Molecular structures of dinitroanilines and trinitroanilines

The molecular structures of six positional dinitroaniline isomers and six positional trinitroaniline isomers were calculated by a density functional theory of the Becke's three-parameter hybrid (B3LYP) method with 6-31G* basis set. Calculations found that deformations of the phenyl ring and distortions of the nitro and amino groups with the phenyl ring of each isomer were different. Deformations of the phenyl ring do not completely match the rule predicted by Domenicano and co-workers. Except for the inductive and resonance effects, the steric effects also play an influential role in the deformation of the phenyl ring and the distortion of the substitution groups with the ring. Calculated energies indicated that for dinitroanilines, 2,4-dinitroaniline and 2,6-dinitroaniline are the favored molecules while 2,3-dinitroaniline and 3,4-dinitroaniline are the unfavored ones; for trinitroanilines, 2,4,6-trinitroaniline is the most favored molecule and 3,4,5-trinitroaniline is the most unfavored one, For some isomers having an intramolecular hydrogen bonds as the C-NO...HN-C type, it is generally stronger than nitrotoluene isomers which have the C-NO...HC-C type of intramolecular hydrogen bonds. (C) 1994 Elsevier Science Ltd. All rights reserved.