TOBAD - A METHOD FOR THE ESTIMATION OF TORSION BARRIERS FROM CRYSTAL-STRUCTURE DATA - CONFORMATIONAL-ANALYSIS OF N,N-DIMETHYLANILINE AND DERIVATIVES

A new method for the estimation of torsion barriers and its applicatio n to conformational analysis is presented. This method, the ToBaD meth od (method of the torsion barrier derivative), makes use of crystal st ructure data. It is based on the assumption that the conformation of a compound in the crystalline phase must be very close to a (local) min imum energy conformation of this compound in the gas phase. The ToBaD method is demonstrated for the rotation of the phenyl-N bond in N,N-di methylaniline. Two geometries of this compound are handled separately: one in which. the nitrogen substituents are in a pyramidal or sp(3) g eometry, and the other in which the nitrogen atom and its substituents are coplanar(the sp(2) geometry). It is predicted, by means of the To BaD method, that for both geometries the conformation in which the nit rogen lone pair or p orbital is perpendicular to the aromatic ring is the lowest energy conformation. (C) 1994 by John Wiley and Sons, Inc.