Kaur Ramanpreet, Rani Namrata
Quantum Chemistry Group, Department of Chemistry & Centre of Advanced Studies in Chemistry, Panjab University, Chandigarh 160014, India.
ACS Omega. 2018 Oct 31;3(10):14431-14447. doi: 10.1021/acsomega.8b01721.
Noncatalytic reaction pathways for the gas-phase stereoinversion in aspartic acid are mapped employing a global reaction route mapping strategy using quantum mechanical computations. The species including the transition states (TSs) traced along the stereoinversion pathways are characterized using rotational and vibrational computational spectroscopic analysis while accounting for the vibrational corrections to rotational constants and anharmonic effects. Notably, the TS structures traced along the stereochemical pathways resemble the achiral ammonium ylide and imine intermediates as observed in the Strecker synthesis of chiral amino acids. A few of the probable stereoinversion pathways proposed proceed through the proton or hydrogen atom transfer. The feasibility of the pathways under conditions akin to interstellar medium (ISM) is further discussed in terms of natural bond orbital analysis. The stereoinversion pathways proposed in this work may proceed via photoirradiation in the ISM, which though can be revealed by exploring the excited-state potential energy surface. In this context, the spectroscopic data generated in this work can provide valuable assistance toward the astrophysical detection of chiral molecules in outer space.
采用量子力学计算的全局反应路径映射策略，绘制了天冬氨酸气相立体反转的非催化反应路径。沿着立体反转路径追踪的包括过渡态（TSs）在内的物种，通过旋转和振动计算光谱分析进行表征，同时考虑了对旋转常数的振动校正和非谐效应。值得注意的是，沿着立体化学路径追踪的TS结构类似于在手性氨基酸的斯特雷克合成中观察到的非手性铵叶立德和亚胺中间体。提出的一些可能的立体反转路径是通过质子或氢原子转移进行的。根据自然键轨道分析，进一步讨论了在类似于星际介质（ISM）的条件下这些路径的可行性。这项工作中提出的立体反转路径可能通过ISM中的光照射进行，这虽然可以通过探索激发态势能面来揭示。在此背景下，这项工作中生成的光谱数据可为外层空间手性分子的天体物理探测提供有价值的帮助。
