Department of Chemical Sciences, Tezpur University, Napaam, Tezpur, Assam 784 028, India.
J Mol Model. 2013 Jun;19(6):2189-95. doi: 10.1007/s00894-013-1762-7. Epub 2013 Jan 25.
Theoretical investigations are carried out on reaction mechanism of the reactions of CF3CH2NH2 (TFEA) with the OH radical by means of ab initio and DFT methods. The electronic structure information on the potential energy surface for each reaction is obtained at MPWB1K/6-31+G(d,p) level and energetic information is further refined by calculating the energy of the species with a Gaussian-2 method, G2(MP2). The existence of transition states on the corresponding potential energy surface is ascertained by performing intrinsic reaction coordinate (IRC) calculation. Our calculation indicates that the H abstraction from -NH2 group is the dominant reaction channel because of lower energy barrier. The rate constants of the reaction calculated using canonical transition state theory (CTST) utilizing the ab initio data. The agreement between the theoretical and experimental rate constants is good at the measured temperature. From the comparison with CH3CH2NH2, it is shown that the fluorine substution decreases the reactivity of the C-H bond.
采用从头算和密度泛函理论方法对 CF3CH2NH2（TFEA）与 OH 自由基反应的反应机理进行了理论研究。在 MPWB1K/6-31+G(d,p)水平上获得了每个反应的势能表面上的电子结构信息，并通过使用 Gaussian-2 方法（G2(MP2)）计算物种的能量进一步细化了能量信息。通过进行内禀反应坐标（IRC）计算确定了相应势能表面上过渡态的存在。我们的计算表明，由于较低的能垒，-NH2 基团的 H 提取是主要的反应通道。使用从头算数据通过正则过渡态理论（CTST）计算得到的反应速率常数。在测量温度下，理论和实验速率常数之间具有良好的一致性。与 CH3CH2NH2 的比较表明，氟取代降低了 C-H 键的反应性。
