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A Comparison of the ab Initio Calculated and Experimental Conformational Energies of Alkylcyclohexanes
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Fillmore Freeman and Zufan M. Tsegai
Department of Chemistry, University of California, Irvine, Irvine, CA 92697-2025
Marc L. Kasner
Department of Chemistry and Biochemistry, Montclair State Univerity, Upper Montclair, NJ 07043
Warren J. Hehre
Department of Chemistry, University of California, Irvine, Irvine, CA 92697, and Wavefunction, Inc., Irvine CA 92612
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May 2000
Vol. 77 No. 5
p. 661
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| Abstract |
Ab initio 6-31G(d) and MP2/6-31G(d)//6-31G(d) methods were used to
calculate the energies of the rotamers of the chair conformers of
alkylcyclohexanes and trimethylsilylcyclohexane. The MP2/6-31G(d)//6-31G(d)
calculated conformational energies (
 or A values, in kcal/mol)
of the alkylcyclohexanes (Me = 1.96; Et = 1.80; Pr = 1.73 iso-Pr = 1.60;
t-Bu = 5.45; neo-pent = 1.32) and trimethylsilylcyclohexane
(SiMe3 = 2.69) are similar to the experimental values.
Plots of the calculated conformational energies for the alkylcyclohexanes
and trimethylsilylcyclohexane versus their experimental
values are
linear (slope = 1.253 and r = .993 for 6-31G(d) and slope = 1.114
and r = .982 for MP2/6-31G(d)//6-31G(d)). The conformational
energies are determined primarily by steric effects which include gauche
(synclinal) interactions and repulsive nonbonded interactions in both the
axial and equatorial conformers.
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| More Information |
 Citation |
Freeman, Fillmore; Tsegai, Zufan M.; Kasner, Marc L.; Hehre, Warren J. J. Chem. Educ. 2000 77 661.
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Keywords |
Computational Chemistry; Molecular Modeling / Dynamics; Organic Chemistry
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History |
Created:
Last Updated: |
March 31, 2000
April 15, 2005
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