摘要
用MNDO法全优化了20多个Mannich反应中间体—N-羟甲基胺和亚甲胺碳正离子的平衡几何构型,计算了它们的电子结构。根据N-羟甲基胺脱水反应的能量变化(ΔE)、亚甲胺碳正离子的净电荷(Q_(σ+))和几何构型,分类讨论比较了N-羟甲胺脱水的难易、亚甲胺碳正离子的稳定性以及对反应历程的影响。以脲素、甲醛和硝仿之间的Mannich反应为例,建议在可多重N-羟甲基化情形下Mannich反应的机理。此外还对硝基脲的N-羟甲基胺及其亚甲胺碳正离子进行了计算研究。
The equilibrium geometries and electronic structures of more than twenty intermediates of Mannich reaction, N-hydroxymethyl amines and methylene amine carbenium ions, have been optimized and calculated by MNDO method. According to the energy change (ΔE) of elimination water of N-hydroxymethyl amine and the net charge (Q_(c^+)) on carbenium ion as well as the configurations obtained from calculations, we assess and explain the feasibility of elimination of water, the stability of methylent amine carbenium ion and the effect on mechanism of the would do Mannich reaction. The mechanism of Mannich reaction from OC(NH_2)_2, HCHO and HC(NO_2)_3 was suggested as a example in the case of multiple N-hydroxymethylation which would take place. The N-hydroxymethyl amines and corresponding methylene amine carbenium ions for nitrourea have been also calculated and discussed.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
1992年第1期67-71,共5页
Acta Chimica Sinica
