AB-INITIO CALCULATIONS OF THE STRUCTURE AND INVERSION BARRIERS OF CHLORAMIDE, H2NCL, AND N-CHLORO-N-METHYLMETHANAMINE, (CH3)(2)NCL

The ab initio geometries of the equilibrium forms and transition state s of the amino nitrogen inversion for H2NCl and (CH3)(2)NCl were calcu lated by the RHF and MP2 methods with the use of the 6-31G, 6-31G**, and 6-311G* basis sets. The inclusion of electron correlation at the MP2 level increases the barrier height estimates and yields a somewhat better agreement between the calculated and experimental geometric pa rameters. The obtained data do not agree with the idea that a larger i nversion barrier is associated with a more pyramidal configuration of the nitrogen atom Methyl substituents flatten the nitrogen configurati on in (CH3)(2)NCl. The barrier heights calculated by the MP2 method ar e 10.2 kcal mol(-1) for H2NCl and 12.6 kcal mol(-1) for (CH3)(2)NCl, o r 9.3(1.0) and 12.0 (1.0) kcal mol(-1), respectively, when zero-point corrections are made. (C) 1997 Elsevier Science B.V.