Conformational analysis of ortho-substituted diphenyl ethers and diphenylmethanes with linear substituents

Abstract

Conformational analysis of di-ortho-substituted diphenylmethanes and diphenyl ethers containing I, CCH, and CCCCH substituents was carried out by the molecular mechanics method using the MM3 program. Several minima on the potential energy surface, which correspond to the gg, gt, tg, and ort conformations, were found. An increase in the length of the linear substituent results in a substantial decrease in the difference in the relative energies of conformers. Barriers to conformational transitions between the gt, tg, and ort conformers are less than 2 kcal mol-1. The transition ort-gg requires expenditure of energy of up to 5 kcal mol-1. Two valleys of centrosymmetric pairs of the gt, tg, and ort conformers are separated by a barrier of up to 6 kcal mol-1.