Molecular mechanics (MM) and MM-EHMO conformational analysis of the diastereoisomers of 3-amino-1,2,3-triphenyl-1-propyl chloride

Abstract

The conformations of simple alkyl substituted 1,2-diphenylethanes and the diastereoisomers of 3-amino-1,2,3-triphenyl-1-propyl chloride were studied by the MM2 force field with the addition of electrostatic corrections to the aromatic force field as proposed recently by Allinger and Lii (dipole-dipole interactions) and independently by Pettersson and Liljefors (charge-charge interactions). Computations were also carried out with a modified version of the MM2 program utilizing the MM3 van der Waals potential function and parameters for C (type 2, sp2 hybridized) and H (type 5). The inclusion of dipole moments for the Csp2Csp3 and Csp2H bonds significantly improves the results. A lower value for the V1 parameter for the torsional unit CarCalCalCar had to be used instead of the MM2 value of 2.1 kcal/mol. Computations were carried out also with the hybrid MM-EHMO procedure. The latter method appears to work correctly also with 1,2,3-triphenylpropane systems.