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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Kinetic and Mechanism of the Gas-Phase Reaction of Cl Atoms with Benzene
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Kinetic and Mechanism of the Gas-Phase Reaction of Cl Atoms with Benzene

机译：Cl原子与苯气相反应的动力学及机理

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The gas-phase reaction of Cl atoms with benzene has been studied using both experimental and computational methods. The bulk of the kinetic data were obtained using steady-state photolysis of mixtures containing Cl_2, C_6H_6, and a reference compound in 120-700 Torr of N_2 diluent at 296 K. Reaction of Cl atoms with C_6H_6 proceeds via two pathways; (a) H-atom abstraction and (b) adduct formation. At 296 K the rate constant for the abstraction channel is k_(1a) = (1.3 ± 1.0) * 10~(-16) cm~3 molecules~(-1) s~(-1). Phenyl radicals produced via H-atom abstraction from C_6H_6 react with Cl_2 to give chlorobenzene. The main fate of the C_6H_6-Cl adduct is decomposition to reform C_6H_6 and Cl atoms. A small fraction of the C_6H_6-Cl adduct undergoes reaction with Cl atoms via a mechanism which does not lead to the production of C_6H_5Cl_, or the reformation of C_6H_6. As the steady-state Cl atom concentration is increased, the fraction of the C_6H_6-Cl adduct undergoing reaction with Cl atoms increases causing an increase in the effective rate constant for benzene removal and a decrease in the chlorobenzene yield. Thermodynamic calculations show that a rapid equilibrium is established between Cl atoms, C_6H_6, and the C_6H_6-Cl adduct, and it is estimated that at 296 K the equilibrium constant is K_(c, 1b) = [C_6H_6-Cl]/[C_6H_6][Cl] and lies in the range (1-2) * 10~(-18) cm~3 molecule. ~1 Flash photolysis experiments conducted using C_6H_6/Cl_2 mixtures in 760 Torr of either N_2 or O_2 diluent at 296 K did not reveal any significant transient UV absorption; this is entirely consistent with results from the steady-state experiments and the thermodynamic calculations. The C_6H_6-Cl adduct reacts slowly (if at all) with O_2 and an upper limit of k(C_6H_6-Cl + O_2) < 8 * 10~(-17) cm~3 molecule~(-1) s~(-1) was established. As part of this work a value of k(Cl + CF_2ClH) = (1.7 ± 0.1) * 10~(15) cm~3 molecule~(-1) s~(-1) was measured. These results are discussed with respect to the available literature concerning the reaction of Cl atoms with benzene.
机译：已经使用实验和计算方法研究了Cl原子与苯的气相反应。大量的动力学数据是通过在296 K下在120-700 Torr的N_2稀释剂中对含Cl_2，C_6H_6和参考化合物的混合物进行稳态光解获得的。Cl原子与C_6H_6的反应通过两个途径进行： （a）H原子的提取和（b）加合物的形成。在296 K时，抽象通道的速率常数为k_（1a）=（1.3±1.0）* 10〜（-16）cm〜3分子〜（-1）s〜（-1）。通过C_6H_6的H原子抽象产生的苯基与Cl_2反应生成氯苯。 C_6H_6-Cl加合物的主要命运是分解以重整C_6H_6和Cl原子。 C_6H_6-Cl加合物中的一小部分通过不会导致C_6H_5Cl_生成或C_6H_6重整的机理与Cl原子反应。随着稳态Cl原子浓度的增加，与Cl原子反应的C_6H_6-Cl加合物的分数增加，导致除苯有效速率常数增加，氯苯产率降低。热力学计算表明，Cl原子，C_6H_6和C_6H_6-Cl加合物之间建立了快速平衡，并且估计在296 K时平衡常数为K_（c，1b）= [C_6H_6-Cl] / [C_6H_6] [Cl]的范围为（1-2）* 10〜（-18）cm〜3分子。使用C_6H_6 / Cl_2混合物在760 Torr的N_2或O_2稀释剂中在296 K下进行的〜1快速光解实验没有发现任何明显的瞬时UV吸收。这与稳态实验和热力学计算的结果完全一致。 C_6H_6-Cl加合物与O_2反应缓慢（如果有的话），并且上限k（C_6H_6-Cl + O_2）<8 * 10〜（-17）cm〜3分子〜（-1）s〜（-1 ） 建立了。作为这项工作的一部分，测量了k（Cl + CF_2ClH）=（1.7±0.1）* 10〜（15）cm〜3分子〜（-1）s〜（-1）的值。关于关于Cl原子与苯反应的现有文献讨论了这些结果。

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