A Comparison of the Ab Initio Calculated and Experimental Conformational Energies of Alkyl Cyclohexanes

Authors

Fillmore Freeman, University of California at IrvineFollow
Zufan M. Tsegai, Wavefunction, Inc.
Marc Kasner, Montclair State University
Warren J. Hehre, University of California at Irvine

Document Type

Article

Publication Date

5-1-2000

Journal / Book Title

Journal of Chemical Education

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.

DOI

10.1021/ed077p661

Montclair State University Digital Commons Citation

Freeman, Fillmore; Tsegai, Zufan M.; Kasner, Marc; and Hehre, Warren J., "A Comparison of the Ab Initio Calculated and Experimental Conformational Energies of Alkyl Cyclohexanes" (2000). Department of Chemistry and Biochemistry Faculty Scholarship and Creative Works. 542.
https://digitalcommons.montclair.edu/chem-biochem-facpubs/542