p-硝基氯苯与α氰基乙酸乙酯-α-碳负离子的电子转移反应动力学研究: 非链式的自由基机理

在p-硝基氯苯(1)与α-氰基乙酰乙酯-α-碳负离子(2)的反应过程中, 测得了反应中间体p-硝基氯苯负离子自由基(3)的ESR谱。用ESR场/频联锁技术测定了(3)的ESR吸收强度-时间曲线, 当[1]《[2]时, 其结果与连续一级反应动力学相吻合。测得了从2向1的电子转移和3的分解反应速率常数和活化参数, 反应产物为α-氰基-α-(p-硝基苯基)乙酸乙酯和微量的硝基苯。为该反应提出了非链式的电子转移-负离子自由基分解-自由基偶合机理。

Studies on the kinetics of SET reaction of p-nitrochlorobenzene with ethylα-cyanoacetate-α-carbanion

The ESR spectrum of p-nitrochlorobenzene anion radical (I) resulting from single electron transfer (SET) reaction of p-nitrochlorobenzene (II) with Na+-CH(CN)CO2Et (III) in DMSO has been recorded at various temps. by means of ESR F/F lock technique. It was found that when II ?III, the reaction gave the kinetic expression for successive first-order reaction. The rate constants and the activation parameters for the SET reaction from III to II and the decomposition of I were determine The products were found to consist of chiefly Et a-cyano-a-(p-nitrophenyl)acetate and minute amount of nitrobenzene. A non-chain radical mechanism of aromatic nucleophilic substitution is proposed.