Thomas Javix, Serrato Agapito, Lin Wei, Jäger Wolfgang, Xu Yunjie
Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 (Canada), Fax: (+1) 780-492-8231.
Chemistry. 2014 May 12;20(20):6148-53. doi: 10.1002/chem.201304321. Epub 2014 Apr 22.
Rotational spectra of perfluorobutyric acid (PFBA) and its monohydrate were studied with a broadband chirped pulse and a narrow-band cavity based Fourier transform microwave spectrometer, and high-level ab initio calculations. Extensive conformational searches were performed for both the acid and its monohydrate at the MP2/6-311++G(2d,p) level of theory. Two and three conformers were predicted to exist for PFBA and its monohydrate, respectively. One set of rotational transitions was observed and assigned for each, PFBA and its monohydrate. Based on the measured broadband spectra, we confidently conclude that only one dominant conformer exists in each case. The orientation of the hydroxyl group in PFBA was determined by using isotopic analysis. Comparison of the observed transition intensities and the calculated electric dipole moment components allowed us to identify the most stable monohydrate conformation, which takes on an insertion hydrogen-bonding topology. Comparisons to the shorter chain analogues, that is, trifluoroacetic acid, perfluoropropionic acid, and their monohydrates, are made to elucidate the general trend in their conformational preference and binding topologies.
使用宽带啁啾脉冲和基于窄带腔的傅里叶变换微波光谱仪以及高水平的从头算计算方法，研究了全氟丁酸（PFBA）及其一水合物的转动光谱。在MP2/6-311++G(2d,p)理论水平上对该酸及其一水合物进行了广泛的构象搜索。预测PFBA及其一水合物分别存在两种和三种构象异构体。分别观测并归属了PFBA及其一水合物的一组转动跃迁。基于测得的宽带光谱，我们有把握地得出结论，在每种情况下仅存在一种主要构象异构体。通过同位素分析确定了PFBA中羟基的取向。比较观测到的跃迁强度和计算得到的电偶极矩分量，使我们能够确定最稳定的一水合物构象，其呈现插入式氢键拓扑结构。与较短链类似物（即三氟乙酸、全氟丙酸及其一水合物）进行比较，以阐明它们在构象偏好和结合拓扑结构方面的一般趋势。
