Classical tosylate/chloride leaving group approach supports a tetrahedral transition state for additions to trigonal carbon.

Trends in organic chemistry Pub Date : 2018-01-01
Malcolm J D'Souza, Jeremy Wirick, Jasbir Deol, Dennis N Kevill
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Abstract

The experimentally measured rates of solvolysis of 2-chloroethoxycarbonyl chloride (2-chloroethyl chloroformate, 3), 2-chloroethoxycarbonyl p-toluenesufonate (5), and phenoxycarbonyl p-toluenesulfonate (6) were followed at 25.0 °C in various pure and binary aqueous-organic solvents with varying degrees of polarity. An analysis of the rate constants for 3, 5, and 6, was carried out using the two-term extended Grunwald-Winstein equation and comparisons are made to the previously published results for ethyl and phenyl chloroformate esters. The k OTS/k Cl rate ratios and the Grunwald-Winstein l/m ratios indicate the probability of a dominant bimolecular carbonyl-addition pathway in the more nucleophilic solvents. Nevertheless in 3 and 5, in the strongly hydrogen-bonding 70% and 50% HFIP mixtures, a side-by-side ionization mechanism is favored.

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经典的甲苯磺酸酯/氯化物离去基团方法支持添加到三角碳的四面体过渡态。
在25.0°C下,在不同极性的各种纯和二元水性有机溶剂中,对2-氯乙氧基羰基氯(2-氯甲酸乙酯,3)、2-氯甲氧基羰基对甲苯磺酸酯(5)和苯氧羰基对甲苯磺酸盐(6)的溶剂解率进行了实验测量。使用两项扩展的Grunwald-Winstein方程对3、5和6的速率常数进行分析,并将其与先前发表的氯甲酸乙酯和苯基酯的结果进行比较。k OTS/k Cl速率比和Grunwald-Winstein l/m比表明在更亲核的溶剂中存在占主导地位的双分子羰基加成途径的可能性。然而,在3和5中,在强氢键的70%和50%的HFIP混合物中,并排电离机制是有利的。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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