Kaur Ramanpreet
Quantum Chemistry Group, Department of Chemistry and Centre of Advanced Studies in Chemistry, Panjab University, Chandigarh 160014, India.
J Chem Phys. 2015 Feb 21;142(7):074307. doi: 10.1063/1.4907593.
2-Aminopropionitrile (APN), a probable candidate as a chiral astrophysical molecule, is a precursor to amino-acid alanine. Stereochemical pathways in 2-APN are explored using Global Reaction Route Mapping (GRRM) method employing high-level quantum-mechanical computations. Besides predicting the conventional mechanism for chiral inversion that proceeds through an achiral intermediate, a counterintuitive flipping mechanism is revealed for 2-APN through chiral intermediates explored using the GRRM. The feasibility of the proposed stereochemical pathways, in terms of the Gibbs free-energy change, is analyzed at the temperature conditions akin to the interstellar medium. Notably, the stereoinversion in 2-APN is observed to be more feasible than the dissociation of 2-APN and intermediates involved along the stereochemical pathways, and the flipping barrier is observed to be as low as 3.68 kJ/mol along one of the pathways. The pathways proposed for the inversion of chirality in 2-APN may provide significant insight into the extraterrestrial origin of life.
2-氨基丙腈（APN）可能是一种手性天体物理分子，是氨基酸丙氨酸的前体。采用高级量子力学计算的全局反应路线图（GRRM）方法探索了2-APN中的立体化学途径。除了预测通过非手性中间体进行的手性反转的传统机制外，通过使用GRRM探索的手性中间体，还揭示了2-APN的一种违反直觉的翻转机制。在所提出的立体化学途径的可行性方面，在类似于星际介质的温度条件下分析了吉布斯自由能变化。值得注意的是，观察到2-APN中的立体反转比2-APN的解离以及沿立体化学途径涉及的中间体更可行，并且沿其中一条途径观察到的翻转势垒低至3.68 kJ/mol。为2-APN中的手性反转提出的途径可能为地球外生命起源提供重要见解。
