OH自由基引发的1,3,5-三甲基苯的大气氧化机理和动力学–理论研究,New Journal of Chemistry

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OH自由基引发的1,3,5-三甲基苯的大气氧化机理和动力学–理论研究
New Journal of Chemistry ( IF 2.7 ) Pub Date : 2017-08-09 00:00:00 , DOI: 10.1039/c7nj01285c
S. Ponnusamy _{1,

2,

3,

4} , L. Sandhiya _{1,

2,

3,

4} , K. Senthilkumar _{1,

2,

3,

4}

Affiliation

通过电子结构计算从理论上研究了1,3,5-三甲基苯（TMB）与OH自由基的反应。的反应TMB与OH自由基是发现通过H-原子抽象和OH加成反应在C1和C2的位置进行TMB。在250至350 K的温度范围内，使用典型的变分过渡态理论（CVT）计算了初始H-吸附和OH加成反应的速率常数。的TMB -OH加合物（I4）是11.8×10的速率常数更有利^-12厘米³分子在298 K下为^-1 s^-1，在正常大气OH浓度下TMB的寿命为4小时。这些反应中最初形成的自由基通过与分子氧反应进行大气转化，从而形成过氧自由基中间体。过氧自由基与其他大气氧化剂如HO_2的反应NO导致生成产物，例如三甲基苯酚，双环过氧化物，双环羰基和甲基乙二醛。计算的热力学参数表明，与中间体和产物的形成相对应的反应是高度放热的。从当前的理论研究中获得的结果与现有文献非常吻合，并阐明了与大气中TMB氧化形成次生有机气溶胶相对应的反应途径。

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The atmospheric oxidation mechanism and kinetics of 1,3,5-trimethylbenzene initiated by OH radicals – a theoretical study

The reaction of 1,3,5-trimethylbenzene (TMB) with OH radicals is studied theoretically by using electronic structure calculations. The reaction of TMB with OH radicals is found to proceed by H-atom abstraction and OH addition reactions at the C1 and C2 positions of TMB. The rate constant is calculated for the initial H-abstraction and OH-addition reactions using canonical variational transition state theory (CVT) over the temperature range of 250 to 350 K. The results from the calculated thermodynamic parameters and kinetic calculations show that the formation of the TMB–OH adduct (I4) is more favorable with the rate constant of 11.8 × 10⁻¹² cm³ molecule⁻¹ s⁻¹ at 298 K and the lifetime of TMB is 4 hours at a normal atmospheric OH concentration. The initially formed radicals from these reactions undergo atmospheric transformation by reacting with molecular oxygen leading to the formation of peroxy radical intermediates. The reaction of peroxy radicals with other atmospheric oxidants, such as HO₂ and NO leads to the formation of products, such as trimethyl phenol, bicyclic peroxides, bicyclic carbonyl and methylglyoxal. The calculated thermodynamical parameters show that the reactions corresponding to the formation of the intermediates and products are highly exothermic. The results obtained from the current theoretical study are in excellent agreement with the available literature and elucidate the reaction pathways corresponding to the formation of secondary organic aerosols from TMB oxidation in the atmosphere.

更新日期：2017-09-11

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