Rotational spectra of the 4-fluoroacetophenone monomer and its monohydrate were investigated by Fourier transform microwave spectroscopy complemented with quantum chemical calculations. One conformer of 4-fluoroacetophenone and two isomers of 4-fluoroacetophenone–H₂O have been observed in the pulsed jets. The observation of all mono-substituted ¹³C isotopologues in natural abundance allows an accurate structural determination of the 4-fluoroacetophenone monomer. Both detected isomers of 4-fluoroacetophenone–H₂O are stabilized by a dominant O–H⋯O and a secondary C–H⋯O hydrogen bond. The fluorination effects on the geometries, intermolecular non-covalent interactions and V₃ barrier of the methyl internal rotation were analysed. The relative population ratio of the two observed isomers for 4-fluoroacetophenone–H₂O was also estimated to be N_I/N_II ≈ 7/1.

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4-氟苯乙酮及其一水合物的氟化效应探讨

通过傅里叶变换微波光谱并辅以量子化学计算研究了 4-氟苯乙酮单体及其一水合物的旋转光谱。在脉冲射流中观察到了4-氟苯乙酮的一种构象异构体和 4-氟苯乙酮-H _{2 O 的两种异构体。}观察天然丰度的所有单取代¹³ C 同位素异数体可以准确确定 4-氟苯乙酮单体的结构。检测到的 4-氟苯乙酮-H ₂ O 的两种异构体均通过占主导地位的 O-H⋯O 和次要的 C-H⋯O 氢键稳定。分析了氟化对甲基内旋转的几何形状、分子间非共价相互作用和V _{3势垒的影响。}4-氟苯乙酮-H ₂ O 的两种观察到的异构体的相对总体比率也估计为N _I / N _II ≈ 7/1。