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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Unimolecular isomerization of CH_2FCD_2Cl via the interchange of Cl and F atoms: Assignment of the threshold energy to the 1,2-dyotropic rearrangement
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Unimolecular isomerization of CH_2FCD_2Cl via the interchange of Cl and F atoms: Assignment of the threshold energy to the 1,2-dyotropic rearrangement

机译：通过Cl和F原子的交换实现CH_2FCD_2Cl的单分子异构化：将阈值能量分配给1,2-双阳离子重排

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摘要

The room-temperature gas-phase recombination of CH_2F and CD _2Cl radicals was used to prepare CH_2FCD_2Cl molecules with 91 kcal mol~(-1) of vibrational energy. Three unimolecular processes are in competition with collisional deactivation of CH_2FCD_2Cl; HCl and DF elimination to give CHF=CD _2 and CH_2=CDCl plus isomerization to give CH _2ClCD_2F by the interchange of F and Cl atoms. The Cl/F interchange reaction was observed, and the rate constant was assigned from measurement of CHCl=CD_2 as a product, which is formed by HF elimination from CH_2ClCD_2F. These experiments plus previously published results from chemically activated CH_2ClCH _2F and electronic structure and RRKM calculations for the kinetic-isotope effects permit assignment of the three rate constants for CH_2FCD_2Cl (and for CH_2ClCD_2F). The product branching ratio for the interchange reaction versus elimination is 0.24 ± 0.04. Comparison of the experimental rate constant with the RRKM calculated rate constant permitted the assignment of a threshold energy of 62 ± 3 kcal mol-1 for this type-1 dyotropic rearrangement. On the basis of electronic structure calculations, the nature of the transition state for the rearrangement reaction is discussed. The radical recombination reactions in the chemical system also generate vibrationally excited CD _2ClCD_2Cl and CH_2FCH_2F molecules, and the rate constants for DCl and HF elimination were measured in order to confirm that the photolysis of CD_2ClI and (CH_2F)_2CO mixtures was giving reliable data for CH_2FCD_2Cl.
机译：利用室温的CH_2F和CD_2Cl自由基的气相复合法制备了具有91kcal mol〜（-1）振动能的CH_2FCD_2Cl分子。三个单分子过程与CH_2FCD_2Cl的碰撞失活竞争。去除HCl和DF，得到CHF = CD _2和CH_2 = CDCl，并且通过F和Cl原子的交换异构化得到CH _2ClCD_2F。观察到Cl / F交换反应，并且通过测量作为产物的CHCl = CD_2来指定速率常数，其是通过从CH_2ClCD_2F中HF消除而形成的。这些实验以及化学活化的CH_2ClCH_2F的先前发表的结果以及动力学同位素效应的电子结构和RRKM计算，可以分配CH_2FCD_2Cl（和CH_2ClCD_2F）的三个速率常数。交换反应与消除反应的产物支化比为0.24±0.04。将实验速率常数与RRKM计算出的速率常数进行比较，可以为这种1型致密重排指定阈值能量62±3 kcal mol-1。在电子结构计算的基础上，讨论了重排反应过渡态的性质。化学系统中的自由基重组反应还产生振动激发的CD _2ClCD_2Cl和CH_2FCH_2F分子，并测量了DCl和HF消除的速率常数，以确认CD_2ClI和（CH_2F）_2CO混合物的光解为CH_2FCD_2Cl提供了可靠的数据。

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