Kinetics of gas-phase reaction of OH with morpholine: an experimental and theoretical study.
Kinetics of gas-phase reaction of OH with morpholine: an experimental and theoretical study.
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OH 与吗啉的气相反应动力学：实验和理论研究。
DOI：
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发表时间：
2010
影响因子：
2.9
通讯作者：
P. Bajaj
中科院分区：
文献类型：
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作者：
S. Sengupta;Yogesh N. Indulkar;Adarsh Kumar;S. Dhanya;P. Naik;P. Bajaj
采用激光光解-激光诱导荧光技术，在298 ~ 363 K温度范围内研究了OH自由基与含氧、氮杂环分子啉的反应动力学。室温下的速率常数（k(298)）为（8.0 +/- 0.1）× 10（-11）分子（-1）cm(3) s（-1）。在研究范围内，速率常数随温度的升高而减小，其近似依赖关系为k(T) = (1.1 +/- 0.1) x 10(-11) exp[(590 +/- 20)/T] cm(3)分子（-1）s（-1）。与类似的含氧原子杂环分子相比，其速率常数较高，但与脂肪族胺的速率常数相当。从头算分子轨道计算表明，与反应物相比，反应前配合物的能量低5-7千卡摩尔（-1），是由OH与啉的N/O原子之间的氢键相互作用形成的。发现含有氮原子的络合物比含有氧原子的络合物更稳定。从这些预反应络合物中提取氢的不同途径的优化过渡态结构和能量解释了观察到的负活化能。
Kinetics of reaction of OH radical with morpholine, a heterocyclic molecule with both oxygen and nitrogen atoms, has been investigated using laser photolysis-laser-induced fluorescence technique, in the temperature range of 298-363 K. The rate constant at room temperature (k(298)) is (8.0 +/- 0.1) x 10(-11) molecule(-1) cm(3) s(-1). The rate constant decreases with temperature in the range studied, with the approximate dependence given by k(T) = (1.1 +/- 0.1) x 10(-11) exp[(590 +/- 20)/T] cm(3) molecule(-1) s(-1). The rate constants are high compared with those of similar heterocyclic molecules with oxygen atom but comparable to those reported for aliphatic amines. Ab initio molecular orbital calculations show that prereactive complexes, 5-7 kcal mol(-1) lower in energy as compared with the reactants, are formed because of hydrogen bond interaction between OH and the N/O atom of morpholine. The stability of the complex involving the nitrogen atom is found to be more than that involving the oxygen atom. The optimized transition-state structures and energies for the different pathways of hydrogen abstraction from these prereactive complexes explain the observation of negative activation energy.