Molecular structures and intramolecular interactions in dimethyl cyclohexane isomers

Abstract

AbstractThe geometries of ten isomers of dimethyl cyclohexane were determined by ab initio gradient geometry refinement with the 4‐21G basis set. It is found that many intramolecular interactions are clearly manifested by correlated structural trends, and that they are consistent with strain energies calculated by employing previously defined ab initio group equivalents. Specifically, non‐bonded interactions are found between two adjacent methyl groups in some of the forms, and between axial methyl groups and adjacent axial CH bonds in others. Unperturbed axial CH and CC bonds are consistently longer than equatorial bonds. In general, CH bonds which are involved in non‐bonded repulsive interactions are shortened, i.e., strengthened, and the corresponding HCC angles are large, compared to non‐interacting parameters.