【摘要】 利用紫外光谱方法测定了维生素A及其乙酸酯在不同胶束水溶液中的衰变速率常数和衰变活化参数.数据显示,维生素A及其乙酸酯在阴离子胶束溶液SDS中的衰变速度要远大于在阳离子胶束溶液CTAB和中性胶束溶液TX-100中的衰变速度.机理分析表明,维生素A及其乙酸酯在水溶液中的衰变是经过先质子化,再脱去一分子水或乙酸生成碳正离子中间体,碳正离子再脱去质子,经重排后得到最终产物脱水维生素A.更多还原

【Abstract】 The decay of retinol(vitamin A)and retinyl acetate was studied by kinetic measurements in various aqueous micellar solutions.The first-order rate constants were obtained at different temperatures,and from which the corresponding activation parameters were derived.The results show that the decay of retinol and retinyl acetate are much faster in anionic micelles(SDS)than that in cationic micelles(CTAB)and neutral micelles(TX-100),which indicate that the decay is carried out by the protonation of retinol or retinyl acetate first,then one molecular water or acetic acid is lost to produce the carbonium ion,which release the proton followed to generate the anhydroretinol.And the rate constants of the decay of retinol and retinyl acetate show strong dependence on pH,which indicate that,the protonation of retinol or retinyl acetate is the rate-determining step.更多还原