Change of the favored routes of EI MS fragmentation when proceeding from N1, N1-dimethyl-N2-arylformamidines to 1,1,3,3-tetraalkyl-2-arylguanidines: substituent effects
作者:Ewa D. Raczyńska、Mariusz Makowski、Jean-François Gal、Pierre-Charles Maria
DOI:10.1002/jms.1766
日期:——
ormamidines and of 1,1,3,3‐tetraalkyl‐2‐arylguanidines are structurally analogous and similar electron‐ionization mass spectral fragmentation may be expected, they display important differences in the favored routes of fragmentation and consequently in substituent effects on ion abundances. In the case of formamidines, the cyclization‐elimination process (initiated by nucleophilic attack of the N‐amino
尽管N 1,N 1-二甲基N 2-芳基甲am和1,1,3,3-四烷基-2-芳基胍的系列在结构上相似,并且可能会出现类似的电离质谱碎片,但它们在有利的裂解途径,从而对离子丰度产生取代基效应。就甲am而言,环化消除过程(由苯环的2-位上的N-氨基原子的亲核攻击引发)和环状苯并咪唑鎓[M-H] +离子的形成占主导,而损失NR 2该组更优选胍。为了获得有关主要片段最可能结构的信息,对选定的一组进行了量子化学计算。线性对数之间关系的良好我[M-H] +我[M] +• }和σ - [R +在取代基常数对在苯环位置仅用于甲脒(发生- [R = 0.989)。在胍的情况下,这种关系并不重要(r = 0.659)。在log I [M‐NMe 2 ] + / I [M] +• }与σ之间发现良好的线性关系p +常数(r = 0.993)。版权所有©2010 John Wiley&Sons,Ltd.