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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Ab Initio Studies of ClO_x Radical Reactions: V. Evidence for a New Path in the Cl + ClOOCI Reaction
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Ab Initio Studies of ClO_x Radical Reactions: V. Evidence for a New Path in the Cl + ClOOCI Reaction

机译：ClO_x自由基反应的从头算研究：V. Cl + ClOOCI反应新途径的证据

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摘要

The mechanism for the reaction Cl + ClOOCl has been investigated by ab initio molecular orbital and transition-state theory calculations. The result shows that the reaction can produce both Cl_2 + ClOO and Cl_2O + ClO. The former product pair can be formed by direct and indirect abstraction paths. The direct abstraction path, which dominates at low temperatures, takes place barrierlessly with the rate constant k_1 = 1.53 * 10~(-13)T~(1.1) exp(118/T) cm~3 molecule~(-1) s~(-1) in the temperature range of 200-1000 K. The rate constant of the indirect path, which occurs via the two isomers of the Cl-O(Cl)OCl complex lying 3 kcal/mol below the reactants, kk_1' = 7.14 * 10~(-12)T~(0.86) exp(-2370/T) cm~3 molecule~(-1) s~(-1), accounting for less than 0.1% of the Cl_2 yield at 298 K but increasing to about 46% at 1000 K. The new Cl_2O + ClO products can be produced by the fragmentation of the two complexes; the rate constant for their formation was found to be pressure-independent and can be expressed by k_2 = 2.19 * 10~(-14)T~(0.70) exp(-1110/T) cm~3 molecule~(-1) s~(-1) covering the temperature range of 200-1000 K. Above room temperature, Cl_2O formation becomes competitive; for example, its branching ratios, k_2/k_t, are predicted to be 0.19, 0.55, and 0.62 at 298, 500, and 1000 K, respectively. The predicted total rate constant agrees closely with available experimental results. The heat of formation of ClOOCl has been examined in detail using different reactions and computational methods. The results of these calculations converge to Δ_fH°_0(ClOOCl) = 30 ± 2 kcal/mol.
机译：通过从头算的分子轨道和过渡态理论计算研究了Cl + ClOOCl反应的机理。结果表明该反应可以同时产生Cl_2 + ClOO和Cl_2O + ClO。前一个产品对可以由直接和间接抽象路径形成。在低温下占主导地位的直接提取路径无障碍地发生，速率常数k_1 = 1.53 * 10〜（-13）T〜（1.1）exp（118 / T）cm〜3分子〜（-1）s〜 （-1）在200-1000 K的温度范围内。间接路径的速率常数是通过位于反应物以下3 kcal / mol的Cl-O（Cl）OCl络合物的两个异构体产生的，kk_1'= 7.14 * 10〜（-12）T〜（0.86）exp（-2370 / T）cm〜3分子〜（-1）s〜（-1），占298 K时Cl_2收率的不到0.1％，但在1000 K下增加到约46％。新的Cl_2O + ClO产物可以通过两个络合物的断裂来产生;发现它们的形成速率常数与压力无关，可以表示为k_2 = 2.19 * 10〜（-14）T〜（0.70）exp（-1110 / T）cm〜3分子〜（-1）s 〜（-1）覆盖200-1000 K的温度范围。在室温以上，Cl_2O的形成变得竞争激烈;例如，其分支比k_2 / k_t分别在298、500和1000 K时预测为0.19、0.55和0.62。预测的总速率常数与可用的实验结果非常吻合。已经使用不同的反应和计算方法详细检查了ClOOCl的形成热。这些计算的结果收敛到Δ_fH°_0（ClOOCl）= 30±2 kcal / mol。

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