Theoretical studies on the formation of N-nitrosodimethylamine

The mechanisms of the formation of N-nitrosodimethylamine (NDMA) were studied at the MP2/6-311+G(d,p)//B3LYP/6-311+G(d,p) level of theory. We focused on the formation of NDMA from the reactions of dimethylamine (DMA) with nitrous acid and nitrite anion. Our calculations show that the reaction of DMA with nitrous acid is predicted to proceed via two distinct pathways: a concerted or a stepwise mechanism. Moreover, the energy barrier for the stepwise mechanism is somewhat higher than that for the concerted mechanism. The difference in these barriers indicates that the reaction of DMA with nitrous acid via the concerted mechanism is much more favored than that via the stepwise mechanism. In the other situation, our results demonstrate that the reaction of DMA with nitrite anion becomes feasible in the presence of carbon dioxide. Furthermore, this reaction proceeds via a stepwise pathway, in which CO₂ first attacks DMA, the result of which then reacts with nitrite anion. It is noteworthy that carbon dioxide appears to be an active catalyst to promote the formation of NDMA. Additionally, the effects of aqueous solvation on the reactions of DMA with nitrous acid and nitrite anion were investigated.