Departamento de Físico-Química, Instituto de Química, Universidade Federal da Bahia Rua Barão de Jeremoabo, 147, Salvador, Bahia 40170-115, Brazil.
J Phys Chem A. 2022 Jul 28;126(29):4791-4800. doi: 10.1021/acs.jpca.2c03305. Epub 2022 Jul 15.
Thermal rate coefficients for the hydrogen abstraction reactions of prenol (3-methyl-2-butenol) by a hydrogen atom were calculated with the multipath canonical variational theory with small-curvature tunneling (MP-CVT/SCT). The conformational search was performed with a dual-level approach, and the multistructural torsional anharmonicity effects were corrected through the rovibrational partition function calculated with the multistructural method based on a coupled torsional potential (MS-T(C)). This methodology allows us to estimate the thermal rate constants in the temperature range of 200-2500 K and fit them into two analytical expressions. Differences between the number of conformations on the torsional potential energy surfaces for prenol and the transition state decrease the thermal rate constants for the H-abstraction at the α carbon. An opposite behavior was detected for the abstractions on the δ site. The product branching ratios were calculated using single-structure and multipath approaches. The product distributions from the former are shown to be inadequate for studying the mechanism under combustion conditions. The values estimated from MP-CVT/SCT rate coefficients indicated that the radicals from () and ()/() are formed in considerable amounts. These species are fundamental in comprehending the inhibition and promotion of the autoignition phenomena.
用多路径正则变分理论结合小曲率隧道效应（MP-CVT/SCT）计算了异戊烯醇（3-甲基-2-丁烯醇）与氢原子的氢提取反应的速率系数。构象搜索采用双水平方法进行，多结构扭转非谐效应通过基于耦合扭转势的多结构方法（MS-T(C)）计算的振转配分函数进行修正。这种方法使我们能够在 200-2500 K 的温度范围内估算热速率常数，并将其拟合为两个分析表达式。异戊烯醇在扭转势能表面上的构象数与过渡态之间的差异降低了α碳上 H 提取的热速率常数。在 δ 位点的提取中检测到相反的行为。使用单结构和多路径方法计算产物分支比。从前者得出的产物分布表明，在燃烧条件下研究该机制是不充分的。从 MP-CVT/SCT 速率系数估计的值表明，（）和（）/（）自由基以相当大的量形成。这些物质对于理解自动点火现象的抑制和促进是基本的。
