二甲胺与亚硝酸反应生成N,N-二甲基亚硝胺的理论研究

应用量子化学计算方法在CCSD/6-311＋G(d,p)//B3LYP/6-311＋G(d,p)水平上对二甲胺(DMA)与亚硝酸作用形成N,N-二甲基亚硝胺(NDMA)的反应机理进行了研究. 分别讨论了DMA与一分子亚硝酸直接反应的途径和两分子亚硝酸先反应生成活性中间体N₂O₃再与DMA作用的间接反应途径. 计算结果表明, DMA与亚硝酸间接反应的活化能比直接反应的低约55 kJ/mol, 由此可推断DMA与亚硝酸生成NDMA的反应是以两分子的亚硝酸先生成ONNO₂再亚硝化DMA为主要反应途径. 这一结论和NDMA的形成速率与亚硝酸的浓度的平方成正比的实验结果相一致.

Theoretical Studies on the N-Nitrosodimethylamine Formation from Dimethylamine and Nitrous Acid

The mechanisms of N-nitrosodimethylamine(NDMA)formation from dimethylamine(DMA)and nitrous acid have been investigated at the CCSD/6-311 G(d,p)//B3LYP/6-311 G(d,p)level of the theory.Two different pathways have been taken into account.One was that one molecule of nitrous acid di-rectly reacted with DMA,and the other was that two molecules of nitrous acid reacted first to yield nitrogen trioxide,which then reacted with DMA.It was found that the energy barrier of the indirect reaction of DMA with nitrous acid was lower by around 55 kJ/mol than that of the direct pathway.Therefore,the indirect pathway,involving an active intermediate nitrogen trioxide,is the main pathway of NDMA formation.This conclusion is in good agreement with the experimental results in which the rate of NDMA formation is proportional to the square of the concentration of nitrous acid.