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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Ethyl Cyclohexanone-2-carboxylate in Aqueous Micellar Solutions. 1. Ester Hydrolysis in Cationic and Nonionic Micelles
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Ethyl Cyclohexanone-2-carboxylate in Aqueous Micellar Solutions. 1. Ester Hydrolysis in Cationic and Nonionic Micelles

机译：胶束水溶液中的环己酮-2-羧酸乙酯。 1.阳离子和非离子胶束中的酯水解

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Hydrolysis rates for the ester of ethyl cyclohexanone-2-carboxylate (ECHC) were measured in aqueous dioxane mixtures and in aqueous micellar solutions of cationic, nonionic, and mixed cationic—nonionic detergents. The following cationic surfactants were used: dodecyltrimethylammonium bromide (DTABr), tetradecyl-trimethylammonium bromide (TTABr), tetradecyltrimethylammonium chloride (TTACl), tetradecyltrimethyl-ammonium acetate CITAAc), and cetyltrimethylammonium bromide (CTABr). Poly(ethylene oxide)-9-dodecyl ether (C_12E_9) and poly(ethylene oxide)-20-cetyl ether (C_16E_20) were used as the nonionic surfactants. The kinetic profiles of the reactions were investigated as a function of surfactant concentration. In aqueous strong mineral acid (HCI or HBr) solutions of the cationic surfactants DTABr, TTABr, TTAC1, and CTABr, the reaction was greatly inhibited at surfactant concentrations above the critical micelle concentration; the same behavior was observed for the influence of the nonionic surfactants and for the mixed surfactants DTABr + C12E9 analyzed in an equimolar mixture of both surfactants. Micellar effects were analyzed by means of the pseudophase mactel. When the hydrolysis reaction was studied in aqueous buffered solutions of acetic acid—acetate, the shape of the observed rate constant versus surfactant concentration (of TTACl and TIABr) profiles depended on surfactant concentration. At low surfactant concentration, first-order rate constants pass through maxima with increasing surfactant concentration followed by a gradual but steady decrease in the rate as the surfactant concawration increases further. By contrast, the first-order rate constant increases throughout the whole concentration range of TTAAc used. Micellar effects observed for the reaction in aqueous buffered solutions were analyzed qualitatively or quantitatively by means of the pseudophase ion exchange (PPIE) model. In every experimental situation, the reaction at the micellar interface is not negligible; however, the second—order constant in this region is lower than that measured in water.
机译：在水性二恶烷混合物和阳离子，非离子和阳离子-非离子混合洗涤剂的胶束水溶液中，测量了环己酮-2-羧酸乙酯（ECHC）的酯的水解速率。使用了以下阳离子表面活性剂：十二烷基三甲基溴化铵（DTABr），十四烷基三甲基溴化铵（TTABr），十四烷基三甲基氯化铵（TTACl），十四烷基三甲基醋酸铵CITAAc）和十六烷基三甲基溴化铵（CTABr）。聚（环氧乙烷）-9-十二烷基醚（C_12E_9）和聚（环氧乙烷）-20-十六烷基醚（C_16E_20）用作非离子表面活性剂。研究了反应的动力学曲线作为表面活性剂浓度的函数。在阳离子表面活性剂DTABr，TTABr，TTAC1和CTABr的强无机酸水溶液（HCI或HBr）中，在高于临界胶束浓度的表面活性剂浓度下，该反应被大大抑制。对于非离子表面活性剂的影响以及在两种表面活性剂的等摩尔混合物中分析的混合表面活性剂DTABr + C12E9，观察到相同的行为。胶束效应通过伪相位法分析。当在乙酸-乙酸盐的缓冲水溶液中研究水解反应时，观察到的速率常数与表面活性剂浓度（TTAC1和TIABr）的关系曲线的形状取决于表面活性剂浓度。在低表面活性剂浓度下，一阶速率常数随着表面活性剂浓度的增加而通过最大值，然后随着表面活性剂浓度的进一步增加而逐渐但稳定地降低。相反，在所使用的TTAAc的整个浓度范围内，一级速率常数增加。通过假相离子交换（PPIE）模型定性或定量地分析在缓冲水溶液中反应的胶束效应。在每种实验情况下，胶束界面的反应都是可以忽略的。但是，该区域的二阶常数低于水中测得的常数。

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