Isomerization of Neopentyl Chloride and Neopentyl Bromide by a 1,2-Interchange of a Halogen Atom and a Methyl Group
作者:Carmen E. Lisowski、Juliana R. Duncan、Anthony J. Ranieri、George L. Heard、D. W. Setser、Bert E. Holmes
DOI:10.1021/jp1047166
日期:2010.9.30
The observed unimolecular reactions, which give 2-methyl-2-butene and 2-methyl-1-butene plus HCl, as products, are explained by a mechanism that involves the interchange of a methyl group and the chlorine atom to yield 2-chloro-2-methylbutane, which subsequently eliminates hydrogen chloride by the usual four-centered mechanism to give the observed products. The interchange isomerization process is the
氯甲基和叔丁基在室温下的重组用于产生内部能量为89 kcal mol -1的新戊酰氯分子。所观察到的单分子反应会生成2-甲基-2-丁烯和2-甲基-1-丁烯加HCl,是通过涉及甲基和氯原子互换生成2-氯的机理来解释的。 -2-甲基丁烷,随后通过通常的四中心机理消除氯化氢,得到了所观察到的产物。交换异构化过程是限速步骤。用CD 2 Cl和C(CH 3)3进行了类似的实验自由基来测量动力学同位素效应,以帮助证实所提出的机制。在B3PW91 / 6-31G(d',p')水平上使用密度泛函理论来验证Cl / CH 3交换机理并表征交换跃迁状态。这些计算提供了分子的振动频率和惯性矩以及过渡态,用于评估统计的非分子速率常数。匹配计算的和实验的速率常数,得到62±2 kcal mol -1Cl原子与甲基交换的阈值能量。计算模型也用于重新解释新戊基氯和新戊基溴的热单分子反应。这些反应的先前假设的Wagner