Influence of the 1,1,3,3-tetramethylguanidinyl substituent on the charge distribution in chlorobenzenes, studied by35Cl NQR
作者:Boleslaw Nogaj、Przemyslaw Pruszyński
DOI:10.1002/mrc.1260250405
日期:1987.4
35Cl NQR measurements were carried out on a series of chlorobenzenes with the 1,1,3,3-tetramethylguanidinyl substituent TMG = –N=C[N(CH3)2]2}. The substituent constants σp, σm, σaI, and σR for the TMG group were estimated from the relationships between the NQR resonance frequencies, νQ, and substituent constant values, σ. The νQ value for 2-(4-chlorophenyl)-1,1,3,3-tetramethylguanidine is the lowest observed for all chlorobenzenes, and arises from the strong positive conjugative effect of the TMG group. This effect is attributed to the possible resonance stabilization of the positive charge. Steric inhibition of resonance is observed for the ortho-substituted isomers.
对一系列具有 1,1,3,3- 四甲基胍基取代基 TMG = -N=C[N(CH3)2]2} 的氯苯进行了 35Cl NQR 测量。TMG 基团的取代基常数 σp、σm、σaI 和 σR 是根据 NQR 共振频率 νQ 和取代基常数 σ 之间的关系估算的。在所有氯苯中,2-(4-氯苯基)-1,1,3,3-四甲基胍的 νQ 值最低,这是因为 TMG 基团具有强烈的正共轭效应。这种效应可归因于正电荷的共振稳定。在正交取代异构体中观察到了共振的立体抑制作用。