Department of Chemistry, King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabia.
Spectrochim Acta A Mol Biomol Spectrosc. 2011 Mar;78(3):1162-7. doi: 10.1016/j.saa.2010.12.070. Epub 2010 Dec 25.
The structural stability of phenylacetic acid and mandelic acid was investigated by the DFT-B3LYP and the ab initio MP2 calculations with the 6-311G** basis set. The two molecules were predicted at the DFT and MP2 levels of calculation to have the non-planar (Np) forms as their lowest energy structures. The observed spectral intensities of the acids were consistent with the Np conformation being the predominant form at room temperature. The vibrational wavenumbers were computed at the B3LYP level of theory and tentative vibrational assignments were provided on the basis of combined theoretical and experimental infrared and Raman data of the molecules. The sharpness of the methylenic O-H stretching mode in the IR spectrum of mandelic acid suggests the absence of intermolecular dimerization in the acid which is supported by the observation of no splitting of its CO stretching mode.
通过 DFT-B3LYP 和 ab initio MP2 计算与 6-311G**基组，研究了苯乙酸和扁桃酸的结构稳定性。这两个分子在 DFT 和 MP2 计算水平上被预测为具有非平面（Np）形式作为其最低能量结构。在室温下，观察到的酸的光谱强度与 Np 构象是主要形式一致。在 B3LYP 理论水平上计算了振动波数，并根据分子的红外和拉曼数据的理论和实验结合提供了暂定的振动分配。扁桃酸红外光谱中亚甲基 O-H 伸缩模式的尖锐性表明酸中不存在分子间二聚化，这得到其 CO 伸缩模式没有分裂的观察结果的支持。
