Seta Takamasa, Nakajima Masakazu, Miyoshi Akira
Department of Chemical System Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
J Phys Chem A. 2006 Apr 20;110(15):5081-90. doi: 10.1021/jp0575456.
The rate constants for the reactions of OH radicals with benzene and toluene have been measured directly by a shock tube/pulsed laser-induced fluorescence imaging method at high temperatures. The OH radicals were generated by the thermal decomposition of nitric acid or tert-butyl hydroperoxide. The derived Arrhenius expressions for the rate constants were k(OH + benzene) = 8.0 x 10(-11) exp(-26.6 kJ mol(-1)/RT) [908-1736 K] and k(OH + toluene) = 8.9 x 10(-11) exp(-19.7 kJ mol(-1)/RT) [919-1481 K] in the units of cubic centimeters per molecule per second. Transition-state theory (TST) calculations based on quantum chemically predicted energetics confirmed the dominance of the H-atom abstraction channel for OH + benzene and the methyl-H abstraction channel for OH + toluene in the experimental temperature range. The TST calculation indicated that the anharmonicity of the C-H-O bending vibrations of the transition states is essential to reproduce the observed rate constants. Possible implications to the other analogous H-transfer reactions were discussed.
通过激波管/脉冲激光诱导荧光成像方法，在高温下直接测量了羟基自由基与苯和甲苯反应的速率常数。羟基自由基由硝酸或叔丁基过氧化氢的热分解产生。速率常数的阿伦尼乌斯表达式为k(OH + 苯) = 8.0 x 10(-11) exp(-26.6 kJ mol(-1)/RT) [908 - 1736 K] 和k(OH + 甲苯) = 8.9 x 10(-11) exp(-19.7 kJ mol(-1)/RT) [919 - 1481 K]，单位为立方厘米每分子每秒。基于量子化学预测能量学的过渡态理论（TST）计算证实，在实验温度范围内，OH + 苯反应中氢原子夺取通道占主导，OH + 甲苯反应中甲基氢夺取通道占主导。TST计算表明，过渡态C - H - O弯曲振动的非谐性对于重现观测到的速率常数至关重要。讨论了对其他类似氢转移反应的可能影响。
