用循环伏安法研究醌亚胺的脱氨反应

CYCLOVOLTAMMETRIC STUDIES ON THE DEAMINATION OF N-SUBSTITUTED QUINONE-IMINES

用循环伏安法研究了N,N-二乙基对苯二胺,N,N,N′,N′-四乙基对苯二胺,N,N-二乙基氨基酚三类化合物的电化学氧化及其氧化产物的后继化学反应,求算了脱氨反应速率常数,揭示了苯环上甲基取代基和氮原子上不同取代基对脱氨反应的影响。 脱氨反应为OH^-或水进攻醌亚胺的亲核反应。由于甲基的斥电子效应,当苯环上引进甲基取代基时,环上负电荷增大,带正电荷的醌亚胺趋于稳定,水解反应速度减慢。 苯环上引进二个甲基取代基,其相应的苯胺化合物的半波电位下降大约120mV。二乙基对苯二胺的苯环上每引进一个甲基取代基,其氧化产物与彩色成色剂偶合生成的染料的吸收峰向长波方向移动20—30nm。

The kinetics and mechanism of the deamination of N-substimted quinonediimines and N-substituted quinone monoimines were examined as a function of increasing pH. In this work, the rate constants of the deamination were determined with a semiempirical procedure of stationary electrode polarography.Deamination is initiated by nucleophilic attack on the most positively charged carbon atom of the benzene ring. Therefore, electron donating substituent has an effect on the rates of deamination and half-wave potential. Under the same condition, the half-wave potential of 2-methyl substituted compound is ca. 120 mV lower than the unsubstituted one. The absorption maximum of the dye formed by a methyl-substituted quinonediimine with the coupler would shift about 20-30 nm to the longer wavelength when compared with the unsubstituted compound.