Cheramangalath Balan Ramya, Rajakumar B
Department of Chemistry , Indian Institute of Technology Madras , Chennai 600036 , India.
J Phys Chem A. 2019 May 23;123(20):4342-4353. doi: 10.1021/acs.jpca.9b00995. Epub 2019 May 10.
The temperature-dependent rate coefficients for the gas-phase reaction of 4-hydroxy-2-butanone (4H2BN) with Cl atoms and OH radicals were explored experimentally using relative rate technique and computational methods. The concentrations of the reactants as well as products were followed using gas chromatography (GC) with the flame ionization detector, GC/mass spectrometry, and GC/infrared spectroscopy as analytical techniques. Formaldehyde was obtained as the major product during the title reaction. The kinetics of 4H2BN with Cl atoms and OH radicals were measured over the temperature range of 298-363 K at 760 Torr in the N atmosphere using CH, CH, isopropanol, and n-propanol as reference compounds. The temperature-dependent rate coefficients for the reaction of 4H2BN with Cl atoms and OH radicals were obtained as k( T) = [(1.52 ± 0.86) × 10] T exp[(2474 ± 450)/ T] cm molecule s and k( T) = [(2.09 ± 0.24) × 10] exp[-(409 ± 15)/ T] cm molecule s, respectively. Theoretical calculations were carried out at the M062X/6-31G(d,p) and M06-2X/6-31+G(d,p) level of theories, and the rate coefficients for H abstraction reactions were evaluated using the canonical variational transition state theory with the inclusion of small-curvature tunneling correction over the temperature range of 200-400 K. The rate coefficients obtained over the studied temperature range were used to fit the data, and the Arrhenius expression was obtained to be k (200-400 K) = (6.10 × 10) T exp(2397/ T) cm molecule s, k (200-400 K) = (1.13 × 10) T exp(1505/ T) cm molecule s, respectively, for the reactions of Cl atoms and OH radicals with 4H2BN. The possible reaction mechanism proposed based on the obtained products for the title reaction, thermochemistry, branching ratios, and atmospheric implications and cumulative lifetime of 4H2BN were also explored in this study.
采用相对速率技术和计算方法，对4-羟基-2-丁酮（4H2BN）与氯原子和羟基自由基的气相反应的温度依赖速率系数进行了实验研究。使用配备火焰离子化检测器的气相色谱（GC）、GC/质谱以及GC/红外光谱作为分析技术，跟踪反应物和产物的浓度。在标题反应中，甲醛是主要产物。在N2气氛、760 Torr压力下，于298 - 363 K的温度范围内，以CH4、C2H6、异丙醇和正丙醇作为参考化合物，测定了4H2BN与氯原子和羟基自由基的动力学。4H2BN与氯原子和羟基自由基反应的温度依赖速率系数分别为k(T) = [(1.52 ± 0.86) × 10^-10]T exp[(2474 ± 450)/T] cm^3 molecule^-1 s^-1和k(T) = [(2.09 ± 0.24) × 10^-12] exp[-(409 ± 15)/T] cm^3 molecule^-1 s^-1。在M062X/6 - 31G(d,p)和M06 - 2X/6 - 31+G(d,p)理论水平上进行了理论计算，并在200 - 400 K的温度范围内，使用包含小曲率隧道效应校正的正则变分过渡态理论评估了氢原子提取反应的速率系数。在所研究的温度范围内获得的速率系数用于拟合数据，对于氯原子和羟基自由基与4H2BN的反应，得到的阿伦尼乌斯表达式分别为k(200 - 400 K) = (6.10 × 10^-11)T exp(2397/T) cm^~3 molecule^-1 s^-1和k(200 - 400 K) = (1,13 × 10^-12)T exp(1505/T) cm^3 molecule^-1 s^-1。本研究还基于所获得的标题反应产物、热化学、分支比、大气影响以及4H2BN的累积寿命，探讨了可能的反应机理。
