N—H bond dissociation energies in N,N′-diphenyl-1,4-phenylenediamine and its aminyl radical

Abstract

The N—H bond dissociation energy (D _NH) in the 4-anilinodiphenylaminyl radical formed from N,N′-diphenyl-1,4-phenylenediamine was experimentally determined and calculated by the quantum-chemical method. The experimental D _NH value was found from the enthalpy of the reaction of N,N′-diphenyl-1,4-benzoquinonediimine with 4-hydroxydiphenylamine taking into account the bond dissociation energies in 4-hydroxydiphenylamine and its aminyl and phenoxyl radicals, which were determined by the intersecting parabolas method from the kinetic data. The quantum-chemical calculations of D _NH used several semiempirical methods by the MOPAC program and the ab initio and DFT methods by the GAUSSIAN 94/98 program. The D _NH values, which were closest to the experimental values, were obtained by the B3LYP/6-31+G* method. The results of quantum-chemical calculations of the N—H and O—H bond dissociation energies in 4-hydroxydiphenylamine and its radicals are presented.