Yap Kaili, Krantzman Kristin D, Lavrich Richard J
Department of Chemistry and Biochemistry, College of Charleston, 66 George Street, Charleston, South Carolina 29424, United States.
J Phys Chem A. 2023 Sep 28;127(38):7892-7897. doi: 10.1021/acs.jpca.3c03485. Epub 2023 Sep 15.
This combined experimental and theoretical study seeks to determine the role that inductive effects have on hydrogen bonds by an investigation into the change in intramolecular hydrogen bond strength in 2-amino-1-trifluoromethylethanol (2ATFME) relative to that in 2-aminoethanol (2AE). Toward this end, the rotational spectra of the normal, C, and N isotopologues have been measured using Fourier transform microwave spectroscopy and fit to the rotational, quadrupole coupling, and centrifugal distortion constants of the Watson A-reduction Hamiltonian. Structural parameters used to characterize the strength of the intramolecular hydrogen bond have been determined from the experimental structures of both 2ATFME and 2AE as well as from MP2/6-311++G(d,p) calculations. A comparison of these parameters in 2ATFME with those of 2AE indicates that the electron-withdrawing trifluoromethyl CF group strengthens the hydrogen bond. These include a 4% decrease in the distance between the donor and acceptor heavy atoms of the hydrogen bond, a 6% increase toward linearity of the OH···N angle, and a 23% decrease of the COH···N torsional angle toward planarity in 2ATFME relative to 2AE. This trend toward increased intramolecular hydrogen bond strength in 2ATFME is also observed within the ab initio structures.
这项结合了实验和理论的研究旨在通过研究2-氨基-1-三氟甲基乙醇（2ATFME）相对于2-氨基乙醇（2AE）分子内氢键强度的变化，来确定诱导效应在氢键中所起的作用。为此，使用傅里叶变换微波光谱法测量了正常、碳和氮同位素异构体的转动光谱，并将其拟合到沃森A约化哈密顿量的转动、四极耦合和离心畸变常数上。用于表征分子内氢键强度的结构参数已根据2ATFME和2AE的实验结构以及MP2/6-311++G(d,p)计算确定。将2ATFME中的这些参数与2AE的参数进行比较表明，吸电子的三氟甲基CF基团增强了氢键。相对于2AE，这些变化包括氢键供体和受体重原子之间的距离减少4%，OH···N角的线性度增加6%，以及2ATFME中COH···N扭转角向平面性减少23%。在从头算结构中也观察到2ATFME中分子内氢键强度增加的这种趋势。
