N－和对位取代苯胺及其正离子基在二甲亚砜溶液中的酸性解离常数

Acidities of α-and para-Substituted Anilines and of the Corresponding Radical Cations in DMSO Solution

本文报道了在ＤＭＳＯ中测定的Ｎ－取代苯胺和对位取代乙酰苯胺的酸性解离常数［ｐＫａ（ＨＡ）］。利用热力学循环原理，通过对ｐＫａ和中性分子及其共轭碱的氧化电位的测定，求得了用直接方法难以得到的正离子基的酸性解离常数［ｐＫａ（ＨＡ（＋·））］，并对所得的ｐＫａ（ＨＡ）和ｐＫａ（ＨＡ（＋·））的取代基效应进行了讨论。

Acidities of the α- and para-substituted anilines and their radical cations were determined respectively by an accurate spectrophotometric titration and by a thermochemical evaluation. The simple method used in estimating the acidities of radical cations involves combining the equilibrium acidities of the parent acids(HA) in DMSO with the oxidation potentials of the neutral molecules,E(ox)(HA), and of their conjugate bases,E(ox)(A-), defined from a thermodynamic cycle. The results were discussed in terms of the substituent effects.