取代苯甲醛肟和取代苯乙酮肟电化学氧化机理的研究

Studies on the Electrochemical Oxidation of Substituted Benzaldehyde and Acetophenone Oximes

研究了10种取代苯甲醛肟和5种取代苯乙酮肟的电化学氧化机理.这二类肟的氧化电位随取代基吸电子能力的增大而增高,并与它们相应的Hammett常数有线性关系.它们在电化学氧化过程中均有iminoxy自由基生成,但最后产物各不相同.用控制电位电解和紫外吸收光谱检测法验证了部分电化学氧化产物、因此,电化学氧化法可作为由肟类产生iminoxy自由基的一种方法.

The electrochemical oxidation of 10 substituted benzaldoximes and 5 substituted ace-tophenone oximes has been studied. The results indicate that the benzaldoximes are first oxidized to iminoxy radicals and then transformed via chemical coupling of the radicals to the dehy-drodimers adsorping on the electrode, it appears to be an irreversible reaction and absorptive process. The acetophenone oximes are also oxidized to iminoxy radicals, but the dehydrodimers formed by radical coupling rapidly decompose to the ketone and other products, diffusing easily to the medium, it appears to be a reversible electrode reaction and an irreveribly adsorptive process. The products of electrochemical oxidation of benzaldehyde and acetophenone oximes have been confirmed by controlled potential electrolysis and UV-spectrophotometry. For both the monosubstituted benzaldehyde and acetophonone oximes there exists a linear relationship between the oxidative potentials and the Hammett constants of the substituents. The oxidative potential increases with increasing electrowithdrawing power of the substituent. The electrochemical oxidation can be used for generating iminoxy radicals from oximes.