THE MOLECULAR-STRUCTURE AND PSEUDOROTATIONAL MOTION OF TRANS-1,2-DIMETHYLCYCLOPENTANE AS DETERMINED BY GAS-PHASE ELECTRON-DIFFRACTION

The molecular structure and conformational composition of trans-1,2-dimethylcyclopentane have been studied at nozzle temperatures of 298 K and 448 K by gas-phase electron diffraction. The molecule is found to be pseudorotating with a flat minimum at the diequatorial form. The enthalpy difference between the diaxial and the diequatorial forms is found to be about 1.9 kcal mol-1. Least squares analysis of the pseudorotational model results in the following bond distances (r(g)) and valence angles (angle-alpha): r(C-H) = 1.099(6) angstrom, r(C-C) = 1.540(2) angstrom, angle CCC = 115(1)-degrees, angle CCH = 114(1)-degrees, angle CC(m)H = 108(2)-degrees and q = 0.33(3) angstrom.