Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA.
J Phys Chem A. 2010 Nov 18;114(45):12088-98. doi: 10.1021/jp1062786. Epub 2010 Oct 26.
The rate coefficients of H-abstraction reactions of butene isomers by the OH radical were determined by both canonical variational transition-state theory and transition-state theory, with potential energy surfaces calculated at the CCSD(T)/6-311++G(d,p)//BH&HLYP/6-311G(d,p) level and CCSD(T)/6-311++G(d,p)//BH&HLYP/cc-pVTZ level and quantum mechanical tunneling effect corrected by either the small-curvature tunneling method or the Eckart method. While 1-butene contains allylic, vinylic, and alkyl hydrogens that can be abstracted to form different butene radicals, results reveal that s-allylic H-abstraction channels have low and broad energy barriers, and they are the most dominant channels which can occur via direct and indirect H-abstraction channels. For the indirect H-abstraction s-allylic channel, the reaction can proceed via forming two van der Waals prereactive complexes with energies that are 2.7-2.8 kcal mol(-1) lower than that of the entrance channel at 0 K. Assuming that neither mixing nor crossover occurs between different reaction pathways, the overall rate coefficient was calculated by summing the rate coefficients of the s-allyic, methyl, and vinyl H-abstraction paths and found to agree well with the experimentally measured OH disappearance rate. Furthermore, the rate coefficients of p-allylic H abstraction of cis-2-butene, trans-2-butene, and isobutene by the OH radical were also determined at 300-1500 K, with results analyzed and compared with available experimental data.
通过正则变分过渡态理论和过渡态理论，结合 CCSD(T)/6-311++G(d,p)//BH&HLYP/6-311G(d,p) 和 CCSD(T)/6-311++G(d,p)//BH&HLYP/cc-pVTZ 水平下计算的势能面，以及通过小曲率隧道效应或 Eckart 方法修正的量子力学隧道效应，确定了丁烯异构体与 OH 自由基的 H 提取反应的速率系数。虽然 1-丁烯包含烯丙基、乙烯基和烷基氢，可以被提取形成不同的丁烯自由基，但结果表明 s-烯丙基 H 提取通道具有较低和较宽的能垒，它们是最主要的通道，可以通过直接和间接 H 提取通道发生。对于间接 H 提取的 s-烯丙基通道，反应可以通过形成两个范德华预反应复合物进行，其能量比 0 K 时入口通道低 2.7-2.8 kcal/mol。假设不同反应途径之间既不混合也不交叉，通过将 s-烯丙基、甲基和乙烯基 H 提取路径的速率系数相加，计算得到的总速率系数与实验测量的 OH 消失速率吻合良好。此外，还在 300-1500 K 下测定了 OH 自由基对顺式-2-丁烯、反式-2-丁烯和异丁烯的 p-烯丙基 H 提取的速率系数，并对实验数据进行了分析和比较。
