 using the experimentally determinevalue ofD fH°(CH3OO) with an average bond energy for thO–H bond in ROOH compounds. Based on the experimevalues ofD fH°(CH3O), D fH°(OH),12 and the bond energyof the O–O bond in CH3OOH,13 the value of2134.3 kJmol21 may be obtained for the enthalpy of formation of mthyl hydroperoxide. Benassiet al.5 proposed D fH°(298.15 K)52138.1 kJ mol21 by employing theoretical andempirical approaches. Similar values ofD fH° are predictedby the method of group equations from


-

al

D fH°~CH3OOH!

5D fH°~CH3OOCH3!1D fH°~CH3OH!

2D fH°~CH3OCH3!

5~2125.5!1~2201.5!2~2184.1!

52142.9 kJ mol21,

D fH°~CH3OOH!

5D fH°~CH3CH2OOH!1D fH°~CH3OH!

2D fH°~CH3CH2OH!

5~2173.6!1~2201.5!2~2235.2!

52139.9 kJ mol21,

~the D fH° values were taken from Pedley14 ~CH3OH,CH3OCH3, and CH3CH2OH!, Bakeret al.15 (CH3OOCH3),and Layet al.11 (CH3CH2OOH). The average of these est



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mates,213965.0 kJ mol21, is accepted in this work for theenthalpy of formation of methyl hydroperoxide at 298.15


The microwave spectrum of methyl hydroperoxidCH3OOH, has been investigated by Tyblewskiet al.16 How-ever, the assignment of the spectrum was complicatedcause of the widespread effects of the internal rotataround the O—O bond. The experimental results providdefinitive evidence that the minimum of the potential enerelative to internal rotation around the O—O bond corre-sponds to askewconformation. The adjustment to the oserved data resulted in a smalltrans barrier of 172.5 cm21.This barrier separates two equivalent potential minima asciated with two enantiomericskew forms. From a prelimi-nary interpretation of microwave data, Tyblewskiet al.17 re-ported almost all the structural parameters of the CH3OOHmolecule. In a more detailed study, Tyblewskiet al.16 gaveonly one parameter adjusted to the observed d/C—C—O5105.3°. All other structural parameters weadopted by those authors fromab initio calculations. Confor-mational properties of methyl hydroperoxide have beenvestigated theoretically.1,2,4–6,11,16,18–22Ab initio5,16,19–22andmolecular mechanics4,6 calculations provide an equilibriummolecular structure andtransbarrier in close agreement witthe conclusions of experimental study of Tyblewskiet al.16

The product of the principal moments of inertia of methhydroperoxide was calculated in this work using the rotional constants determined from a microwave study16

Structural parameters for theskew C1 symmetry conforma-tion given above are based on the experimental16 andtheoretical4–6,16,19–22data for CH3OOH and from comparisonwith the structural parameters of CH3OOCH3.

23 These pa-rameters give values for the rotational constants which diby only 0.4%–0.6% from the observed values.

Methyl hydroperoxide contains OH and CH3 groups,which rotate around O—O and C—O bonds. Contributionsto the thermodynamic functions from these hindered rotwere evaluated in this work based on available data on rtional barriers in CH3OOH. The value ofV351120 cm21

was accepted for the barrier to internal rotation of the metgroup around the C—O bond. This value was found from thmicrowave study16 and agrees closely with values obtainfrom ab initio calculations.4,16 The double-minimum potential energy function,

V~w!5V01V1 cosw1V2 cos 2w1V3 cos 3w,

was used in this work for the O—O internal rotation. Thisfunction was chosen earlier for the hindered rotation pottial function in hydrogen peroxide.24 The expansion coeffi-cientsV0 , V1 , V2 , andV3 can be expressed in terms of thtrans barrier heightVtrans , the cis barrier heightVcis , andthe COOH dihedral anglewe corresponding to a minimum othe potential function.24 The values ofV0 , V1 , V2 , andV3

were calculated in this work assumingVtrans5172.5 cm21,Vcis52500 cm21, and we5120°. The value of Vtrans



.

,

e-n

y

o-

a,

-

l-

r

sa-

l

-

5172.5 cm21(/C—O—O—H5180°) was taken from themicrowave study.16 It should be noted that substantiallower values ofVtrans from 80 to 126 cm21 were predictedby ab initio5,16,19,20and molecular mechanics6 calculations,whereas highVtrans values of 240–590 cm21 were foundfrom other molecular mechanics studies.4,5 No experimentaldata for theVcis rotational barrier have been published. Ivalue accepted in this work is based on theoretiresults4–6,16,25which agree closely with each other. The equlibrium COOH dihedral angle,we5120°, was estimated inthis work ~see above!. The values of the reduced momentsinertia for CH3 and OH tops were calculated from structurparameters given above.

Experimental data on the vibrational spectra of methyl hdroperoxide are unknown. Vibrational frequenciesCH3OOH were predicted fromab initio calculations.16,22 Inthis work, fundamental frequencies of methyl hydroperoxwere estimated by normal coordinate calculations using foconstants transferred from the CH3OOCH3 and H2O2 mol-ecules:f O—O 5.000 f O—O—H 0.940 f C—H,H—C—O 20.056f C—O 5.529 f tors~C—O! 0.094 f C—H,H—C—H 0.090f C—H 4.692 f tors~O—O! 0.011 f C—O,H—C—O 0.240f O—H 7.173 f C—H,C—H 0.041 f C—O,C—O—O 1.735f C—O—O 1.512 f C—H,C—O 0.250 f O—O,C—O—O 0.617f H—C—O 0.820 f C—O,O—O 0.267 f O—O,O—O—H 0.919f H—C—H 0.516 f O—O,O—H 20.317 f O—H,O—O—H 0.925

~stretching and stretch-stretch interaction constants areunits of mdyn/Å; bend and torsion constants are in unitsmdyn Å; stretch-bend interaction constants are in unitsmdyn!. The valence force fields for CH3OOCH3 and H2O2

were obtained from normal coordinate calculations usknown vibrational assignments.6,26 Comparison of our fre-quencies with those obtained inab initio calculations16,22

shows satisfactory agreement taking into account thethat theab initio frequencies are unscaled and the anharmnicity contributions are neglected.

The uncertainties in the calculated thermodynamic futions ~Table 8! may reach~2–4! J K21 mol21 for Cp°(T) and~3–5! J K21 mol21 for S°(T). They are caused by the uncetainties in the adopted vibrational frequencies and theproximate model used for internal rotation.

Ideal gas thermodynamic properties of methyl hydropoxide have not been reported previously.

9.3. References

1C. Glidewell, J. Mol. Struct.67, 35 ~1980!.2V. N. Kokorev, N. N. Vyshinskii, V. P. Maslennikov, I. A. Abronin, GM. Zhidomirov, and Yu. A. Aleksandrov, Zh. Strukt. Khim.22, 9 ~1981!.

3M. Jonsson, J. Phys. Chem.100, 6814~1996!.4L. Carballeira, R. A. Mosquera, and M. A. Rios, J. Comput. Chem.9, 851~1988!.

5R. Benassi, U. Folli, S. Sbardellati, and F. Taddei, J. Comput. Chem.14,379 ~1993!.

6K. Chen and N. L. Allinger, J. Comput. Chem.14, 755 ~1993!.7T. P. W. Jungkamp and J. H. Seinfeld, Chem. Phys. Lett.257, 15 ~1996!.


V.

m-94

o

m.

o-

ys.


8S. W. Benson, J. Chem. Phys.40, 1007~1964!.9S. W. Benson, J. Am. Chem. Soc.86, 3922~1964!.

10P. S. Nangia and S. W. Benson, J. Phys. Chem.83, 1138~1979!.11T. H. Lay, L. N. Krasnoperov, C. A. Venanzi, J. W. Bozzelli, and N.

Shokhirev, J. Phys. Chem.100, 8240~1996!.12L. V. Gurvich, I. V. Veyts, and C. B. Alcock,Thermodynamic Properties

of Individual Substances, 4th ed.~Hemisphere, New York, 1991!, Vol. 2.13R. D. Bach, P. Y. Ayala, and H. B. Schlegel, J. Am. Chem. Soc118,

12758~1996!.14J. B. Pedley,Thermochemical Data and Structures of Organic Co

pounds~Thermodynamics Research Center, College Station, TX, 19!,Vol. I.

15G. Baker, J. H. Littlefair, R. Shaw, and J. C. J. Thynne, J. Chem. S6970 ~1965!.

16M. Tyblewski, T. K. Ha, R. Meyer, A. Bauder, and C. E. Blom, J. ChePhys.97, 6168~1992!.


c.

17M. Tyblewski, R. Meyer, and A. Bauder, 8th Colloquium on High Reslution Molecular Spectroscopy, Tours, France, 1983.

18K. Ohkubo, T. Fujita, and H. Sato, J. Mol. Struct.36, 101 ~1977!.19R. A. Bair and W. A. Goddard III, J. Am. Chem. Soc.104, 2719~1982!.20D. Christen, H. G. Mack, and H. Oberhammer, Tetrahedron44, 7363

~1988!.21J. Koller, M. Hodoscek, and B. Plesnicar, J. Am. Chem. Soc.112, 2124

~1990!.22R. Benassi and F. Taddei, Tetrahedron50, 4795~1994!.23B. Haas and H. Oberhammer, J. Am. Chem. Soc.106, 6146~1984!.24R. H. Hunt, R. A. Leacock, C. W. Peters, and K. T. Hecht, J. Chem. Ph

42, 1931~1965!.25L. Radom, W. J. Hehre, and J. A. Pople, J. Am. Chem. Soc.94, 2371

~1972!.26P. G. Giguere and T. K. K. Srinivasan, J. Raman Spectrosc.2, 125~1974!.

e,
TABLE 8. Ideal gas thermodynamic properties of methyl hydroperoxide CH4O2~g! at the standard state pressurp°50.1 MPa (Tr5298.15 K)
T~K!

Cp°~J K21 mol21!

S°~J K21 mol21!

2(G°2H°(Tr))/T~J K21 mol21!


D fH°~kJ mol21!


0 0.000 0.000 ` 213.919 2126.247 2126.247 `25 34.489 171.468 692.887 213.036 2127.153 2125.355 261.91250 35.540 195.488 438.841 212.168 2128.683 2123.025 128.52275 38.512 210.437 360.349 211.243 2130.278 2119.836 83.460

100 41.627 221.948 324.360 210.241 2131.534 2116.158 60.674

150 46.975 239.876 293.352 28.021 2133.584 2108.013 37.613180 49.820 248.694 285.189 26.569 2134.723 2102.791 29.829190 50.758 251.413 283.340 26.066 2135.098 2101.007 27.768200 51.703 254.040 281.810 25.554 2135.472 299.203 25.909

210 52.659 256.586 280.549 25.032 2135.845 297.380 24.222220 53.627 259.058 279.516 24.501 2136.215 295.540 22.684230 54.610 261.463 278.679 23.960 2136.583 293.683 21.276240 55.609 263.808 278.011 23.408 2136.949 291.810 19.982250 56.624 266.099 277.489 22.847 2137.312 289.922 18.788

260 57.653 268.340 277.094 22.276 2137.671 288.019 17.683270 58.696 270.535 276.810 21.694 2138.026 286.103 16.657280 59.751 272.689 276.625 21.102 2138.376 284.173 15.703290 60.816 274.804 276.526 20.499 2138.722 282.231 14.811

298.15 61.690 276.502 276.502 0.0002139.000 280.640 14.128

300 61.889 276.884 276.503 0.114 2139.063 280.277 13.977350 67.290 286.830 277.276 3.344 2140.679 270.350 10.499400 72.583 296.163 279.059 6.841 2142.143 260.202 7.861450 77.604 305.005 281.455 10.597 2143.453 249.879 5.790500 82.279 313.427 284.234 14.596 2144.620 239.418 4.118

600 90.573 329.181 290.432 23.250 2146.559 218.190 1.584700 97.633 343.688 297.017 32.670 2148.043 3.328 20.248800 103.693 357.130 303.701 42.743 2149.133 25.032 21.634900 108.935 369.654 310.342 53.381 2149.884 46.850 22.719

1000 113.485 381.372 316.865 64.5072150.352 68.737 23.590

1100 117.439 392.378 323.235 76.0582150.582 90.659 24.3051200 120.878 402.748 329.433 87.9782150.618 112.593 24.9011300 123.871 412.544 335.453 100.2192150.500 134.525 25.4051400 126.478 421.822 341.294 112.7392150.261 156.442 25.8371500 128.752 430.627 346.958 125.5032149.928 178.338 26.210

1600 130.741 439.001 352.451 138.4802149.526 200.219 26.5361700 132.485 446.981 357.779 151.6432149.075 222.061 26.8231800 134.018 454.598 362.948 164.9702148.588 243.882 27.0771900 135.369 461.881 367.965 178.4412148.080 265.672 27.3042000 136.564 468.855 372.836 192.0392147.563 287.436 27.507




10. Dimethyl Peroxide, CH 3AOAOACH3

Dimethyl peroxide (C2H6O2) Ideal gas Mr562.0682D fH°(0 K)52106.565.0 kJ mol21


Molecular constants

Point group:C2 Symmetry number:s52 Number of optical isomers:n52Ground electronic state: X 1A Energy:eX50 cm21 Quantum weight:gX51



A n1 2945 1 n13 . . . b 1n2 2917 1 B n14 3000 1n3 2900 1 n15 2965 1n4 1487 1 n16 2818 1n5 1474 1 n17 1483 1n6 1433 1 n18 1433 1n7 1198 1 n19 1430 1n8 1165 1 n20 1119 1n9 1020 1 n21 1112 1n10 786 1 n22 1032 1n11 448 1 n23 376 1n12 ¯

a 1 n24 ¯

a 1

aInstead of torsional modesn125218 cm21 and n245231 cm21, thecontributions due to the internal rotation of CH3 groups around C—Obonds were calculated from the potentialV(w)5 1

2V3(12cos 3w), wherew is the H—C—O—O torsional angle andV35900 cm21.bInstead of torsional moden13573 cm21, the contributions due to theinternal rotation of OCH3 group around O—O bond were calculatedfrom the potentialV(w)5V01V1 cosw1V2 cos 2w1V3 cos 3w, wherewis the C—O—O—C torsional angle,V051341.3, V152081.0, V2

51052.2, andV35225.5~in cm21!.


OCH3 top: Reduced moment of inertia,I r51.5928310239 g cm2, Symmetry number,sm51.

Geometryr (C—O)51.42060.007 År (O—O)51.45760.012 År (C—H)51.09960.004 Å/C—O—O5105.260.5°/H—C—H5110.160.7°f(C—O—O—C)511964°


-

fof


The enthalpy of formation of dimethyl peroxide recommended in this work~2125.5 kJ mol21! was de-termined by Bakeret al.1 from calorimetric measurements othe enthalpy of combustion. Slightly lower values



D fH° ~298.15 K! from 2129.3 kJ mol21 to 2133.9 kJ mol21

were estimated by group additivity2,3 and molecularmechanics calculations.4,5A lower value is estimatedfrom the experimental value ofD fH°(CH3O) Gurvichet al.6 and the bond energy for the O—O bond inCH3OOCH3:

7


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D fH°~CH3OOCH3!52D fH°~CH3O!

2D°~CH3O—OCH3!

52313– 16052134 kJ mol21.

A still more negative value,2138.1 kJ mol21, was proposedby Benassiet al.8 employing theoretical and empirical approaches. Semiempirical MINDO9,10 and molecularmechanics11 calculations provideD fH° ~298.15 K! values,2105.1 to2121.6 kJ mol21, which are greater than the experimental value. The available theoretical and empirievaluations are grounds to believe that the experimevalue of D fH° ~298.15 K! may be overestimated. Thus, iuncertainty was increased in this work.


The molecular structure of dimethyl peroxidCH3OOCH3, was studied by electron diffraction.12 The mo-lecular intensities were analyzed using a model which csidered the internal rotation about the O—O bond. The equi-librium geometry was determined to be theskewconformation with a C—O—O—C dihedral angle of 119°The barrier in the trans configuration (/C—O—O—C5180°) was found to be 87187/252 cm21. This result agreeswith an analysis of infrared and Raman spectra13 and a nor-mal coordinate analysis based on the these data14 as well aswith results of semiempirical,9,10,15,16ab initio17–19 and mo-lecular mechanics4,5,8 calculations. Photoelectron spectinvestigations20,21 andab initio calculations8,22–24support anexactly planar or nearly planartransconfiguration. However,it should be noted that the value of a dihedral angle depestrongly on the basis set and method used.19 Hamada andMorishita25 have described the Raman and infrared speof CH3OOCH3 in terms of planar structure ofD3h symmetry.In this work, the product of the principal moments of inerof dimethyl peroxide forskewconformation ofC2 symmetrywas calculated using the structural parameters determfrom electron diffraction study.12

The dimethyl peroxide molecule undergoes three laramplitude motions: an internal rotation of the OCH3 groupsabout the O—O bond and internal rotation of the CH3 groupsabout two C—O bonds. Contributions to the thermodynamproperties from these hindered rotors were calculated inwork based on available data on the rotational barriersCH3OOCH3. The value ofV35900 cm21 was accepted forthe internal rotation barrier of methyl groups around the Cbonds. This value was used by Koput26 in his theoreticalmodel describing the internal rotation in dimethyl peroxiand it is the average of the results of molecular mechacalculations.4 The double-minimum potential energy funtion,


was used in this work for the internal rotation around tO—O bond. This function was chosen earlier for the hdered rotation potential function in hydrogen peroxide.27 Theexpansion coefficientsV0 , V1 , V2 , andV3 can be expresse


lal

-

ds

ra

ed

-

isin

s

-

in terms of thetrans barrier heightVtrans , the cis barrierheightVcis , and the COOC dihedral anglewe correspondingto a minimum of the potential function.27 The values ofV0 ,V1 , V2 , and V3 were calculated in this work assuminVtrans587 cm21, Vcis54700 cm21, and we5119°. Thevalue of Vtrans was taken from the electron diffractiostudy.12 It agrees with results of theoretical calculations4,5,8,19

within the limits of experimental accuracy. The adoptvalue ofVcis is based on results ofab initio8,18and molecularmechanics4,5 calculations. The values of the reduced mments of inertia for CH3 and OCH3 tops were calculatedfrom structural parameters given above.

Christe13 has investigated the infrared spectraCH3OOCH3 and CD3OOCD3 both in the gas phase and in aAr matrix and the Raman spectra of these molecules inliquid phase. The vibrational assignment proposedChriste13 has considerable uncertainty for a number of tvibrations, and the low-frequency modes were not assigat all. Bell and Laane14 have carried out a normal coordinaanalysis of dimethyl peroxide using the experimental dataChriste.13 Hamada and Morishita25 have described the vibrational spectra of CH3OOCH3 in terms of D3h symmetry.However, this assignment is in conflict with available infomation on dimethyl peroxide. There are twoab initio calcu-lations of vibrational frequencies of CH3OOCH3.

23,28Resultsof Benassi and Taddei23 show overall agreement with expermental data taking into account the fact that theab initiofrequencies are unscaled and the anharmonicity contributare neglected. Chen and Allinger5 have carried out the molecular mechanics calculation of vibrational frequenciesdimethyl peroxide. Their results are in agreement withavailable, but somewhat tentative and incomplete, expmental data.13 The assignment proposed by Chen aAllinger5 is accepted in this work.

The uncertainties in the calculated thermodynamic futions ~Table 9! may reach~2–4! J K21 mol21 for Cp°(T) and~3–5! J K21 mol21 for S°(T). They are caused by uncertainties in the adopted vibrational frequencies and the apprmate treatment of internal rotation.

Ideal gas thermodynamic properties of dimethyl peroxhave not been reported previously.

10.3. References

1G. Baker, J. H. Littlefair, R. Shaw, and J. C. J. Thynne, J. Chem. S6970 ~1965!.

2S. W. Benson, J. Chem. Phys.40, 1007~1964!.3S. W. Benson, J. Am. Chem. Soc.86, 3922~1964!.4L. Carballeira, R. A. Mosquera, and M. A. Rios, J. Comput. Chem.9, 851~1988!.

5K. Chen and N. L. Allinger, J. Comput. Chem.14, 755 ~1993!.6L. V. Gurvich, I. V. Veyts, and C. B. Alcock,Thermodynamic Propertiesof Individual Substances, 4th ed.~Hemisphere, New York, 1991!, Vol. 2.

7R. D. Bach, P. Y. Ayala, and H. B. Schlegel, J. Am. Chem. Soc.118,12758~1996!.

8R. Benassi, U. Folli, S. Sbardellati, and F. Taddei, J. Comput. Chem.14,379 ~1993!.

9C. Glidewell, J. Mol. Struct.67, 35 ~1980!.



.

r.

oc ys.

k.


10V. N. Kokorev, N. N. Vyshinskii, V. P. Maslennikov, I. A. Abronin, GM. Zhidomirov, and Yu. A. Aleksandrov, Zh. Strukt. Khim.22, 9 ~1981!.

11W. H. Richardson, J. Org. Chem.54, 4677~1989!.12B. Haas and H. Oberhammer, J. Am. Chem. Soc.106, 6146~1984!.13K. O. Christe, Spectrochim. Acta A27, 463 ~1971!.14M. E. B. Bell and J. Laane, Spectrochim. Acta A28, 2239~1972!.15R. M. Minyaev, V. I. Minkin, I. I. Zakharov, and I. D. Sadekov, Teo

Eksp. Khim.9, 816 ~1973!.16K. Ohkubo, T. Fujita, and H. Sato, J. Mol. Struct.36, 101 ~1977!.17B. Plesnicar, D. Kocjan, S. Murovec, and A. Azman, J. Am. Chem. S

98, 3143~1976!.18W. Gase and J. E. Boggs, J. Mol. Struct.116, 207 ~1984!.19D. Christen, H. G. Mack, and H. Oberhammer, Tetrahedron44, 7363

~1988!.



.

20K. Kimura and K. Osafune, Bull. Chem. Soc. Jpn.48, 2421~1975!.21P. Rademacher and W. Elling, Liebigs Ann. Chem. 1473~1979!.22R. A. Bair and W. A. Goddard III, J. Am. Chem. Soc.104, 2719~1982!.23R. Benassi and F. Taddei, Tetrahedron50, 4795~1994!.24M.-B. Huang and H. U. Suter, J. Mol. Struct: THEOCHEM337, 173

~1995!.25K. Hamada and H. Morishita, Spectrosc. Lett.13, 185 ~1980!.26J. Koput, J. Mol. Spectrosc.141, 118 ~1990!.27R. H. Hunt, R. A. Leacock, C. W. Peters, and K. T. Hecht, J. Chem. Ph

42, 1931~1965!.28G. A. Pitsevich, V. I. Gogolinskii, and I. P. Zyatkov, Zh. Prikl. Spektros

56, 643 ~1992!.

e,
TABLE 9. Ideal gas thermodynamic properties of dimethyl peroxide C2H6O2~g! at the standard state pressurp°50.1 MPa (Tr5298.15 K)
T~K!

Cp°~J K21 mol21!

S°~J K21 mol21!

2(G°2H°(Tr))/T~J K21 mol21!


D fH°~kJ mol21!


0 0.000 0.000 ` 217.153 2106.460 2106.460 `25 38.665 180.406 831.484 216.277 2107.908 2104.953 219.28450 42.071 208.414 513.657 215.262 2110.130 2101.224 105.74775 45.713 226.123 415.019 214.167 2112.460 296.245 67.030

100 49.953 239.851 369.568 212.972 2114.304 290.552 47.299

150 58.133 261.681 330.120 210.266 2117.336 278.000 27.162180 62.664 272.683 319.647 28.453 2119.030 269.973 20.305190 64.145 276.111 317.266 27.819 2119.590 267.232 18.483200 65.624 279.439 315.292 27.171 2120.149 264.462 16.836

210 67.105 282.676 313.662 26.507 2120.707 261.664 15.338220 68.594 285.832 312.325 25.828 2121.264 258.840 13.970230 70.095 288.915 311.241 25.135 2121.818 255.990 12.716240 71.609 291.930 310.374 24.426 2122.370 253.116 11.560250 73.139 294.884 309.695 23.703 2122.919 250.219 10.493

260 74.685 297.783 309.181 22.964 2123.465 247.301 9.503270 76.247 300.630 308.812 22.209 2124.006 244.360 8.582280 77.823 303.432 308.570 21.439 2124.542 241.401 7.723290 79.413 306.190 308.441 20.652 2125.072 238.422 6.921

298.15 80.717 308.409 308.409 0.0002125.500 235.981 6.304

300 81.014 308.910 308.411 0.150 2125.597 235.425 6.168350 89.107 322.005 309.427 4.402 2128.110 220.196 3.014400 97.131 334.429 311.782 9.059 2130.424 24.619 0.603450 104.858 346.320 314.963 14.1102132.528 11.235 21.304500 112.164 357.750 318.674 19.5382134.426 27.313 22.853

600 125.390 379.396 327.012 31.4312137.633 59.970 25.221700 136.887 399.609 335.955 44.5582140.119 93.110 26.948800 146.892 418.557 345.108 58.7592141.956 126.561 28.263900 155.605 436.373 354.269 73.8932143.219 160.207 29.298

1000 163.187 453.169 363.327 89.8422143.993 193.966210.132

1100 169.774 469.039 372.223 106.4982144.351 227.782210.8161200 175.490 484.062 380.922 123.7682144.366 261.615211.3881300 180.449 498.309 389.409 141.5702144.105 295.441211.8711400 184.752 511.843 397.673 159.5362143.625 329.235212.2841500 188.491 524.721 405.719 178.5022142.971 362.990212.640

1600 191.746 536.992 413.543 197.5182142.187 396.716212.9511700 194.585 548.703 421.152 216.8382141.305 430.365213.2231800 197.069 559.898 428.551 236.4232140.351 463.971213.4641900 199.247 570.612 435.748 256.2412139.347 497.516213.6772000 201.164 580.882 442.750 276.2642138.314 531.010213.868



11. Diacetyl Peroxide, CH 3ACOAOAOACO—CH3

Diacetyl peroxide (C4H6O4) Ideal gas Mr5118.089D fH°(0 K)52(477.0610.0) kJ mol21

S°(298.15 K)5(390.766.0) J K21 mol21 D fH°(298.15 K)52(500.0610.0) kJ mol21

Molecular constants

Point group:C2 Symmetry number:s52 Number of optical isomers:n52Ground electronic state: X 1A Energy:eX50 cm21 Quantum weight:gX51



A n1 3001 1 n19 ¯

b 1n2 2998 1 B n20 3001 1n3 2934 1 n21 2998 1n4 1762 1 n22 2934 1n5 1466 1 n23 1749 1n6 1428 1 n24 1457 1n7 1426 1 n25 1427 1n8 1290 1 n26 1426 1n9 1087 1 n27 1285 1n10 927 1 n28 962 1n11 875 1 n29 922 1n12 850 1 n30 808 1n13 648 1 n31 639 1n14 631 1 n32 619 1n15 392 1 n33 545 1n16 285 1 n34 328 1n17 151 1 n35 140 1n18 ¯

a 1 n36 ¯

b 1

aInstead of torsional moden18;70 cm21, the contributions due to theinternal rotation of O—CO—CH3 group around O—O bond were calcu-lated from the potentialV(w)5V01V1 cosw1V2 cos2w1V3 cos3w,wherew is the C—O—O—C torsional angle,V051433.9,V152222.2,V251111.1, andV35232.8~in cm21!.bInstead of torsional modesn19 andn36;60 cm21, the contributions dueto the internal rotation of CH3 groups around C—C bonds were calcu-lated from the potentialV(w)5 1

2V3(12cos 3w), where w is theH—C—C—O torsional angle andV3580 cm21.

O—CO—CH3 top: Reduced moment of inertia,I r54.5200310239 g cm2, Symmetry number,sm51.


Geometryr ~C—C!51.49560.01 Å /OvC—O512263°r ~CvO!51.2160.02 Å /C—O—O511363°r ~C—O!51.3460.02 Å /H—C—H5109.562.0°r ~O—O!51.4660.02 Å w~C—O—O—C!5120610°r ~C—H!51.0960.01 Å w~OvC—O—O!50°/C—CvO512863°




-

tioza

o

s

y

omi-e

ity-is

na

l-ac

kal

te

ith

e-

ion

id.

en-

e

f

ted

-

are

al

ofcef-

edn-

o-of

.6u-



Jaffeet al.1 determined the enthalpy of formation for liquid diacetyl peroxide (CH3CO—OO—COCH3) from calori-metric measurements. Assuming the enthalpy of vaporizaof diacetyl peroxide to be equal to the enthalpy of vaporition of acetic anhydride (CH3CO—O—COCH3), the authorsobtained the value of2498 kJ mol21 for the enthalpy offormation of gaseous diacetyl peroxide. A similar valueD fH°(298.15 K)52502 kJ mol21 may be derived from thegroup additivity contributions for peroxyacids and peroxyeters obtained by Benassi and Taddei2 using empirical ap-proaches andab initio calculations. The value predicted bthe method of group equations,

D fH°~CH3CO—OO—COCH3!

5D fH°~CH3CO—O—COCH3!1D fH°~CH3OOCH3!

2D fH°~CH3OCH3!5~2572.5!1~2125.5!

2~2184.1!52513.9

~theD fH° values for the related compounds were taken frthe compilation by Pedley3!, agrees with the two above estmates within the limits of the combined errors of those dterminations. Considerably lower values ofD fH° for di-acetyl peroxide were estimated from a group additivapproximation~2540 kJ mol21!4 and a semiempirical calculation ~;2585 kJ mol21!.5,6 The value recommended in thwork, 2(500610) kJ mol21, is based on the estimates.1,2


Experimental data on molecular structure and vibratiofrequencies of diacetyl peroxide, CH3CO—OO—COCH3,are unknown. Semiempirical MINDO calculations5 predictthat the skew conformation of C2 symmetry with aC—O—O—C dihedral angle of 108° is the most stable. Athough a planar structure was suggested for the peroxygroup in peroxyacetic acid from a microwave study,7 theskewconformation ofC2 symmetry is accepted in this worfor diacetyl peroxide in accord with a semiempiriccalculation5 and by analogy with dimethyl peroxide.8 Theproduct of the principal moments of inertia was calcula



n-

f

-

-

l

id

d

from structural parameters estimated by comparison wstructural parameters of CH3CO—OOH,7

CH3CO—O—COCH3,9 and CH3OOCH3.

8

The diacetyl peroxide molecule undergoes five largamplitude motions: an internal rotation about a central O—Obond and about two C—C and two C—O bonds. Contribu-tions to the thermodynamic functions due to internal rotatof CH3 groups were calculated in this work assuming theV3

barrier height to be the same as that in peroxyacetic ac7

The double-minimum potential energy function,


was used for the internal rotation about the O—O bond. Thisfunction was chosen earlier for the hindered rotation pottial function in hydrogen peroxide.10 The expansion coeffi-cientsV0 , V1 , V2 , andV3 can be expressed in terms of thtrans barrier heightVtrans , the cis barrier heightVcis , andthe COOC dihedral anglewe corresponding to a minimum othe potential function.10 The values ofV0 , V1 , V2 , andV3

were calculated in this work assumingVtrans590 cm21,Vcis55000 cm21, and we5120°. The values ofVtrans andVcis are derived from the results of a MINDO calculation5

taking into account that the same calculation overestimathe Vtrans and underestimated theVcis barriers for theCH3OOH and CH3OOCH3 molecules. The values of the reduced moments of inertia for CH3 and CH3COO tops werecalculated from structural parameters given above. Thereno data on barriers hindering the internal rotation of CH3COgroups about the C-O bonds. Frequenciesn175151 andn35

5140 cm21 were accepted in this work for the torsionmotion about the C-O bonds.

Zyatkovet al.11 have calculated vibrational frequenciesdiacetyl peroxide using a theoretical simulation of the forfield. In this work, vibrational frequencies oCH3CO—OO—COCH3 were calculated using force constants transferred from the CH3CO—OOH molecule. Thesimplified valence force field for that molecule was obtainby normal coordinate calculations for the vibrational assigment of Cugleyet al.12 The calculated force constants reprduce the observed vibrational wave numbersCH3CO—OOH with a root mean square deviation of 0cm21. The following 18 force constants were used for calclating the vibrational frequencies of diacetyl peroxide:

f O—O 3.821 f C—C—O 2.363 f tors~C—O! 0.430

f C—O 3.827 f OvC—O5 f OvC—C 1.972 f tors~O—O! 0.104

f CvO 11.382 f C—C—H 0.497 f CvO,C—C5 f CvO,C—O 1.679

f C—C 3.480 f H—C—H 0.523 f C—C,C—O 20.356

f C—H 4.836 f wag~CvO! 0.515 f C—H,C—C—H 0.415

f C—O—O 1.659 f tors~C—C! 0.006 f C—O,OvC—O 0.232


enta

nc

eth

id

-94

E.

.

ct.

ys.

.


~stretching and stretch-stretch interaction constants arunits of mdyn/Å; bending, wagging, and torsion constaare in units of mdyn Å; stretch-bend interaction constantsin units of mdyn!.

The uncertainties in the calculated thermodynamic futions ~Table 10! may reach~8–12! J K21 mol21 for Cp°(T)and ~6–10! J K21 mol21 for S°(T). They are caused by thuncertainties in the adopted vibrational frequencies andapproximate treatment of internal rotation.

Ideal gas thermodynamic properties of diacetyl peroxhave not been reported previously.

11.3. References

1L. Jaffe, E. L. Prosen, and M. Szware, J. Chem. Phys.27, 416 ~1957!.2R. Benassi and F. Taddei, J. Mol. Struct.: THEOCHEM303, 101 ~1994!.


insre

-

e

e


4S. W. Benson, F. R. Cruickshank, D. M. Golden, G. R. Haugen, H.O’Neal, A. S. Rodgers, R. Shaw, and R. Walsh, Chem. Rev.69, 279~1969!.

5C. Glidewell, J. Mol. Struct.67, 35 ~1980!.6V. N. Kokorev, N. N. Vyshinskii, V. P. Maslennikov, I. A. Abronin, GM. Zhidomirov, and Yu. A. Aleksandrov, Zh. Strukt. Khim.22, 9 ~1981!.

7J. A. Cugley, W. Bossert, A. Bauder, and H. H. Gu¨nthard, Chem. Phys.16, 229 ~1976!.

8B. Haas and H. Oberhammer, J. Am. Chem. Soc.106, 6146~1984!.9H. J. Vledder, F. C. Mijlhoff, J. C. Leyte, and C. Romers, J. Mol. Stru7, 421 ~1971!.

10R. H. Hunt, R. A. Leacock, C. W. Peters, and K. T. Hecht, J. Chem. Ph42, 1931~1965!.

11I. P. Zyatkov, V. I. Gogolinskii, V. V. Sivchik, and D. I. Sagaidak, ZhPrikl. Spektrosk.29, 652 ~1978!.

12J. A. Cugley, R. Meyer, and H. H. Gu¨nthard, Chem. Phys.18, 281~1976!.

e,
TABLE 10. Ideal gas thermodynamic properties of diacetyl peroxide, C4H6O4~g! at the standard state pressurp°50.1 MPa (Tr5298.15 K)
T~K!

Cp°~J K21 mol21!

S°~J K21 mol21!

2(G°2H°(Tr))/T~J K21 mol21!


D fH°~kJ mol21!


0 0.000 0.000 ` 223.944 2476.961 2476.961 `25 50.640 213.740 1130.731 222.925 2478.990 2473.540 989.39550 58.035 251.723 682.615 221.545 2481.588 2467.166 488.03875 62.084 276.009 543.259 220.044 2484.278 2459.352 319.917

100 66.834 294.500 478.840 218.434 2486.503 2450.697 235.417

150 78.569 323.725 422.461 214.810 2490.316 2431.949 150.416180 86.766 338.764 407.276 212.332 2492.443 2420.074 121.901190 89.636 343.532 403.796 211.450 2493.135 2416.035 114.374200 92.559 348.204 400.900 210.539 2493.820 2411.959 107.591210 95.524 352.791 398.500 29.599 2494.496 2407.849 101.446220 98.523 357.304 396.525 28.629 2495.163 2403.707 95.851

230 101.547 361.750 394.917 27.628 2495.821 2399.536 90.736240 104.588 366.136 393.626 26.598 2496.468 2395.336 86.041250 107.640 370.468 392.614 25.536 2497.104 2391.109 81.717

260 110.696 374.749 391.844 24.445 2497.729 2386.857 77.720270 113.750 378.984 391.290 23.323 2498.342 2382.581 74.014280 116.796 383.176 390.925 22.170 2498.943 2378.283 70.569290 119.830 387.327 390.730 20.987 2499.530 2373.963 67.357

298.15 122.291 390.682 390.682 0.0002500.000 2370.427 64.896

300 122.848 391.441 390.685 0.227 2500.105 2369.622 64.356350 137.551 411.491 392.235 6.740 2502.777 2347.661 51.885400 151.377 430.772 395.855 13.9672505.120 2325.337 42.484450 164.144 449.350 400.773 21.8602507.157 2302.738 35.141500 175.813 467.258 406.531 30.3632508.918 2279.929 29.244

600 196.085 501.163 419.512 48.9902511.704 2233.859 20.359700 212.888 532.691 433.456 69.4652513.643 2187.388 13.983800 226.936 562.062 447.717 91.4762514.847 2140.688 9.186900 238.778 589.495 461.963 114.7782515.418 293.879 5.449

1000 248.823 615.187 476.014 139.1722515.458 247.036 2.457

1100 257.379 639.314 489.774 164.4932515.048 20.210 0.0101200 264.693 662.031 503.192 190.6062514.271 46.561 22.0271300 270.965 683.471 516.243 217.3972513.201 93.260 23.7471400 276.360 703.754 528.919 244.7702511.906 139.862 25.2181500 281.017 722.984 541.221 272.6452510.431 186.370 26.490

1600 285.051 741.252 553.157 300.9532508.834 232.810 27.6001700 288.556 758.641 564.737 329.6372507.144 279.105 28.5761800 291.613 775.223 575.973 358.6492505.392 325.314 29.4401900 294.288 791.063 586.880 387.9472503.606 371.413210.2112000 296.638 806.219 597.471 417.4962501.807 417.423210.902



re,


J. Phys. Chem. Ref

Dow

TABLE 11. Summary of the thermodynamic properties at 298.15 K and the standard state pressup°50.1 MPa

MoleculeS° ~298.15 K!~J K21 mol21!

Cp° ~298.15 K!~J K21 mol21!

D fH° ~298.15 K!~kJ mol21!

Bromoacetic acid 337.06 5.0 80.5 6 3.0 2383.5 6 3.1Chloroacetic acid 325.96 5.0 78.8 6 3.0 2427.6 6 1.0Oxopropanedinitrile 310.06 1.0 80.8 6 1.0 247.5 6 6.4Glycolic acid 318.66 5.0 87.1 6 3.0 2583.0 6 10.0Glyoxal 272.5 6 1.0 60.6 6 0.5 2212.0 6 0.8Cyanooxomethyl radical 278.26 1.5 56.1 6 1.5 210.0 6 10.0Oxalic acid 320.66 5.0 86.2 6 5.0 2731.8 6 2.0Methyl hydroperoxide 276.56 3.0 61.7 6 2.0 2139.0 6 5.0Dimethyl peroxide 308.46 3.0 80.7 6 2.0 2125.5 6 5.0Diacetyl peroxide 390.76 6.0 122.3 6 8.0 2500.0 6 10.0

le

onec

d

alewioydeuc

cya

orknal

d,t-istsE.

sors

lmTes-

12. Conclusions

The thermodynamic properties of 10 organic molecuhave been calculated, based on the critical evaluationavailable thermodynamic and spectroscopic informatiWhere no data were available, estimation techniques wused. Recommended values for the entropy, heat capaand the enthalpy of formation at 298.15 K are summarizeTable 11.

For a first round of new experimental studies, substantiimproved formation properties could be obtained with nor confirming measurements for the enthalpy of formatfor bromoacetic acid, glycolic acid, the cyanooxomethradical, and the three peroxides—methyl hydroperoxidimethyl peroxide, and diacetyl peroxide. In order to calclate significantly more reliable thermal functions, the struture and the vibrational frequencies are needed for thenooxomethyl radical and diacetyl peroxide, since these dwere estimated for these two compounds.

. Data, Vol. 30, No. 2, 2001


sof.reity,in

ly

nl,--a-ta

13. Acknowledgments

The authors wish to acknowledge the support of this wby the Upper Atmospheric Research Program of the NatioAeronautics and Space Administration~NASA! and theStandard Reference Data~SRD! Program of the National In-stitute of Standards and Technology~NIST!. The authorsthank Professor Joel Liebman of the University of MarylanBaltimore County, for bringing to their attention the juspublished work, so relevant to this article, of the 10 scientof Portugal and Germany working with Professor ManuelMinas da Piedade of the Centro de Quı´mica Estrutural, Com-plexo Interdisciplinar, at the Institutio Superior Te´cnico, Lis-bon, Portugal. The authors are also grateful to ProfesVladimir Yungman of the Institute for High Temperature~IVTAN ! of the Russian Academy of Sciences, Dr. MalcoW. Chase of SRD, and Dr. Eugene S. Domalski of NISwhose expert advice, support, and encouragement weresential to the completion of this project.

ove but

rium

tional

hane,. Ther-

ics of

-

14. Extended Bibliographies

The following bibliography lists articles that were found in the literature pertaining to the molecules discussed abwere not used as sources of information in the evaluations.

14.1. Extended Bibliography for Bromoacetic Acid, C 2H3BrO2

71KIN/GOL King, K. D., Golden, D. M., and Benson, S. W., ‘‘Thermochemistry of the gas-phase equilibCH3COCH31Br25CH3COCH21HBr,’’ J. Chem. Thermodyn.3, 129–134~1971!.

78VAN/BRA Van Eijck, B. P., Brandts, P., Maas, J. P. M., ‘‘Microwave spectra and molecular structures of rotaisomers of fluoroacetic acid and fluoroacetyl fluoride,’’ J. Mol. Struct.44, 1–13~1978!.

93CAR/LAY Carson, A. S., Laye, P. G., Pedley, J. B., Welsby, A. M., ‘‘The enthalpies of formation of iodometdiiodomethane, triiodomethane, and tetraiodomethane by rotating combustion calorimetry,’’ J. Chemmodyn.25, 261–269~1993!.

14.2. Extended Bibliography for Chloroacetic Acid, C 2H3ClO2

64JOH Johansen, H., ‘‘Normal coordinate analysis of polyatomic molecules and statistical thermodynamisotopic molecules,’’ Z. Phys. Chem.227, 305–328~1964!.

75CHA/DEV Chandramani, R., Devaraj, N., ‘‘Torsional-vibration frequency ina-CH2ClCOOH and its temperature dependence from pure quadrupole resonance measurements,’’ Indian J. Pure Appl. Phys.13, 637–638~1975!.

75SIN/KAT Sinha, D., Katon, J. E., Jakobsen, R. J., ‘‘The vibrational spectra and structure ofb- and g-chloroaceticacid,’’ J. Mol. Struct.24, 279–291~1975!.


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86FAU/TEI2 Fausto, R., Teixeira-Dias, J. J. C., ‘‘Conformational and vibrational spectroscopic analysis of CHC2COXand CCl3COX ~X5Cl, OH, OCH3!,’’ J. Mol. Struct. 144, 241–263~1986!.

93KUL/FAU Kulbida, A., Fausto, R., ‘‘Conformers, vibrational spectra and infrared-induced rotamerization of dichacetic acid in argon and krypton matrixes,’’ J. Chem. Soc., Faraday Trans.89, 4257–4266~1993!.

96NYQ/CLA Nyquist, R. A., Clark, T. D., ‘‘Infrared study ofa-haloacetic acids in solution,’’ Vib. Spectrosc.10, 203–228~1996!.

14.3. Extended Bibliography for Oxopropanedinitrile, C 3N2O

53KEM/TRA Kemula, W., Tramer, A., ‘‘Vibrational specrum of carbonyl cyanide,’’ Roczniki Chem.27, 522–523~1953!.70NAY/ARU Nayar, V. U., Aruldhas, G., ‘‘Force field and Coriolis coupling coefficients of carbonyl cyanide,’’ India

Pure Appl. Phys.8, 840–841~1970!.71DUN/WHI Duncan, A. B. F., Whitlock, R. F., ‘‘Vacuum ultraviolet absorption spectrum of carbonyl cyanide,’’ S

trochim. Acta A27, 2539–2541~1971!.72NAY/ARU Nayar, V. U., Aruldhas, G., Joseph, K. B., Cyvin, S. J., ‘‘Vibrational analyses and mean amplitudes for

simple molecules. III. Carbonyl cyanide,’’ Mol. Struct. Vib. 237–242~1972!.97LER/DEW Leroy, G., Dewispelaere, J. P., Wilante, C., Benkadour, H., ‘‘A theoretical approach to the thermoche

of the polymerization of some derivatives of the monomers CH25X ~X5CH2, NH, O!,’’ Macromol. TheorySimul. 6, 729–739~1997!.

97MED/BHA Medhi, C., Bhattacharyya, S. P., ‘‘Transcription of the results of quantum calculations in terms oclassical notion of molecular structures: The cases of some small carbonyls in the ground andstates,’’ Proc. Indian Acad. Sci., Chem. Sci.109, 61–70~1997!.

14.4. Extended Bibliography for Glycolic Acid, C 2H4O3

87KAK Kakumoto, T., ‘‘A theoretical study on the unimolecular decomposition of somea-dicarbonyl compoundsglyoxal, oxalic acid and glycolic acid,’’ J. Sci. Hiroshima Univ. A51, 69–111~1987!.

93DOM/HEA Domalski, E. S., Hearing, E. D., ‘‘Estimation of the thermodynamic properties of C-H-N-O-S-halcompounds at 298.15 K,’’ J. Phys. Chem. Ref. Data22, 805–1159~1993!.

14.5. Extended Bibliography for Glyoxal, C 2H2O2

39LUV/SCH LuValle, J. E., Schomaker, V., ‘‘The molecular structures of glyoxal and dimethyl glyoxal by the elediffraction method,’’ J. Am. Chem. Soc.61, 3520–3525~1939!.

49COL/THO Cole, A. R. H., Thompson, H. W., ‘‘Vibration-rotation bands of some polyatomic molecules,’’ Proc. R.London, Ser. A,200, 10–20~1949!.

54BRA/MIN Brand, J. C. D., Minkoff, G. J., ‘‘The infrared spectrum of dideuteroglyoxal,’’ J. Chem. Soc. 2970–~1954!.

64COL/OSB Cole, A. R. H., Osborne, G. A., ‘‘Fundamentaln12 of glyoxal,’’ J. Chem. Soc. 1532~1964!.69JEN/HAG Jensen, H. H., Hagen, G., Cyvin, S. J., ‘‘Mean amplitudes of vibration for some conjugated ca

compounds: glyoxal, acrolein, andp-benzoquinone,’’ J. Mol. Struct.4, 51–58~1969!.71AGA/BAI Agar, D. M., Bair, E. J., Birss, F. W., Borrell, P., Chen, P. C., Currie, G. N., McHugh, A. J., Orr, B

Ramsay, D. A., Roncin, J. Y.,‘‘The 4550 Å band system of glyoxal. III. Vibration-rotational analyses fobands of C2D2O2,’’ Can. J. Phys.49, 323–327~1971!.

73DON/RAM Dong, R. Y., Ramsay, D. A., ‘‘A band system of glyoxal-d1 and glyoxal-d2 ,’’ Can. J. Phys.51, 1463–1465~1973!.

73GLE/MCC Gleghorn, J. T., McConkey, F. W., ‘‘The structure and properties of carbonyl compounds,’’ J. Mol. S18, 219–225~1973!.

73LE/TYU Le, H. H., Tyulin, V. I., ‘‘Raman spectrum of liquid glyoxal (C2O2H2),’’ Opt. Spektrosk.35, 770–772~1973!.

75COL/DUR Cole, A. R. H., Durig, J. R., ‘‘Raman and infrared spectra of solid glyoxal-d1 and glyoxal-d2 ,’’ J. RamanSpectrosc.4, 31–39~1975!.

75GUT/BAU Gut, M., Bauder, A., Gu¨nthard H. H., ‘‘Solution of the rotation-internal rotation problem of glyoxal tymolecules by infinite matrix technique,’’ Chem. Phys.8, 252–271~1975!.

75PAN Pancir, J., ‘‘Cis-transisomerization of glyoxal. A contribution to the rehabilitation of semiempirical meods,’’ Theor. Chim. Acta40, 81–83~1975!.

76COL/CRO Cole, A. R. H., Cross, K. J., Ramsay, D. A., ‘‘Rotational structure of the~0–0! visible band of glyoxal-d1 .A reanalysis,’’ J. Phys. Chem.80, 1221–1223~1976!.



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76DEV/TOW Devaquet, A. J. P., Townshend, R. E., Hehre, W. J., ‘‘Conformational studies of 1,3-dienes,’’ J. Am.Soc.98, 4068–4076~1976!.

77VON Von Niessen, W., ‘‘Trans- andcis-glyoxal: A Green’s function calculation on their photoelectron spectrJ. Am. Chem. Soc.99, 7151–7153~1977!.

78COS/FRA Cossart-Magos, C., Frad, A., Tramer, A., ‘‘Fluorescence and phosphorescence spectra of glyoxal-h2 and -d2

from single vibronic levels of1Au and3Au states,’’ Spectrochim. Acta A34, 195 ~1978!78LUC/SCH Lucchese, R. R., Schaefer, H. F., III, ‘‘Formulation of the direct configuration interaction method for

spin states. Application to glyoxal,’’ J. Chem. Phys.68, 769–774~1978!.78PAR/ROR Parmenter, C. S., Rordorf, B. F., ‘‘Fluorescence from selected rotational levels ofS1 glyoxal,’’ Chem. Phys.

27, 1–9 ~1978!.79MOR/MAK Morozov, A. A., Makhnev, A. S., Panchenko, Y. N., Stepanov, N. F., ‘‘Calculation of some mole

parameters of glyoxal,’’ Vestn. Mosk. Univ., Ser. 2: Khim.20, 326–331~1979!.81NGU/TRO Nguyen-Xuan, T., Tronchet, J. M. J., Bill, H., ‘‘Conformational equilibriums of carbohydrates on the

of sC(sp2),C(sp3) bonding. IX. Study of the factors affecting the conformational equilibrium ofE-1,3-disubstituted propenes using energy partitioning techniques,’’ Helv. Chim. Acta64, 1949–1958~1981!.

81OSA/SHA Osamura, Y., Shaefer, H. F. III, Dupuis, M., Lester, W. A., Jr., ‘‘A unimolecular reaction ABC→A1B1Cinvolving three product molecules and a single transition state. Photodissociation of glyHCO—HCO→H21CO1CO,’’ J. Chem. Phys.75, 5828–5836~1981!.

82BOC/TRA Bock, C. W., Trachtman, M., George, P., ‘‘Anab initio study of the geometry of the C—C~H!vO group, thef C—C2 stretching force constant, and thef CvO,C—C coupling constant in conjugated monosubstituted carbocompounds,’’ Chem. Phys.68, 143–154~1982!.

83PAN/MOC Panchenko, Y. N., Mochalov, V. I., Pentin, Y. A., ‘‘Calculation of potential curves of the internal rotatioglyoxal and its fluoro derivatives in the CNDO/2 approximation taking into account a change in geomVestn. Mosk. Univ., Ser. 2: Khim.24, 357–360~1983!.

85MUS/FIG Musso, G. F., Figari, G., Magnasco, V., ‘‘Improved bond-orbital calculations of rotation barriers inecules containing conjugated double bonds and/orp lone pairs,’’ J. Chem. Soc., Faraday Trans. 281,1243–1258~1985!.

86DUV/KIN Duval, A. B., King, D. A., Haines, R., Isenor, N. R., Orr, B. J., ‘‘Coherent Raman spectroscopy of glyvapor,’’ J. Raman Spectrosc.17, 177–182~1986!.

86SPA/PRA Spangler, L. H., Pratt, D. W., Birss, F. W., ‘‘Rotational analysis of some vibronic bands in the3Au21Ag

transition of glyoxal. Spin splittings in the lowest triplet state of the isolated molecule,’’ J. Chem. Phy85,3229–3236~1986!.

86YAM/YAM Yamanouchi, K., Yamada, H., Tsuchiya, S., ‘‘Rotationally resolved stimulated emission pumping specglyoxal cooled in supersonic free jet,’’ Chem. Phys. Lett.132, 361–364~1986!.

87PEB/JOS Pebay Peyroula, E., Jost, R., ‘‘S1←S0 laser excitation spectra of glyoxal in a supersonic jet: Vibratioanalysis,’’ J. Mol. Spectrosc.121, 177–188~1987!.

87ROD/OLD Rodler, M., Oldani, M., Grassi, G., Bauder, A., ‘‘Rotational spectra of s-trans and s-cis glyoxal-d1

(CHO—CDO) observed by microwave Fourier transform spectroscopy,’’ J. Chem. Phys.87, 5365–5369~1987!.

88FAB Fabian, W. M. F., ‘‘AM1 calculations of rotation around essential single bonds and preferred conformin conjugated molecules,’’ J. Comput. Chem.9, 369–377~1988!.

89BRI Brinn, I. M., ‘‘Fundamental vibrational frequency correlation. IV.C2v2C2h in-plane trends,’’ SpectrochimActa A 45, 653–659~1989!.

89MOH/PAY Mohan, S., Payami, F., Kuttiappan, P., ‘‘Laser Raman spectrum of glyoxal and its vibrational anaProc. Indian Natl. Sci. Acad. A55, 598–601~1989!.

92WIB/RAB Wiberg, K. B., Rablen, P. R., Marquez, M., ‘‘Resonance interactions in acyclic systems. 5. Structures,distributions, and energies of some hetrobutadiene rotamers,’’ J. Am. Chem. Soc.114, 8654–8668~1992!.

95MO/ZHA Mo, Y., Zhang, Q., ‘‘Why N2O2 is cis while (CHO)2 is trans: MO and VB studies,’’ Int. J. Quantum Chem56, 19–26~1995!.

96PRO/SHO Promyslov, V. M., Shorygin, P. P., ‘‘Quantum-chemical study of conjugation in molecules contconjugated CvC and CvO bonds,’’ Izv. Akad. Nauk, Ser. Khim. 1648–1652~1996!.

97REM/WAT Rempe, S. B., Watts, R. O., ‘‘The convergence properties of hindered rotor energy levels,’’ ChemLett. 269, 455–463~1997!.

14.6. Extended Bibliography for Cyanooxomethyl Radical, NC 2O

91GUR/VEY Gurvich, L. V., Veyts, I. V., Alcock, C. B.,Thermodynamic Properties of Individual Substances, 4th ed.~Hemisphere, New York, 1991!, Vol. 2.



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92DOR/GUR Dorofeeva, O. V., Gurvich, L. V., ‘‘Thermodynamic properties of linear carbon chain moleculesconjugated triple bonds. Part 2. Free radicals CnH (n52 – 12) and CnN (n52 – 11),’’ Thermochim. Acta197, 53–68~1992!.

94PED Pedley, J. B.,Thermochemical Data and Structures of Organic Compounds~Thermodynamics ResearcCenter, College Station, TX, 1994!, Vol. I.

14.7. Extended Bibliography for Oxalic Acid, C 2H2O4

26VER/HAR Verkade, P. E., Hartman, H., Coops, J., ‘‘Calorimetric researches. X. Heats of combustion of sucterms of homologous series: Dicarboxylic acids of the oxalic acid series,’’ Recl. Trav. Chim.45, 373–393~1926!.

78DEV/NOV De Villepin, J., Novak, A., Romain, F., ‘‘Vibrational spectra of oxalic acids. II. IR and Raman spectra oa-phase of oxalic acid, and its deuterium and oxygen-18 derivatives,’’ Spectrochim. Acta A34, 1019–1024~1978!.

80SHI Shippey, T. A., ‘‘Vibrational studies in aqueous solutions. Part I. The oxalate ion,’’ J. Mol. Struct.65, 61–70~1980!.

95CHE/CHE Chen, L.-T., Chen, G.-J., Fu, X.-Y., ‘‘Theoretical studies on the mechanism of the thermal decarboxand decarbonylation of a number ofa-ketoacids,’’ Chin. J. Chem.13, 487–492~1995!.

14.8. Extended Bibliography for Methyl Hydroperoxide, CH 4O2

79MOL/ARG Molina, M. J., Arguello, G., ‘‘Ultraviolet absorption spectrum of methyl hydroperoxide vapor,’’ GeopRes. Lett.6, 953–955~1979!.

96GRE/COL Grela, M. A., Colussi, A. J., ‘‘Quantitative structure-stability relationships for oxides and peroxidpotential atmospheric significance,’’ J. Phys. Chem.100, 10150–10158~1996!.

96JUR/MAR Jursic, B. S., Martin, R. M., ‘‘Calculation of bond dissociation energies for oxygen containing molecuab initio and density functional theory methods,’’ Int. J. Quantum Chem.59, 495–501~1996!.

97JAC/WEH Jacob, P., Wehling, B., Hill, W., Klockow, D., ‘‘Feasibility study of Raman spectroscopy as a toinvestigate the liquid-phase chemistry of aliphatic organic peroxides,’’ Appl. Spectrosc.51, 74–80~1997!.

14.9. Extended Bibliography for Dimethyl Peroxide, C 2H6O2

82BAT/WAL Batt, L., Walsh, R., ‘‘A reexamination of the pyrolysis of bis trifluoromethyl peroxide,’’ Int. J. Chem. Kin14, 933–944~1982!.

92ZYA/KNY Zyatkov, I. P., Knyazhevich, N. D., Gogolinskii, V. I., Pitsevich, G. A., ‘‘Quantum-chemical calculationsstructure and conformations of organosilicon peroxides,’’ Vestn. Beloruss. Gos. Univ., Ser. 1, No. 2,~1992!.

96LEE/SHI Lee, S.-Y., Shin, Y.-J., ‘‘Estimation of thermodynamic properties in the pyrolysis of dialkyl peroxidhelium gas,’’ Hwahak Konghak34, 592–596~1996!.

14.10. Extended Bibliography for Diacetyl Peroxide, C 4H6O4

71VLE/MIJ Vledder, H. J., Mijlhoff, F. C., Leyte, J. C., Romers, C., ‘‘Electron diffraction investigation of the molecstructure of gaseous acetic anhydride,’’ J. Mol. Struct.7, 421–429~1971!.

80HOL/GUN Hollenstein, H., Gu¨nthard, H. H., ‘‘A transferable valence force field for polyatomic molecules. A schefor a series of molecules containing carbon:oxygen groups,’’ J. Mol. Spectrosc.84, 457–477~1980!.

81VAN/VAN Van Eijck, B. P., van Opheusden, J., van Schaik, M. M. M., van Zoeren, E., ‘‘Acetic acid: Microwspectra, internal rotation and substitution structure,’’ J. Mol. Spectrosc.86, 465–479~1981!.

93CHE/ALL Chen, K., Allinger, N. L., ‘‘A molecular mechanics study of alkyl peroxides,’’ J. Comput. Chem.14,755–768~1993!.

94BEN/TAD Benassi, R., Taddei, F., ‘‘Conformational properties of peroxyacids, peroxyesters and structurallyradicals: A theoreticalab initio MO approach,’’ J. Mol. Struct.: THEOCHEM303, 83–100~1994!.

96JON Jonsson, M., ‘‘Thermochemical properties of peroxides and peroxyl radicals,’’ J. Phys. Chem.100, 6814–6818 ~1996!.



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bromoacetic acid

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