作者:R. Venkatesh、K. Karunakaran
DOI:10.14233/ajchem.2014.15506
日期:——
The kinetics of oxidation of 9 meta- and 15 para- substituted aromatic anils by sodium perborate were investigated in aqueous acetic acid medium. The reaction was second order with respect to aromatic anil and first order with respect to the sodium perborate. The increase of [H+] in this oxidation retards the rate of the reaction. The observed rate constant for the substituents were plotted against the Hammett constant, s and a non-linear concave downward curve was obtained for the anils with substituents in the aniline moiety. The observed break in the log kobs versus s was attributed to the transition state whereas the non-linear concave upward curve was observed for the substituents in the benzaldehyde moiety and a non-linear concave upward curve was observed for the substituents in the combination of aniline and benzaldehyde moiety. The electron withdrawing substituents fall on one side of the curve, having a negative r value and the electron releasing substituents fall on the other side, with a positive r value and a suitable mechanism was proposed.
在水性醋酸介质中,研究了9个间位和15个对位取代的芳香胺由过硼酸钠氧化的动力学。该反应对芳香胺呈二级动力学,对过硼酸钠呈一级动力学。在此氧化反应中,[H+]的增加会减慢反应速率。对于取代基,观察到的速率常数与Hammett常数s的关系绘制成图,结果呈现出非线性向下凹的曲线,适用于取代在苯胺部分的胺类。log k_obs与s的关系中观察到的断裂归因于过渡态,而针对取代在苯甲醛部分则观察到非线性向上凹的曲线,在苯胺和苯甲醛组合部分的取代基也观察到了非线性向上凹的曲线。电子吸引取代基位于曲线的一侧,具有负的r值,而电子释放取代基位于曲线的另一侧,具有正的r值,并提出了一种适当的机制。