CONFORMATIONAL-ANALYSIS OF ORTHO-SUBSTITUTED DIPHENYL ETHERS AND DIPHENYLMETHANES WITH LINEAR SUBSTITUENTS

Conformational analysis of di-ortho-substituted diphenylmethanes and d iphenyl ethers containing I, CCH, and CCCCH substituents was carried o ut by the molecular mechanics method using the MM3 program. Several mi nima on the potential energy surface, which correspond to the gg, gt, tg, and orf conformations, were found. An increase in the length of th e linear substituent results in a substantial decrease in the differen ce in the relative energies of conformers. Barriers to conformational transitions between the gt, tg, and orf conformers are less than 2 kca l 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 orf conformers are separated by a barrier of up to 6 kcal mol(-1) .