阳离子Gemini表面活性剂胶束对乙酸酯碱性水解的影响

Effects of cationic gemini surfactant micelles on the alkaline hydrolysis of acetic esters

在 25℃条件下,研究了乙酸乙酯、乙酸丁酯及乙酸戊酯在Gemini阳离子表面活性剂1, 2-双亚甲基-双(十六烷基二甲基溴化铵) (16-2-16)胶束溶液中的碱性水解反应。实验结果表明,乙酸乙酯、乙酸丁酯、乙酸戊酯在Gemini表面活性剂 16-2-16胶束溶液中的碱性水解反应速率,在低浓度条件下随表面活性剂浓度的增加呈上升趋势即催化作用,在一定浓度下达最大值,然后随表面活性剂浓度的增加呈下降趋势,最终在较高表面活性剂浓度下显示出对酯碱性水解的禁阻作用。此外,随乙酸酯疏水性的增加,Gemini表面活性剂胶束对其碱性水解的影响减小。

Effects of micelles of a gemini cationic surfactant,1,2-ethane bis(dimethyl cetyl ammonium bromide) (16-2-16),on the alkaline hydrolysis of three acetic esters, i.e. ethyl acetate, butyl acetate and pentyl acetate,have been studied at 25℃. It was found that apparent second-order rate constants of the alkaline hydrolyses of ethyl ester, pentyl acetate and butyl acetate increased at lower concentration of gemini cationic surfactant 16-2-16 and reached a maximum, then decreased with an increase in surfactant concentration. Further increases in surfactant concentration resulted in the inhibition of the alkaline hydrolysis of these three esters. In addition, the significance of the effect of the 16-2-16 micelles on alkaline hydrolysis of the acetic esters decreased with an increase in hydrophobicity of the substrate.