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Kinetics of Reactions of CCN Radical with Alcohols
Zhi-qiang Zhu ,Min Ji ,Shao-hua Zhang ,Lin-sen Pei ,Yang Chen*
Author NameAffiliation
Zhi-qiang Zhu Hefei National Laboratory for Physical Sciences at Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China 
Min Ji Hefei National Laboratory for Physical Sciences at Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China 
Shao-hua Zhang Hefei National Laboratory for Physical Sciences at Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China 
Lin-sen Pei Hefei National Laboratory for Physical Sciences at Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China 
Yang Chen* Hefei National Laboratory for Physical Sciences at Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China 
Abstract:
The reaction kinetics of cyanomethylidyne radical, CCN( eX2Π), with a series of primary alcohols were studied at about 1.33 kPa total pressure and room temperature using pulsed laser photolysis/laser-induced fluorescence (LP/LIF) technique. The CCN radical was produced via laser photolysis of CCl3CN with the fourth harmonic output of a Nd: YAG laser (266 nm). The relative concentration of the CCN( eX2Π) radical was monitored by LIF in the (0, 0) band of the CCN( ~ A2¢? eX2Π) transition at 470.9 nm. Under pseudofirst-order conditions, the reaction rate constants of CCN( eX2Π) with a series of primary alcohol molecules (n-CnH2n+1OH, n=1-6) were determined by measuring the time evolution of the relative concentration of CCN( eX2Πi). The measured rate constants increased monotonously with the number of carbon atoms in the alcohols, and the values for reactions of CCN( eX2Π) with alcohols were larger than those for reactions of CCN( eX2Π) with alkanes (C1-C5). Based on the bond dissociation energies and linear free energy correlations, it was believed that the reactions of CCN( eX2Π) with alcohols proceeded via a hydrogen abstraction mechanism that was analogous to CCN( eX2Π) with alkanes. The experimental results indicated that the H atoms on the C-H bonds were activated at the presence of the OH group in alcohol molecules and the hydrogen abstraction from the C-H bonds in the alcohol molecules was the dominant reaction pathway. The relation between the rate constants and the long-distance attractive potentials between the CCN radical and the alcohol molecules was discussed.
Key words:  Kinetics, Cyanomethylidyne radical, Alcohols
FundProject:
CCN与醇类分子的反应动力学
朱志强,计敏,张少华,裴林森,陈旸*
摘要:
用266 nm的激光光解CCl3CN分子产生CCN自由基,并在室温(298 K)和腔体总压为1.33 kPa的条件下,利用激光诱导荧光技术研究了CCN( eX2|)自由基与一系列醇类分子CnH2n+1OH(n=1?6)的反应动力学,通过实时监测反应体系中CCN( eX2|)浓度随反应时间的变化,测量了这些反应的总包速率常数.这些数据均是首次报道.结果显示,CCN( eX2|)自由基与醇类分子的反应速率常数随着醇分子中C原子数的增加而增大,而且均大于CCN( eX2|)与相应C原子数的烷烃分子的反应速率常数.基于键解离能相关和线性自由能相关地讨论,CCN( eX2|)自由基与醇类分子的反应应是一个抽氢反应;受醇分子中OH基团的诱导效应的影响,醇分子C-H键上的H具有较大的活性,因而CCN( eX2|)自由基抽提C-H键上的H是主要的反应通道. 同时还利用碰撞络合物模型和成轨理论来讨论了长程吸引势对反应的指前因子的影响
关键词:  反应动力学,CCN自由基,醇类
DOI:10.1360/cjcp2007.20(1).5.7
分类号: