Microwave Studies of Glycerol

F.J. Lovas, and D.F Plusquellic

NIST

and

V.V. Ilyushin and R.A. Motiyenko

Institute of Radio Astronomy of NASU

Outline

Background on Studies of Polyols (for astronomy)

MW Study of Glycerol:ab Initio calculations

Prior free jet study (60 - 78 GHz)

FTMW study (9 - 26.5 GHz)

Summary

Glycerol: CH2OHCHOHCH2OH

Sweet, colorless, viscous liquid

Results from hydrolysis of fats & oils

Many applications:pharmaceuticals & cosmetics

chemical stabilizer

plasticizer coatings

moisturizer

adhesives & lubricants

Sugars and Polyols in Space

C2 sugar: “Interstellar Glycolaldehyde: The First Sugar” J.M. Hollis, F.J. Lovas, & P.R. Jewell, Ap. J. 540, L107 (2000)“Green Bank Telescope Observation of Glycolaldehyde”Hollis, Jewell, Lovas & Remijan, ApJ 613, L45 (2004)

C2 sugar alcohol: “Interstellar Antifreeze: Ethylene Glycol” Hollis, Lovas, Jewell, & Coudert, Ap. J. 571, L59 (2002)

“Ethylene glycol in comet C/1995 O1 (Hale-Bopp)” Crovisier, et al. Astron. Astrophys. 418, L35 (2004).

C3 sugars: “GBT Detection of New Interstellar Aldehydes: Propenal andPropanal” Hollis, Jewell, Lovas, Remijan & Møllendal, Ap. J.610, L21 (2004). Negative result on glyceraldehyde, C3H6O3

Sugars and Polyols in Space

C3 sugars: “1,3-Dihydroxyacetone in Sgr B2(N-LMH): The First Interstellar Ketose” S.L. Widicus Weaver & G.A. BlakeAp. J. 624, L33 (2005); erratum Ap. J. 632, Li63 (2005)

“Investigating the Limits of Chemical Complexity in Sagittarius B2(N): A Rigorous Attempt to confirm 1,3-dihydroxyacetone” Apponi, Halfen, Ziurys, Hollis, Remijan & Lovas Ap. J. 643, L29 (2006)

63 new transitions of DHA were sought but noplausible emission was observed for 97% of these

Murchison and Murray Meteorite Studies

Polyols in Meteorites by GC-MS

Carbonaceous meteorites as a source of sugar-related organic compounds for the early Earth“ Cooper, Kimmich, Belisle, Sarinana, Brabham & Garrel, Nature 414, 879 (2001).

“Murchison meteorite is generally used as the standard reference for organic compounds in Extraterrestrial material.”

Carbons Sugars Sugar Alcohols Sugar Acids

C2 --- ethylene glycol ----

C3 dihydroxyacetone glycerol glyceric acid

C4 --- Erythritol &Threitol

erythronic acid &threonic acid

C5 --- ribitol & isomers

ribonic acid &isomers

Prior Lab and Theoretical Studies

Ab Initio study of ethylene glycol and glycerol:Teppen et al. J. Mol. Struct. 314, 169 (1994).

Found 11 stable conformers for glycerol

“Free jet investigation of the rotational spectrum of glycerol” G. Maccaferri, W. Caminati, & P.G. Favero, J. Chem. Soc. FaradayTrans. 93, 4115 (1997).

Identified the 2 lowest energy conformers in the 60 – 78 GHz rangefor the normal and tri-OD species

(1) G'Gg'gg' E = 0.0 cm-1

(2) GGtg'g' E = 34.4 cm-1

(3) GGgg'g' E = 207.6 cm-1

(4) G'Gg'gt E = 240.4 cm-1

(5) GG'tg'gE = 245.9 cm-1

Five lowest energy conformers of glycerol and their relative energies from ab initio MP2 aug-cc-pVTZ basis set with zero point corrections

NIST

Mini-FTMW

Spectrometer

O p tica l Tech n o lo g y D iv is io n

Mirror-MountedHeated Reservoir Nozzle

9000 10000 11000 12000 13000 14000 15000 16000 17000 180002

3

4

5

6

7

8

9

10

Glycerol

Frequency (MHz)

Inte

nsit

y

A1

A1

A1

A1

A1A1

A2

A2

A2

A2

A2

A2

A2

A2Conformer 1

Conformer 2

Conformer 5a-type

*

*

*

C1C1

C1

B1 B1B2

B2

Parameter G'Gg'gg' (1)ab initio

MP2GGtg'g' (2)

ab initio MP2

Another Conformer like

(2)?

A (MHz) 4297.81022(11) 4327.5 0.7% 6258.33735(19) 6307.9 0.8% 6255.3793(13)

B (MHz) 3165.445328(94) 3206.1 1.3% 2283.292415(96) 2306.4 1.0% 2266.82639(79)

C (MHz) 2540.440776(96) 2583.4 1.7% 2015.899871(84) 2042.1 1.3% 2002.27853(76)

ΔJ (kHz) 1.4863(18) 0.5251(10) 0.5004(80)

Δ JK (kHz) 1.5133(52) 0.1784(32) 0.172(35)

Δ K (kHz) 2.8869(42) 7.520(16) 7.97(28)

δ J (kHz) 0.34223(93) 0.03254(34) 0.0367(45)

δ K (kHz) 0.9786(57) -0.649(14) -0.97(35)

Nlines 145 136 27

rms (MHz) 0.059 0.051 0.0022

Energy (cm-1) 0.0 34.4

Two Lowest Energy Conformers of Glycerol

C1 C1

Parameter GGgg'g' (3) ab initio MP2

A (MHz) 6224.6024(16) 6265.16 0.3%

B (MHz) 2270.72466(40) 2292.16 0.9%

C (MHz) 2011.66540(46) 2038.19 1.3%

Δ J (kHz) 0.5208(44)

Δ JK (kHz) 0.138(26)

Δ K (kHz) 8.02(37)

δ J (kHz) 0.0303(17)

δ K (kHz) -0.48(14)

Nlines 30

rms (MHz) 0.0034

Energy (cm-1) 207.6

New Conformer (3) at 207 cm-1

C1

ParameterGG'tg'g (5)

v=0GG'tg'g (5)

v=1ab initio MP2

A (MHz) 8208.24389(28) 8208.24979(28) 8295.01 1.0%

B (MHz) 1986.495283(71) 1986.495966(72) 2003.02 0.3%

C (MHz) 1712.662887(76) 1712.659143(75) 1728.10 0.9%

Δ J (kHz) 0.18335(74) 0.18249(74)

Δ JK (kHz) 2.4295(34) 2.4354(32)

Δ K (kHz) 8.406(38) 8.415(38)

δJ (kHz) 0.02318(16) 0.02363(16)

δ K (kHz) 1.146(11) 1.109(12)

E (MHz) 41.9254

Nlines 180 180

rms (MHz) 0.0025 0.0025

Energy (cm-1) 245.9

C1

Second New Conformer at 246 cm-1 with OH Tunneling

Measured and calculated dipole moments for glycerol conformers

G'Gg'gg' (1) Measured MP2 Diff. %

μa 0.780(6) D -0.81 D 3.8

μb 0.30(2) D 0.30 D 0.0

μc 1.134(4) D 1.25 D 10.2

GGtgg' (2) Measured MP2 Diff. %

μa 1.749(3) D -1.86 D 6.3

μb 0.901(2) D -1.04 D 15.5

μc 0.161(2) D -0.13 D 18.7

GGgg'g' (3) Measureda MP2 Diff. %

μa ≈1.7 D -1.61 D 5.3

μb ≈0.2 D -0.20 D 0.0

μc ≈1.7 D 2.22 D 30.3

a Estimated from intensity comparisons

GGtg'g (5) Measured MP2 Diff. %

μa 2.77(5) D -3.02 D 6.9

μb 1.47(7) D -1.20 D 18.4

μc ≈0. D 1.03 D ---

Summary

• FTMW spectrum yielded 4-5 conformers

• Ab initio calculations aided new conformer identification

• Dipole moments determined & aided assignments

• GBT data covered good candidate lines for conformers 1 & 2, but no signals observed down to 5 – 10 mK noise level