Ab Initio Structures for 90°-Twisted s-trans1,3-Butadiene and Cyclooctatetraene; the
Naked sp2-sp2 Bond and Other Disclosures
about Equilibrium Structures of Butadiene
David Feller, Department of Chemistry,
Washington State University, Pullman, WA 99164
Norman C. Craig and Albert R. Matlin,
Department of Chemistry and Biochemistry,
Oberlin College, Oberlin, OH 44074
Norm.Craig@oberlin.edu
Outline
• Structures of various 1,3-butadiene rotamers
from ab initio calculations.
• Lengths of the naked sp2-sp2 single bond and
the localized C=C bond.
• Comparison with the structure of
cyclooctatetraene from ab initio calculations.
• Comparison with the structure of a dimer of
butadiene ([4]-dendralene) from electron
diffraction.
trans
|
t.s. gau. t.s.(cis)
|
|
|
- trans. st ate (t-to-g) 24.8 kJ/mol
77°
- trans. st ate (cis) 16.5 kJ/mol
180°
- gauche 12.0 kJ/mol
142° (38°)
From analysis of the structure
in multiple transiti ons of the
torsional overtone in the gasphase Raman spectrum.
R. Engeln, D. Consalvo, J. Reuss, Chem. Phys. 1992, 160,
427-433.
See also J. R. Durig, W. E. Bucy, and A. R. H. Cole, Can.
J. Phys. 1975, 53, 1832-1837.
Method for ab initio Calculations
• CCSD(T)/aug-cc-pVnZ, n = 2,3,4. Frozen core.
• Complete basis set extrapolation of the
geometric parameters.
• Corrections for core/valence effects with
CCSD(T)/cc-pCVQZ applied to geometric
parameters.
• Corrections for scalar relativistic effects from
Douglas-Kroll-Hess CCSD(T)/cc-pVTZ_DK
calculations applied to geometric parameters.
Equilibrium (re) Structures for Butadiene
r(C=C)/Å
r(C–C)/Å
r(C–Ha)/Å
r(C–H c)/Å
r(C–H t)/Å
(C=C–C)/Å
(C=C–Ha)/Å
(C=C–Hc)/Å
(C=C–Ht)/Å
a
trans-butadiene
90°-twisted
SemiCCSD(T) CCSD(T)
a
expt. Lit. extrapol.b extrapol.b
1.338
1.338
1.333c
1.454
1.455
1.482d
1.085
1.085
1.085
1.082
1.082
1.082
1.079
1.080
1.081
123.6
123.5
123.8
119.9
119.8
119.3
121.0
121.0
120.2
121.5
121.5
121.2
N. C. Craig; P. Groner; D. C. McKean, J. Phys. Chem. A
2006, 110, 7461.
b
D. Feller, N. C. Craig, A. R. Matlin, J. Phys. Chem. A 2008,
112, 2131-2133. c Compare with ethylene, re = 1.330 Å.
d
Compare with an sp2-sp2 single bond of 1.470 Å estimated
from near-equilibrium structures of ethane and propene.
Rotamers of 1,3-Butadiene
ab initio
trans
r(C1=C2)/Å
r(C2-C3)/Å
(C1C2C3)/deg
(C1C2C3C4)/deg
E/kJ/mol
1.338
1.454
123.6
0
0
Transition
State (t-to-g)
1.333
1.483
123.8
78.3
26.0
90°twisted
1.333
1.482
123.8
90.0
25.5
gauche
Transition
State (cis)
1.336
1.468
124.4
144.5(35.5) 180.0
12.1
Experimentala
(C1C2C3C4)/deg 0
0
E/kJ/mol
a
77
24.8
90
23.1
142(38)
180.0
b
12.0/12.2 16.5
From evaluating the potential function reported by R. Engeln, D. Consalvo, J. Reuss,
Chem. Phys. 1992, 160, 427-433.
b
rH° from analysis of the temperature dependence of the UV spectrum by J. Saltiel, D.
F. Sears Jr., A. M. Turek J. Phys. Chem. A 2001, 105, 7569-7578.
90°-twisted butadiene
Boat form of cyclooctatetraene
[4]Dendralene
Dimer of 1,3-Butadiene
Dihedral angle = 71.7°; r(C3-C4) = 1.497 Å (long).a
Compare sp2-sp3 bond length in propene = 1.496 Å.b
a Electron
diffraction: P. T. Brain, B. A. Smart, H. E. Robertson, D. W. H.
Rankin, W. J. Henry, I. Gosney, J. Org. Chem. 1997, 62, 2767-2773.
b Equil. struct.: J. Demaison, H. D. Rudolph, J. Mol. Spectrosc. 2008, 248, 66-76.
Funding
National Science Foundation (Beowulf
cluster supercomputer)
Dreyfus Foundation
Department of Chemistry and Biochemistry,
Oberlin College
Additional Geometric Parameters
for [4]-Dendralenea
r(C1=C2)/Å
1.349(1)
r(C2-C3)/Å
1.478(2)
r(C3=C7)/Å
1.346(1)
124.4(3)
(C1C2C3)/deg
(123.2)
 (C2C3C7)/deg
117.6(7)
 (C4C3C7)/deg
119.2(5)
 (C2C3C4)/deg
-174.8(28)
 (C1C2C3C7)/deg
a
Electron diffraction: P. T. Brain, B. A.
Smart, H. E. Robertson, D. W. H. Rankin,
W. J. Henry, I. Gosney, J. Org. Chem. 1997,
62, 2767-2773
Comparison of re Structures of
Butadiene and Propene