School of Chemistry, Monash University, Clayton, Victoria 3800, Australia.
J Chem Phys. 2013 Jan 14;138(2):024303. doi: 10.1063/1.4773347.
The structures of three simple aromatic carboxylic acids: benzoic, isophthalic, and terephthalic have been investigated using a combination of theoretical high-level quantum chemical calculations and experimental millimeter-wave Stark-modulated free-jet absorption spectroscopy. Rotational and centrifugal distortion constants have been measured for one conformer of each of the species and for its -COOD isotopologue, leading to the experimental determination of the coordinates of the carboxyl hydrogen atom. Consideration of the observed inertial defect is consistent with a planar equilibrium structure for each species. Calculated structures, relative energies, and electric dipole moments, using ab initio methods at the MP2/cc-pVTZ level, are reported for all the lower-energy conformers of each species. The theoretical calculations lead to the unambiguous identification of the conformers involved in the observed microwave spectra. The match between theoretical and spectroscopic measurements was used to gauge the reliability of the quantum chemical structure optimization calculations.
苯甲酸、间苯二甲酸和对苯二甲酸，使用理论上的高级量子化学计算和实验性毫米波 Stark 调制自由喷射吸收光谱学的组合进行了研究。已经为每种物质的一个构象体及其 -COOD 同位素测量了旋转和离心畸变常数，从而实验确定了羧基氢原子的坐标。对观察到的惯性缺陷的考虑与每个物质的平面平衡结构一致。使用 MP2/cc-pVTZ 水平的从头算方法，报告了每种物质的所有低能构象体的计算结构、相对能量和电偶极矩。理论计算明确确定了参与观察到的微波光谱的构象体。理论和光谱测量之间的匹配用于衡量量子化学结构优化计算的可靠性。
