Bergmann Katrina, van Wijngaarden Jennifer
Department of Chemistry, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada.
J Phys Chem A. 2020 Mar 19;124(11):2270-2278. doi: 10.1021/acs.jpca.0c00744. Epub 2020 Mar 9.
The rotational spectra of 2-fluoroanisole and 3-fluoroanisole were investigated using Fourier transform microwave spectroscopy in the 4-26 GHz range. Assigned transitions correspond to the lowest energy rotamer for 2-fluoroanisole which has the O-CH group directed away () from the fluorine substituent whereas for 3-fluoroanisole, the spectrum is consistent with the presence of two rotamers arising from and orientations of the methoxy moiety relative to fluorine. calculations at the MP2/cc-pVTZ level were used to estimate the equilibrium () geometries of the three observed rotamers. Their assignments were confirmed through the observation of the rotational transitions of eight minor isotopologues (C and O) in natural abundance for each species. The mass dependence () structures derived using the experimentally determined rotational constants compare favorably with the estimates. The resulting sets of geometric parameters suggest that the aromatic ring backbone is distorted by the introduction of the angular methoxy substituent, with a tendency to induce bond length alternation around the ring, and by the electron withdrawing effects of fluorine.
在4 - 26 GHz范围内，使用傅里叶变换微波光谱法研究了2 - 氟苯甲醚和3 - 氟苯甲醚的转动光谱。已归属的跃迁对应于2 - 氟苯甲醚能量最低的旋转异构体，其中O - CH基团远离氟取代基，而对于3 - 氟苯甲醚，光谱与由甲氧基部分相对于氟的 和 取向产生的两种旋转异构体的存在一致。在MP2/cc - pVTZ水平上进行的计算用于估计观察到的三种旋转异构体的平衡几何结构。通过观察每种物质自然丰度下八个次要同位素异构体（碳和氧）的转动跃迁，证实了它们的归属。使用实验测定的转动常数推导的质量相关结构与估计值相比具有优势。所得的几何参数集表明，芳环主链因引入角形甲氧基取代基而扭曲，有在环周围引起键长交替的趋势，并且受到氟的吸电子效应影响。
