Empirical force field calculations (MM2-V4) on biphenyl and 2,2′-bipyridine

Abstract

The experimental rotational barriers of biphenyl, 1, (6.0 and 6.5 kJ mol −1) and the ab initio calculated conformational behaviour of 2,2′-bipyridine, 2, (29.3, 21.7, 27.6 and 0.0 kJ mol −1), as well as their geometry, have been correctly reproduced by Empirical Force Field calculations using a modified MM2 program (MM2-V4) containing the fourth term in the torsional potential function ( 1: 5.52 and 6.60 kJ mol −1; 2: 29.7, 25.0, 26.9 and 0.0 kJ mol −1).