praveenkumar boopalachandran, 1 jaan laane 1 and norman c. craig 2 1 department of chemistry, texas...
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Praveenkumar BoopalachandranPraveenkumar Boopalachandran,,11 Jaan Laane Jaan Laane 11 and and Norman C. Craig Norman C. Craig 22
1 1 Department of Chemistry, Texas A&M University, College Station, Texas 77840Department of Chemistry, Texas A&M University, College Station, Texas 77840 22 Department of Chemistry and Biochemistry, Oberlin College, Oberlin, Ohio 44074 Department of Chemistry and Biochemistry, Oberlin College, Oberlin, Ohio 44074
Gas Phase Raman Spectra of Gas Phase Raman Spectra of Butadiene and Butadiene-dButadiene and Butadiene-d66 and the and the
Internal Rotational Potential Energy Internal Rotational Potential Energy FunctionFunction
OutlineOutline
IntroductionIntroduction
Research Work Research Work
1,3-butadiene (-d1,3-butadiene (-d00))
1,3-butadiene (-d1,3-butadiene (-d66))
1,3-butadiene (-d1,3-butadiene (-d22))
1,3-butadiene (-d1,3-butadiene (-d44))
SummarySummary
1,3-butadiene1,3-butadiene
It is a planar molecule with CIt is a planar molecule with C2h2h symmetry and possesses a trans symmetry and possesses a trans geometry.geometry.
Earlier studies to establish the structure of the higher energy Earlier studies to establish the structure of the higher energy conformer gave contradictory results.conformer gave contradictory results.
Our goal is to determine an experimental torsional potential.Our goal is to determine an experimental torsional potential.
McKean, D. C.; Craig, N. C.; Panchenko, Y. N. J. Chem. Phys. 110 (2006) 8044
trans gauche cis
conformers of 1,3-butadieneconformers of 1,3-butadieneCH2=CHCH=CH2
Published Raman spectrum by Carreira Published Raman spectrum by Carreira
Published Raman spectrum of Carreira shows trans and cis conformers Published Raman spectrum of Carreira shows trans and cis conformers Carreira’s potential shows higher energy conformer to be cisCarreira’s potential shows higher energy conformer to be cis
L.A. Carreira, J. Chem. Phys. 62 (1975) 3851
Low-frequency Raman spectrum of 1,3- butadiene
0-2
1-3
2-4
3-5
4-6
5-7
6-87-9
limited data
Potential for the torsional vibration in 1,3-butadiene
trans cis
10
23 4
6 7
5
trans cis
Published Raman spectrum by EngelnPublished Raman spectrum by Engeln
Low-frequency Raman spectrum of 1,3- butadiene Potential for the torsional vibration in 1,3-butadiene
Engeln, R.; Consalvo, D.; Reuss, J. J. Chem. Phys. 160 (1992) 427
Published Raman spectrum of Engeln shows trans-gauche-gauche potential Published Raman spectrum of Engeln shows trans-gauche-gauche potential Engeln’s potential shows higher energy conformer to be gaucheEngeln’s potential shows higher energy conformer to be gauche
trans trans
gauche gauche
0-2
1-34-6
5-7
6-8
3-5
2-4
7-9
0--2-
0+-2+
1--3-
1--3-
1+-3+
cis
10
23 4
6 7
5
Published Calculated PotentialPublished Calculated Potential
trans
gauche gauche
trans
cis
100 200 3000
500
1000
1500
2000
V (
cm-1)
Torsional angle (degrees)Torsional angle (degrees)Torsional angle (degrees)
V (
cm-1)
Feller, D.; Craig, N. C. J. Phys. Chem. 2009, 113, 1601Karpfen, A.; Vudhichai, P. J. Mol. Phys. 102 (2004) 819
Theoretical calculations show the higher energy conformer to be gaucheTheoretical calculations show the higher energy conformer to be gauche
Plotted Karpfen’s potentialPlotted Karpfen’s potential Feller’s potentialFeller’s potential
OutlineOutline
IntroductionIntroduction
Research Work Research Work
1,3-butadiene (-d1,3-butadiene (-d00))
1,3-butadiene (-d1,3-butadiene (-d66))
1,3-butadiene (-d1,3-butadiene (-d22))
1,3-butadiene (-d1,3-butadiene (-d44))
SummarySummary
Raman instrumentRaman instrumentRaman spectrometer
sample compartment
heatable vapor cell
Vapor Raman spectrum of 1,3-butadiene (bottom) compared to Vapor Raman spectrum of 1,3-butadiene (bottom) compared to the calculated DFT spectrum (top)the calculated DFT spectrum (top)
cm-1
vapor
1600 1200 800 400
ν4
ν12ν13ν16
ν18
1600 1200 800 400
ν4
ν12
ν13ν16
ν18
calculated
good agreement with each other
Low-frequency Raman spectrum of 1,3-butadiene (-dLow-frequency Raman spectrum of 1,3-butadiene (-d00))
320 300 280 260 240 220 320 300 280 260 240 220
The transition observed at 214.9 cmThe transition observed at 214.9 cm-1 -1 cannot be fitted with the Carreira potentialcannot be fitted with the Carreira potential
With this observation, we could fit a better torsional potential which is expected to be similar With this observation, we could fit a better torsional potential which is expected to be similar to Engeln’s trans-gauche-gauche potentialto Engeln’s trans-gauche-gauche potential
0-2
1-3
2-4
4-6
5-7
6-83-5
1+-3+
2-4
4-6
5-7
7-9
0--2-
0+-2+
1--3-
cm-1
280 260 240 220 200 180
0-2
4-6
1-3
2-4
6-8
3-5
5-7
7-9
0-2 transition:0-2 transition:322.4 cm322.4 cm-1-1 for d for d00
Drop in the frequency Mass Effect
Low-frequency Raman spectrum of 1,3-butadiene (-dLow-frequency Raman spectrum of 1,3-butadiene (-d66))
cm-1
320 310 300 290 280 270 260 250 320 310 300 290 280 270 260 250
Low-frequency Raman spectrum of 1,3-butadiene (-dLow-frequency Raman spectrum of 1,3-butadiene (-d22))
cm-1
0-2
1-36-8
3-52-4
4-6
5-7
7-9
Low-frequency Raman spectrum of 1,3-butadiene (-dLow-frequency Raman spectrum of 1,3-butadiene (-d44))
300 280 260 240 220 200 300 280 260 240 220 200
cm-1
0-21-3
6-83-5
2-44-6
5-7
7-9
Potential functions for the torsional vibration in 1,3-butadienePotential functions for the torsional vibration in 1,3-butadiene
Our new potential is similar to Engeln’s potentialOur new potential is similar to Engeln’s potentialEngeln, R.; Consalvo, D.; Reuss, J. J. Chem. Phys. 160 (1992) 427
Torsional Angle(degrees)
0 100 200 300
v(cm
-1)
0
500
1000
1500
2000
2500
trans trans
gauche gauche
cis
0
2
5
34
67891011
0+1+2+
3+4+
5+
1
0-1-2-3-4-5-
Observed and Calculated Raman Transitions (cmObserved and Calculated Raman Transitions (cm-1-1) for the ) for the Internal Rotation of 1,3-ButadieneInternal Rotation of 1,3-Butadiene
V1 = 469.2 cm-1; V2 = 1245.7 cm-1; V3 = 904.5 cm-1; V4 = 174.0 cm-1; V6 = 21.9 cm-1 B = 2.803 cm-1; V = ½ Σ Vn(1 cos n φ )
Transition Observed Calculateda Δ trans 1-2 (IR) 161.7 161.8 0.1
0-2 322.4 321.7 0.7 1-3 317.3 317.5 0.2 2-4 311.9 312.6 0.7 3-5 306.4 306.9 0.5 4-6 300.4 300.4 0.0 5-7 293.6 293.2 0.4 6-8 286.3 285.7 0.6
gauche 0 + 2 + 261.9 261.2 0.7 0 2 270.8 270.8 0.0 1 3 255.3 255.8 0.5 1 + 3 + 214.9 215.0 0.1
0
500
1000
1500
2000
2500
0 50 100 150 200 250 300 350
Torsional Angle (degrees)
ν(cm
-1)
Potential functions for the torsional vibration in 1,3-butadienePotential functions for the torsional vibration in 1,3-butadiene
Feller, D.; Craig, N. C. J. Phys. Chem. 2009, 113, 1601Karpfen, A.; Vudhichai, P. J. Mol. Phys. 102 (2004) 819
Feller
This work
Karpfen
Low-frequency Raman spectrum of 1,3-butadiene (heated @ 260 Low-frequency Raman spectrum of 1,3-butadiene (heated @ 260 ooC)C)
340 320 300 280 260 240 220
0-2
1-3
2-43-5
4-6
5-7
6-8
7-9
0--2-
0+-2+
1--3-
1+-3+
cm-1
Comparison of Low-frequency Raman spectrum of Comparison of Low-frequency Raman spectrum of 1,3-butadiene (RT and @ 260 1,3-butadiene (RT and @ 260 ooC)C)
320 300 280 260 240 220 cm-1
0-2
1-3
2-43-5
4-6
5-7
6-8
7-9
0--2-
0+-2+
1--3-
1+-3+
RTRT
260 260 00CC
Intensity ratio of Raman transition at room temperature and 260Intensity ratio of Raman transition at room temperature and 26000CC
Combination Bands (Combination Bands (νν1212+ + νν1313) of 1,3-butadiene) of 1,3-butadiene
680 670 660 650 680 670 660 650
cm-1
0-1
1-2 2-3
3-4
4-5 5-6
6-7
ν12+ ν13
1180 1170 1160 1150
cm-1
0-1
1-2
2-3
3-4
ν10+ ν13
Combination Bands (Combination Bands (νν1100+ + νν1313) of 1,3-butadiene) of 1,3-butadiene
Energy level diagram of 1,3-butadieneEnergy level diagram of 1,3-butadiene
OutlineOutline
IntroductionIntroduction
Research Work Research Work
1,3-butadiene (-d1,3-butadiene (-d00))
1,3-butadiene (-d1,3-butadiene (-d66))
1,3-butadiene (-d1,3-butadiene (-d22))
1,3-butadiene (-d1,3-butadiene (-d44))
SummarySummary
SummarySummary
Raman spectra of 1,3-butadiene and 1,3-butadiene (-dRaman spectra of 1,3-butadiene and 1,3-butadiene (-d66) have ) have been collected and the torsional vibration have been studied. been collected and the torsional vibration have been studied.
The torsional vibration confirms that the higher energy form has The torsional vibration confirms that the higher energy form has gauche conformation.gauche conformation.
The experimental and theoretical potential energy functions are The experimental and theoretical potential energy functions are reasonably in good agreement with each other. reasonably in good agreement with each other.
Future work would be carried out on other isotopic species and Future work would be carried out on other isotopic species and heated spectra.heated spectra.
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