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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Kinetics and mechanisms of the unimolecular elimination of 2,2-diethoxypropane and 1,1-diethoxycyclohexane in the gas phase: Experimental and theoretical study
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Kinetics and mechanisms of the unimolecular elimination of 2,2-diethoxypropane and 1,1-diethoxycyclohexane in the gas phase: Experimental and theoretical study

机译：气相中2,2-二乙氧基丙烷和1,1-二乙氧基环己烷单分子消除的动力学和机理：实验和理论研究

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摘要

The gas-phase thermal elimination of 2,2-diethoxypropane was found to give ethanol, acetone, and ethylene, while 1,1-diethoxycyclohexane yielded 1-ethoxycyclohexene and ethanol. The kinetics determinations were carried out, with the reaction vessels deactivated with allyl bromide, and the presence of the free radical suppressor cyclohexene and toluene. Temperature and pressure ranges were 240.1-358.3 °C and 38-102 Torr. The elimination reactions are homogeneous, unimolecular, and follow a first-order rate law. The rate coefficients are given by the following Arrhenius equations: for 2,2-diethoxypropane, log k _1 (s ~(-1)) = (13.04 ± 0.07) - (186.6 ± 0.8) kJ mol ~(-1) (2.303RT) ~(-1); for the intermediate 2-ethoxypropene, log k _1 (s~(-1)) = (13.36 ± 0.33) - (188.8 ± 3.4) kJ mol ~(-1) (2.303RT) ~(-1); and for 1,1-diethoxycyclohexane, log k = (14.02 ± 0.11) - (176.6 ± 1.1) kJ mol -1 (2.303RT) -1. Theoretical calculations of these reactions using DFT methods B3LYP, MPW1PW91, and PBEPBE, with 6-31G(d,p) and 6-31++G(d,p) basis set, demonstrated that the elimination of 2,2-diethoxypropane and 1,1-diethoxycyclohexane proceeds through a concerted nonsynchronous four-membered cyclic transition state type of mechanism. The rate-determining factor in these reactions is the elongation of the C-O bond. The intermediate product of 2,2-diethoxypropane elimination, that is, 2-ethoxypropene, further decomposes through a concerted cyclic six-membered cyclic transition state mechanism.
机译：发现气相热消除2，2-二乙氧基丙烷得到乙醇，丙酮和乙烯，而1，1-二乙氧基环己烷产生1-乙氧基环己烯和乙醇。进行动力学测定，其中用烯丙基溴使反应容器失活，并存在自由基抑制剂环己烯和甲苯。温度和压力范围是240.1-358.3°C和38-102 Torr。消除反应是均匀的，单分子的，并且遵循一阶速率定律。速率系数由以下Arrhenius方程给出：对于2,2-二乙氧基丙烷，log k _1（s〜（-1））=（13.04±0.07）-（186.6±0.8）kJ mol〜（-1）（2.303 RT）〜（-1）;对于中间体2-乙氧基丙烯，log k _1（s〜（-1））=（13.36±0.33）-（188.8±3.4）kJ mol〜（-1）（2.303RT）〜（-1）;对于1,1-二乙氧基环己烷，log k =（14.02±0.11）-（176.6±1.1）kJ mol -1（2.303RT）-1。使用DFT方法B3LYP，MPW1PW91和PBEPBE，6-31G（d，p）和6-31 ++ G（d，p）基集对这些反应的理论计算表明，消除了2,2-二乙氧基丙烷和1,1-二乙氧基环己烷通过协调的非同步四元环过渡态类型的机理进行。这些反应中的决定速率的因素是C-O键的伸长率。 2，2-二乙氧基丙烷消除的中间产物，即2-乙氧基丙烯，通过一致的环状六元环状过渡态机理进一步分解。

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