Molecular Structures and Microwave Spectra of the Gas-Phase Homodimers of 3-Fluoro-1,2-epoxypropane and 3,3-Difluoro-1,2-epoxypropane
Molecular Structures and Microwave Spectra of the Gas-Phase Homodimers of 3-Fluoro-1,2-epoxypropane and 3,3-Difluoro-1,2-epoxypropane
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3-氟-1,2-环氧丙烷和3,3-二氟-1,2-环氧丙烷气相同二聚体的分子结构和微波谱
DOI：
10.1021/acs.jpca.3c03643
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Leung, Helen O.
中科院分区：
文献类型：
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作者：
Marshall, Mark D.;Leung, Helen O.
用从头算和密度泛函量子化学方法研究了3-氟-1，2-环氧丙烷和3，3-二氟-1，2-环氧丙烷的杂手性和同手性气相均二聚体的分子结构。虽然杂手性二聚体的微波光谱没有观察到，因为最低能量的异构体没有电偶极矩，而其他异构体的能量可能太高，但每个分子的同手性二聚体的旋转光谱与每个分子的最低能量异构体一致。氟甲基中氢原子的存在使这些基团有可能参与稳定这些二聚体的分子间相互作用，导致了与3，3，3-三氟-1，2-环氧丙烷均二聚体中观察到的截然不同的成键基序，而3，3，3-三氟-1，2-环氧丙烷中缺少氢原子阻止了这种可能性。用适度的计算方法可以很好地预测二聚体的转动光谱和能量有序性，从而能够直接指定观察到的光谱并识别指定光谱的分子载体。
Molecular structures for the heterochiral and homochiral gas-phase homodimers of 3-fluoro-1,2-epoxypropane and 3,3-difluoro-1,2-epoxypropane are investigated using both ab initio and density functional quantum chemistry calculations. Although microwave spectra for the heterochiral dimers are not observed as the lowest-energy isomers lack an electric dipole moment and others are presumably too high in energy, rotational spectra are observed for the homochiral dimers of each molecule that are consistent with the lowest-energy isomers of each. The presence of hydrogen atoms in the fluoromethyl groups makes it possible for these groups to participate in the intermolecular interactions that stabilize these dimers, resulting in a distinctly different bonding motif than is observed in the homodimers of 3,3,3-trifluoro-1,2-epoxypropane where the lack of a hydrogen atom prevents this possibility. The rotational spectra and energy ordering of the dimers are sufficiently well predicted with modest calculational methods to enable straightforward assignment of the observed spectra and to identify the molecular carrier of an assigned spectrum.