Rate parameters for the reactions of C/sub 2/H/sub 3/ and C/sub 4/H/sub 5/ with H/sub 2/ and C/sub 2/H/sub 2/
Rate parameters for the reactions of C/sub 2/H/sub 3/ and C/sub 4/H/sub 5/ with H/sub 2/ and C/sub 2/H/sub 2/
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DOI：
10.1021/j100325a019
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发表时间：
1988-07
期刊：
影响因子：
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通讯作者：
M. A. Weissman;S. Benson
中科院分区：
文献类型：
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作者：
M. A. Weissman;S. Benson
计算了C/sub 2/H/sub 3/和C/sub 4/H/sub 5/与H/sub 2/和C/sub 2/H/sub 2/反应的温度依赖性速率参数。使用Benson开发的过渡态理论估计方法来估计300 K，A（300）下的频率因子和活化热容。三角洲C/dagger//sub v/s，在300-1500 K的温度范围内。最近发表的实验测量的速率常数在300 K，k（300），与估计的A（300）一起使用，以获得在300 K的活化能，E（300）。那个...三角洲接下来使用C/dagger//sub v/'s来计算E（T）、A（T）和k（T）。k（T）值用修正的Arrhenius公式logk ' = logA' + nlogT-E '/2.3RT（n = /sub 300//sup 1500//R）再现良好。与H/sub 2/的反应具有较小的阿累尼乌斯图曲率。逆反应H + C/sub 2/H/sub 4/.. -->.. H/sub 2/ + C/sub 2/H/sub 3/，符合先前发表的高温数据。与C/sub 2/H/sub 2/的加成反应表现出明显的Arrhenius曲线曲率，正如对这些三电子三中心过渡态所预期的那样。活化能低于烷基自由基的类似反应，这与乙烯基越多的自由基电离势越低是雅阁的。最后给出了修正的Arrhenius表达式的优选速率参数。«少
The temperature-dependent rate parameters for the reactions of C/sub 2/H/sub 3/ and C/sub 4/H/sub 5/ with H/sub 2/ and C/sub 2/H/sub 2/ were calculated. Transition-state theory estimation methods developed by Benson were used to estimate frequency factors at 300 K, A(300), and heat capacities of activation ..delta..C/dagger//sub v/'s, over the temperature range of 300-1500 K. Recently published experimental measurements of the rate constants at 300 K, k(300), were used together with the estimated A(300) to derive the activation energies at 300 K, E(300). The ..delta..C/dagger//sub v/'s were used next to compute E(T), A(T), and k(T). The k(T) values were well reproduced by modified Arrhenius expressions, log k' = log A' + n log T-E'/2.3 RT, with n = /sub 300//sup 1500//R. The reactions with H/sub 2/ have small Arrhenius plot curvatures. The expression derived for a reverse reaction, H + C/sub 2/H/sub 4/ ..-->.. H/sub 2/ + C/sub 2/H/sub 3/, fits the high-temperature data published previously. The reactions of addition to C/sub 2/H/sub 2/ exhibit significant Arrhenius plot curvatures as expected for these three-electron, three-center transition states. The activation energies are lower than those of similar reactions of alkyl radicals, in accord with the lower ionization potentials ofmore » vinylic radicals. The preferred rate parameters for the modified Arrhenius expressions are given.« less