Quantum-chemical ab initio calculations of the enthalpies of formation and hydrogenation of imines

Quantum-chemical ab initio calculations of the structure and total energy of several aliphatic and aromatic imines and amines were performed. The method of isodesmic reactions with group balance and the G2MP2 procedure were used to calculate the enthalpies of formation (Delta(f)Hdegrees) of these compounds and the enthalpies of hydrogenation (Delta(hydr)Hdegrees) of imines. The additivity rule for Delta(f)Hdegrees within the framework of the Benson method was shown to hold, and group contributions to the enthalpies of formation of nitrogen derivatives of various structures were determined. The replacement of H atoms in H2C=NH by the Me, Et, Pr, i-Pr, Ph, and CH2=CH radicals was found to consistently change Delta(hydr)Hdegrees. Corrections for substitution were determined, which allowed the enthalpies of hydrogenation of imines of various structures to be calculated with high accuracy.