氮氧自由基研究 ⅩⅪ.水溶液中哌啶氮氧自由基单电子还原反应机理的极谱研究  

Studies on Nitroxides ⅩⅪ. The Mechanism for the One-Electron Reduction Electrode Reaction of Piperidine Nitroxides in Aqueous Solution Studied by Polarography

作　　者：张发[1] 刘有成[1] 

机构地区：[1]兰州大学化学系

出　　处：《化学学报》1989年第11期1120-1122,共3页Acta Chimica Sinica

摘　　要：氮氧自由基在电极上可得到电子而被还原，但关于哌啶氮氧自由基在水溶液中的电极还原反应，仅Neiman等用经曲极谱法考察过其半波还原电位与介质pH的关系，认为自由基被还原为相应的羟胺，质子参与电极反 ，但未能确定质子化过程是先于还是后于电子转移过程。The experimental results obtained from sampled d. c. polarography (SDCP), normal pulse polarography (NPP), differential pulse polarography (DPP) and a. c. polarography (ACP) with 2, 2, 6, 6-tetramethyl-4-hydroxypiperidinyl-1-oxy (1), 2, 2, 6, 6-tetramethyl-4-oxopiperidinyl-1-oxy (2) and 2, 2, 6, 6-tetramethyl-piperidinyl- 1-oxy (3) in aqueous solution showed that these nitroxides can be reduced on the electrode with the formation of the corresponding hydroxylamines as their products. The half-wave potentials and the peak potentials increased with the decrease of the pH of the medium. A linear relationship between the peak potentials of ACP of the nitroxides and the pH of the medium has been found with the slope of -0.03 V/pH.The ratio between the total limiting current of NPP and that of SDCP are independent of the pH of the medium and the nitroxides studied. A heterogeneous electron transfer followed by protonation in homogeneous medium (EC) is proposed for the reductive process studied.

关 键 词：水溶液 哌啶氮氧自由基 单电子还原反应 反应机理 极谱 

分 类 号：O621.146[理学—有机化学] O657.14[理学—化学]