文献类型：期刊文献

英文题名：Deprotonation Mechanism of Methyl Gallate: UV Spectroscopic and Computational Studies

作者：Zhang, Liangliang[1] Liu, Yuchen[1] Wang, Yongmei[1]

第一作者：张亮亮

通信作者：Zhang, LL[1]

机构：[1]Chinese Acad Forestry, Inst Chem Ind Forest Prod, Nanjing 210042, Jiangsu, Peoples R China

年份：2018

卷号：19

期号：10

外文期刊名：INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES

收录：;Scopus(收录号：2-s2.0-85054898252);WOS:【SCI-EXPANDED(收录号:WOS:000448951000266)】；

基金：This work was financially supported by National Key R&D Program of China [grant number: 2018YFD0600404].

语种：英文

外文关键词：methyl gallate; polyphenol; tannins; pH titration; spectroscopic method

摘要：In the present paper, methyl gallate (MeG), a simple polyphenol and also the monomer of hydrolysable tannins, was selected to study the deprotonation process for the hydroxyls of the galloyl group by the combined use of spectroscopic measurements and quantum chemical calculations. The results of quantum chemical calculations show that the deprotonated form of methyl gallate undergoes the para-quinoid localization in the benzene ring, compared with free methyl gallate. The predicted spectra obtained from the free and deprotonated methyl gallate models are in agreement with the experimental UV-visible (UV-vis) absorption spectra. In the same way, the vibrational spectra of the para-quinoid MeG models validate the proposed mechanism of the deprotonation of MeG molecule. The pH influence on the deprotonation reaction and oxidization of phenolic groups has been also investigated. The pK(a) values of MeG were evaluated using the chemometric modeling method. The first acid dissociation constant (pK(a1)) for MeG was evaluated to be 4.20 +/- 0.01, and the second one (pK(a2)) was 10.78 +/- 0.06.