Brickel Sebastian, Meuwly Markus
Department of Chemistry, University of Basel , Klingelbergstrasse 80, 4056 Basel, Switzerland.
J Phys Chem A. 2017 Jul 13;121(27):5079-5087. doi: 10.1021/acs.jpca.7b02950. Epub 2017 Jun 29.
The OH-stretch induced dynamics in fluorosulfonic acid (HSOF) is characterized from a statistically significant number of trajectories using multisurface adiabatic reactive molecular dynamics (MS-ARMD) simulations. The global reactive potential energy surface, which describes H-transfer and HF-elimination, is parametrized at the MP2/6-311G++(2p,2d) level of theory with an accuracy of better than 1 kcal/mol. Excitation along the OH-local mode leads to H-transfer dynamics but elimination of HF is only observed for excitations with ν ≥ 6 for 1 out of 5000 trajectories. This finding differs fundamentally from the situation for vibrationally induced photodissociation of HSO and HSOCl, for which, even with excitations of 4 quanta along the OH-stretch mode, elimination of HO and HCl, respectively, is readily observed on the subnanosecond time scale. RRKM rates for HX-elimination in HSOX (X = F, Cl) only differ by a factor of 5. The findings from the reactive molecular dynamics simulations together with the RRKM results thus indicate that the origin for a closed HF-production channel is dynamical. This is also consistent with experimental findings for hydrofluoroethanes in shock tubes, which found pronounced non-RRKM behavior.
利用多表面绝热反应分子动力学（MS-ARMD）模拟，从大量具有统计意义的轨迹中表征了氟磺酸（HSOF）中OH伸缩振动诱导的动力学。描述H转移和HF消除的全局反应势能面在MP2/6-311G++(2p,2d)理论水平上进行参数化，精度优于1 kcal/mol。沿OH局域模式的激发导致H转移动力学，但在5000条轨迹中只有1条轨迹观察到对于ν≥6的激发会消除HF。这一发现与HSO和HSOCl的振动诱导光解离情况有根本不同，对于后者，即使沿OH伸缩模式激发4个量子，分别在亚纳秒时间尺度上也很容易观察到消除HO和HCl。HSOX（X = F，Cl）中HX消除的RRKM速率仅相差5倍。反应分子动力学模拟结果与RRKM结果共同表明，封闭的HF生成通道的起源是动力学的。这也与激波管中氢氟乙烷的实验结果一致，该实验发现了明显的非RRKM行为。
