Substituent Effects on the Low-Frequency Vibrational Modes of Benzoic Acid and Related Compounds

• Published in: Chinese journal of chemistry Vol. 25; no. 3; pp. 272 - 277
• Main Author: 葛敏 赵红卫 王文锋 余笑寒 李文新
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.03.2007; WILEY‐VCH Verlag
• Subjects: benzoic acid; DFT; substituent effect; terahertz time-domain spectroscopy; 低频振荡模; 光谱性质; 取代效应; 生物分子; 相关化合物; 苯甲酸
• ISSN: 1001-604X; 1614-7065
• DOI: 10.1002/cjoc.200790054

Well-resolved absorption spectra of benzoic acid and its derivatives with one hydrogen atom replaced by a substituent group CH3, OH, NH2 or NO2 were reported in the frequency region between 6 and 67 cm^-1 at room temperature with terahertz time-domain spectroscopy （THz-TDS）. These substances can be distinguished easily based on the terahertz absorption spectra. The measurements suggested that even minor changes in the molecular configuration and chemical composition lead to distinct differences in THz spectrum. Density functional theory （DFT） method was used to assist the analysis and assignment of the individual THz absorption spectra of benzoic acid and its methyl derivatives. Observed THz responses of samples can be assigned to the collective vibrations associated with intermolecular hydrogen bonds.