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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Unimolecular reactions of vibrationally excited CF2ClCHFCH3 and CF2ClCHFCD3: Evidence for the 1,2-FCl interchange pathway
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Unimolecular reactions of vibrationally excited CF2ClCHFCH3 and CF2ClCHFCD3: Evidence for the 1,2-FCl interchange pathway

机译：振动激发的CF2ClCHFCH3和CF2ClCHFCD3的单分子反应：1,2-FC1交换途径的证据

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摘要

Chemically activated CF2ClCHFCH3 and CF2ClCHFCD3 molecules were prepared with 94 kcal mol(-1) of vibrational energy by the recombination of CF2ClCHF and CH3(CD3) radicals at room temperature. The unimolecular reaction pathways were 2,3-FH(FD) elimination, 1,2-ClF interchange and 1,2-ClH elimination; the interchange produces CF3CHClCH3(CF3CHClCD3) with 105 kcal mol(-1) of vibrational energy. Rate constants for CF2ClCHFCH3 [CF2ClCHFCD3] were (3.1 +/- 0.4) x 10(6) s(-1) [(1.0 +/- 0.1) x 10(6) s(-1)] for 2,3-FH [FD] loss, (1.5 +/- 0.2) x 10(6) s(-1) [(8.3 +/- 0.9) x 10(5) s(-1)] for 1,2-ClF interchange, and (8.2 +/- 1.0) x 10(5) s(-1) [(5.3 +/- 0.6) x 10(5) s(-1)] for 1,2-ClH [DCl] loss. These correspond to branching fractions of 0.55 +/- 0.06 [0.43 +/- 0.04] for 2,3-FH [FD] loss, 0.29 +/- 0.03 [0.35 +/- 0.04] for 1,2-ClF interchange, and 0.16 +/- 0.02 [0.22 +/- 0.02] for 1,2-ClH [ClD] loss. Kinetic-isotope effects were 3.0 +/- 0.6 for 2,3-FH [FD] loss, 1.6 +/- 0.3 for 1,2-ClH loss, and 1.8 +/- 0.4 for 1,2-ClF interchange. The CF3CHClCH3 (CF3CHClCD3) molecules formed by 1,2-FCl interchange react by loss of HCl [DCl] with rate constants of (5.6 +/- 0.9) x 10(7) s(-1) [(2.1 +/- 0.4) x 10(7)] s(-1) for an isotope effect of 2.7 +/- 0.4. Density functional theory was employed to calculate vibrational frequencies and moments of inertia for the molecules and for the transition-state structures. These results were used with RRKM theory to assign threshold energies from comparison of computed and experimental unimolecular rate constants. The threshold energy for ClF interchange is 57.5 kcal mol(-1), and those for HF and HCl channels are 2-5 kcal mol(-1) higher. Experiments with vibrationally excited CF2ClCF2CF3, CF2ClCF2CF2Cl, and CF2ClCF2Cl, which did not show evidence for ClF interchange, also are reported.
机译：化学活化的CF2ClCHFCH3和CF2ClCHFCD3分子是通过在室温下将CF2ClCHF和CH3（CD3）自由基复合而以94 kcal mol（-1）的振动能制备的。单分子反应途径为2,3-FH（FD）消除，1,2-ClF交换和1,2-ClH消除。交换产生的CF3CHClCH3（CF3CHClCD3）具有105 kcal mol（-1）的振动能。对于2,3-FH，CF2ClCHFCH3 [CF2ClCHFCD3]的速率常数为（3.1 +/- 0.4）x 10（6）s（-1）[（1.0 +/- 0.1）x 10（6）s（-1）] [FD]损失，对于1,2-ClF交换，（1.5 +/- 0.2）x 10（6）s（-1）[（8.3 +/- 0.9）x 10（5）s（-1）]，以及对于1,2-ClH [DCl]损失，为（8.2 +/- 1.0）x 10（5）s（-1）[（5.3 +/- 0.6）x 10（5）s（-1）]。这些对应于2,3-FH [FD]损失的分支分数为0.55 +/- 0.06 [0.43 +/- 0.04]，对于1,2-ClF交换为0.29 +/- 0.03 [0.35 +/- 0.04]，以及对于1,2-ClH [ClD]损失为0.16 +/- 0.02 [0.22 +/- 0.02]。动力学同位素效应对于2,3-FH [FD]损失是3.0 +/- 0.6，对于1,2-ClH损失是1.6 +/- 0.3，对于1,2-ClF交换是1.8 +/- 0.4。通过1,2-FCl交换形成的CF3CHClCH3（CF3CHClCD3）分子通过速率常数为（5.6 +/- 0.9）x 10（7）s（-1）[[2.1 +/- 0.4 ）x 10（7）] s（-1）的同位素效应为2.7 +/- 0.4。密度泛函理论用于计算分子和过渡态结构的振动频率和惯性矩。这些结果与RRKM理论一起用于通过比较计算的和实验的单分子速率常数来分配阈值能量。 ClF交换的阈值能量为57.5 kcal mol（-1），而HF和HCl通道的阈值能量则高2-5 kcal mol（-1）。还报告了振动激发的CF2ClCF2CF3，CF2ClCF2CF2Cl和CF2ClCF2Cl的实验，这些实验没有显示ClF交换的证据。

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