Ab Initio calculations relevant to the mechanism of chemical carcinogenesis by N-nitrosamines. Part 7. The nitrosation of amines by nitrosyl chloride

Ab Initio molecular orbital calculations using split-valence 3-21G and 4-31G basis sets are reported on the formation of ONCl from HONO and HCl and on the formation of H₂NNO from NH₃ and ONCl. Both minima and transition structures were fully optimized. The energy barriers for both reactions are low, due in part to the flat nature of the potential-energy surfaces, showing that the reactions proceed readily. The calculations show that both reactions may proceed via a low-energy closed shell mechanism without the explicit involvement of water molecules in the transition structure. The calculations also identify the structural features involved in the saddle points for both reactions.