Kinetics and mechanism of the aminolysis of aryl phenyldithioacetates in acetonitrile
Kinetics and mechanism of the aminolysis of aryl phenyldithioacetates in acetonitrile
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DOI：
10.1039/b002842h
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发表时间：
2001-03
期刊：
影响因子：
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通讯作者：
H. Oh;S. Kim;I. Cho;H. Lee;Ikchoon Lee
中科院分区：
文献类型：
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作者：
H. Oh;S. Kim;I. Cho;H. Lee;Ikchoon Lee
研究了Z-芳基苯基二硫代乙酸酯（C6 H5 CH 2C（S）SC 6 H4 Z）与苄胺（XC 6 H4 CH 2NH 2）在乙腈中于−25.0 °C下的氨解反应。基于（i）选择性参数βX（ρX）和βZ（ρZ）的大值，（ii）正的和大的交叉相互作用常数ρXZ（=2.05），以及（iii）遵守反应性-选择性原理，预测反应通过逐步机制进行，其中硫酚阴离子从两性离子四面体中间体T±中限速排出。氘代胺和低活化能（Δ H = 3 kcal mol−1）以及大的负活化熵（ΔS = −37至−53 e.u.）的显著正常动力学同位素效应（kH/kD = 1.14-1.81），与胺氢的同时质子转移与过渡态中离去基团的离去一致。
The aminolysis reactions of Z-aryl phenyldithioacetates (C6H5CH2C(S)SC6H4Z) with benzylamines (XC6H4CH2NH2) are investigated in acetonitrile at −25.0 °C. The reactions are predicted to proceed by a stepwise mechanism with rate-limiting expulsion of the thiophenolate anion from the zwitterionic tetrahedral intermediate, T±, based on (i) large magnitudes of selectivity parameters, βX (ρX) and βZ (ρZ), (ii) positive and large cross-interaction constants ρXZ (=2.05), and (iii) adherence to the reactivity–selectivity principle. The significant normal kinetic isotope effects (kH/kD = 1.14–1.81) involving deuterated amines and low activation enthalpies (ΔH‡ ≈ 3 kcal mol−1) together with large negative activation entropies (ΔS‡ = −37 to −53 e.u.) are consistent with concurrent proton transfer of amine hydrogen with the leaving group departure in the transition state.