Effect of Cetyltrimethylammonium Micelles with Bromide, Chloride, and Hydroxide Counterions on the Rates of Decomposition of Para-Substituted Aryl-2,2,2-trichloroethanols in Aqueous NaOH
Effect of Cetyltrimethylammonium Micelles with Bromide, Chloride, and Hydroxide Counterions on the Rates of Decomposition of Para-Substituted Aryl-2,2,2-trichloroethanols in Aqueous NaOH
复制标题
具有溴离子、氯离子和氢氧化物抗衡离子的十六烷基三甲基铵胶束对 NaOH 水溶液中对位取代的芳基-2,2,2-三氯乙醇分解速率的影响
DOI：
10.1021/j100027a031
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
L. Romsted
中科院分区：
文献类型：
--
作者：
Maria Angelica Bonadiman Marin;F. Nome;D. Zanette;Cesar Zucco;L. Romsted
研究了十六烷基三甲基铵胶束与溴离子、氯离子和氢氧根离子（CTAX， X= Br, Cl， OH）对芳基2,2,2 -三氯乙醇分解的影响。该反应遵循（Elcb） R型机理，即乙醇被oh快速可逆地去质子化，然后三氯甲基碳离子的速率决定损失生成苯甲醛产物。在表面活性剂的存在下，尽管在胶束相中醇氧离子的单分子分解速率常数km降低了3 - 5倍，但km对取代基效应的依赖（从CTABr、CTAC1和CTAOH的相应Hammett图中得到的值为- 0.49、-0.46和0.45）与在水中观察到的相似（= -0.5）。观察到的抑制作用可以从基态电荷稳定的角度来解释，即季铵离子与烷氧阴离子的相互作用比与三氯甲基碳离子的相互作用更强。
The effect of cetyltrimethylammonium micelles with bromide, chloride, and hydroxide counterions, CTAX, X= Br, Cl, OH, on the decomposition of aryl-2, 2, 2-trichloroethanols was determined. This reaction follows an (Elcb) R type mechanism, ie, rapid reversible deprotonation of the alcohol by OH-followed by rate determining loss of trichloromethylcarbanion to give the benzaldehyde product. In the presence of surfactants, despite the 3—5-fold decrease in the rate constant for the unimolecular decomposition of the alkoxide ion in the micellar phase, km, the dependence of km on substituents effects (values of of—0.49,—0.46, and—0.45 were obtained from the corresponding Hammett plots for CTABr, CTAC1, and CTAOH) is similar to that observed in water (=—0.5). The observed inhibition can be rationalized in terms of charge stabilization of the ground state, ie, quaternary ammonium ions interact more strongly with alkoxy anions than with trichloromethyl carbanions.