Carboxylates as proton-accepting groups in concerted proton-electron transfers.: Electrochemistry of the 2,5-dicarboxylate 1,4-hydrobenzoquinone/2,5-dicarboxy 1,4-benzoquinone couple
Carboxylates as proton-accepting groups in concerted proton-electron transfers.: Electrochemistry of the 2,5-dicarboxylate 1,4-hydrobenzoquinone/2,5-dicarboxy 1,4-benzoquinone couple
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DOI：
10.1021/ja0621750
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发表时间：
2006-07-12
影响因子：
15
通讯作者：
Saveant, Jean-Michel
中科院分区：
文献类型：
--
作者：
Costentin, Cyrille;Robert, Marc;Saveant, Jean-Michel
协同质子和电子转移（CPET）目前吸引了相当大的理论和实验的关注，特别是在考虑到它们可能参与许多酶促反应。通过在非水介质中对2，5-二羧基1，4-苯醌/2，5-二羧基1，4-羟基苯醌对进行循环伏安研究，探讨了羧酸根基团作为质子接受位点在CPET反应中的作用。羧酸基团邻位的酚基团的存在下，诱导去除一个电子耦合的酚质子转移到羧酸氧。电化学反应的动力学和观察到的显著的氢/氘动力学同位素效应明确地表明，电子转移和质子转移是协同的，从而提供了羧酸基团作为协同质子-电子转移反应中质子接受位点的作用的额外证明。
Concerted proton and electron transfers (CPET) currently attract considerable theoretical and experimental attention, notably in view of their likely involvement in many enzymatic reactions. The role of carboxylate groups as proton-accepting sites in CPET reactions is explored by means of a cyclic voltammetric investigation of the 2,5-dicarboxy 1,4-benzoquinone/2,5-dicarboxylate 1,4-hydrobenzoquinone couple in a nonaqueous medium. The presence of carboxylate groups ortho to the phenol groups induces the removal of an electron to be coupled with the transfer of the phenolic proton to a carboxylate oxygen. The kinetics of the electrochemical reaction and the observation of a significant hydrogen/deuterium kinetic isotope effect unambiguously indicate that electron transfer and proton transfer are concerted, thus providing an additional demonstration of the role of carboxylate groups as proton-accepting sites in concerted proton−electron transfer reactions.