Computational test for the performance of the improved MM2 aromatic force field

Abstract

The conformations of a set of compounds containing phenyl groups on neighbouring carbon atoms and polar substituants, including intramolecular hydrogen-bonded species, were studied using the molecular mechanics (MM2) force field with the addition of electrostatic corrections to the aromatic force field, as recently proposed by Allinger and Lii (dipole-dipole interactions). The inclusion of dipole moments for C sp 2 -C sp 3 and C sp 2 -H bonds significantly improves the results. However, lower value for the V 1 parameter for the torsional unit C sp 2 -C sp 3 - sp 3 -C sp 2 was used instead of the MM2 value (8.8 kJ mol −1). The computational scheme was used to analyse the hindered phenyl and formylmethylamino group rotations in the ul (1 R ∗, 2 S ∗, 3 S ∗) and 1u (1 R ∗, 2 R ∗, 3 S ∗) isomers of 3-(formylmethylamino)-1,2,3-triphenyl-1-propylchloride.