肉桂腈电化学还原反应机理

Electrochemical Reduction Reaction Mechanism of Cinnamonitrile

采用循环伏安法研究了肉桂腈在乙腈溶液中的电还原行为,其在-1.46和-2.0V处各存在一个还原峰.第一个峰处恒电位电解得到了线性、环化氢化二聚产物以及苯基戊二腈;第二个峰处电解得到了饱和二氢还原产物苯丙腈.结合循环伏安模拟判定了整个电还原的具体反应机理是肉桂腈通过电化学-电化学-化学-化学(EECC)反应机理生成苯丙腈,同时经历自由基-自由基(RR)过程得到线性和环化二聚产物,肉桂腈还可以与乙腈的共轭碱反应得到苯基戊二腈.最终通过循环伏安模拟求得相应反应的动力学常数,自由基-自由基耦合反应速率常数为104L·mol-.1s-1,第二个电子转移反应速率常数为0.3cm.s-1,其后质子化反应的速率常数为105s-1.

The electromduction of cinnamonitrile in MeCN solution was studied using cyclic voltammetry, with two reduction peaks at -1.46 and -2.0 V. Linear, cyclic hydrodimers, and 3-phenyl pentanedinitrile were synthesized at the first peak, while additional saturated hydro product was synthesized at the second peak. The reduction mechanism was proposed based on the experimental and cyclic voltammogram simulation results. Linear and cyclic hydrodimers were synthesized by a radical-radical （RR） route while a saturated hydro product was obtained via an electrochemical- eloctrochemical-chemical-chernical （EECC） process. 3-Phenyl pentanedinitrile was synthesized by the reaction of cinnamonitrile with the conjugate base of MeCN. Finally, the dynamic constants were calculated using cyclic voltammogram simulation. Result indicated that the rate constant of the RR reaction was found to be 10^4 L· mol^-1·s^-1, and the rate constant of the second electron transfer reaction was 0.3 cm·s^-1, while the rate constant of the subsequent proton reaction was 10^5 s^-1.