Electrophilic aromatic substitution. Part XVII. Protiodetritiation of some cycloalkyl- and secondary alkyl-benzenes. A linear free energy relationship for ortho-aromatic substitution
作者:M. M. Jean Le Guen、Roger Taylor
DOI:10.1039/p29760000559
日期:——
distribution in the Wheland intermediate. This correlation permits the first assignment of meaningful σ+ortho substituent constants for application to electrophilic substitutions of these compounds (but not their analogous side-chain reactions). Exchange at the ortho-positions of 1-ethylbutyl- and 1-ethylpropyl-benzene may be slightly hindered; exchange in these compounds was also accompanied by an intermolecular
根据三氟乙酸在70°下测得的某些环烷基和仲烷基苯(RPh)的电去铁酸酯化速率,可以确定邻位和对位取代的部分速率因子如下:(R =)环丁基,455 ,1,070;环戊基473,1 195:环己基406,886:1-甲基乙基,223,544; 1-甲基丙基,244,690:1-乙基丙基,196,682:1-乙基丁基,217,685。除后两种化合物外,每个烷基苯给出的常数log f o:log f p氢交换中大量其他芳香族化合物的比率为0.865±0.025;该比率是由Wheland中间体中的电荷分布精确预测的。这种相关性允许首先分配有意义的σ +邻位取代基常数,以应用于这些化合物的亲电子取代(但不允许其类似的侧链反应)。交易所在邻1-乙基丁基-苯和1-乙基丙基-苯的-位可能会稍微受阻;这些化合物之间的交换还伴随着分子间表面催化的烷基迁移,该迁移可能在空间上加速。讨论了环状取代基相对于其开链类似