Computational study on the recombination reaction between benzyl and propargyl radicals
Computational study on the recombination reaction between benzyl and propargyl radicals
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DOI：
10.1002/kin.20625
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发表时间：
2012-03-01
影响因子：
1.5
通讯作者：
Miyoshi, Akira
中科院分区：
文献类型：
--
作者：
Matsugi, Akira;Miyoshi, Akira
采用B3LYP、CBS-QB3和CASPT2量子化学方法和基于RiceRamspergerKasselMarcus理论的稳态单分子主方程分析，对苯基与丙炔自由基复合反应的动力学和机理进行了计算研究。在CASPT2/cc-pVTZ//B3LYP/6-311G（d,p）水平上研究了由自由基的非等效共振结构引起的6种不同的重组通道（3种为苄基，2种为丙炔基），并利用变分跃迁态理论计算了各自的速率常数。结果表明，该反应主要由丙炔自由基加成到苄基自由基的- (CH2)位点上进行，邻位和对位的加成由于芳香性的丧失而不利。确定了初始形成的加合物通过双自由基中间体与亚甲基环戊烷融合化合物的异构化反应途径。二自由基和甲基化茚的直接h原子消除反应也可产生亚甲基茚自由基。主方程分析结果表明，1-亚甲基-2-吲哚基自由基主要在高温（0 ~ 1500 K）下生成，但总速率常数明显小于研究压力范围内的高压极限（0.001100 atm）。三联体双基通过系间交叉的反应也被认为是重要的，并进行了定性讨论。对1-亚甲基-2-吲哚基自由基后续反应的研究表明，这些自由基可迅速分解为1-亚甲基或萘+ h。(C) 2012 Wiley期刊公司中国生物医学工程学报，23 (4):444 - 444,2012
The kinetics and mechanisms of the recombination reaction between benzyl and propargyl radicals have been computationally investigated by using the B3LYP, CBS-QB3, and CASPT2 quantum chemical methods, and the steady-state unimolecular master equation analysis based on the RiceRamspergerKasselMarcus theory. Six distinct recombination channels arising from the radicals' nonequivalent resonance structures (three for benzyl and two for propargyl) were investigated at the CASPT2/cc-pVTZ//B3LYP/6-311G(d,p) level, and the respective rate constants were calculated with the variational transition state theory. It was found that the reaction dominantly proceeds by the addition of the propargyl radical to the alpha(CH2) site of the benzyl radical and the additions to the ortho- and the para-sites are unfavorable due to the loss of the aromaticity. The isomerization reaction pathways of the initially formed adducts to methylenecyclopenta-fused compounds through diradical intermediates were identified. Methyleneindanyl radicals were also identified as products, which are produced by direct H-atom elimination reactions from the diradical and methylenated indanes. The results of the master equation analyses indicated that the 1-methylene-2-indanyl radical is dominantly produced at high temperature (>1500 K), but the overall rate constant is significantly smaller than the high-pressure limit within the pressure range studied (0.001100 atm). The reactions of the triplet biradicals via the intersystem crossing were also suggested to be important and are discussed qualitatively. Investigations on the subsequent reactions of 1-methylene-2-indanyl radicals revealed that the radicals rapidly decompose to 1-methyleneindene or naphthalene + H. The temperature- and pressure-dependent rate expressions are proposed for kinetic modeling. (C) 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 206218, 2012