摘要
采用pH电位滴定法及分光光度法测定了单宁酸化合物1,2,3,4,6-O-五没食子酰葡萄糖(PGG),及其组成单体化合物没食子酸甲酯(MeG)在溶液中的去质子化特性,运用化学计量学软件Reactlab Equilibrium测定了相应的离解常数,分析了不同pH值条件下各化合物的存在形式及变化规律。研究结果表明:随着pH值的升高,PGG逐渐发生去质子化反应脱去质子,pH>11时,配体失去全部质子。光谱学研究发现PGG分子中共有两个酚羟基依次发生了去质子化,形成氧负离子,并进一步与金属离子发生络合,离解常数分别为pKa1=10.84±0.03和pKa2=10.62±0.02;MeG分子中只有一个酚羟基会发生去质子化反应,其离解常数为pKa=9.68±0.02。
The deprotonation process of a typical tannic acid,1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose(PGG),and its parent compound methyl gallate(MeG)was studied by pH potentiometric titration and spectrophotography.The dissociation constants of PGG and MeG were calculated by chemometric methods using the Reactlab Equilibrium software.Concentration profiles of the fully protonated PGG and its two deprotonated forms at different pH values were also predicted by the chemometric method.The results showed that the deprotonation of phenolic hydroxyl of PGG was found with the increasing of pH value,and fully deprotonated forms of PGG existed at pH>11.These formed negative ions of oxygen can further coordinate with metal ions.Spectroscopic studies showed that there were two deprotonated forms of PGG,and the corresponding p K a values were 10.84±0.03 and 10.62±0.02.There was only one deprotonated form of MeG during titration,and the corresponding p K a value was 9.68±0.02.
作者
张亮亮
张禾
徐曼
胡新宇
刘义稳
ZHANG Liangliang;ZHANG He;XU Man;HU Xinyu;LIU Yiwen(Institute of Chemical Industry of Forest Products,CAF,National Engineering Lab.for Biomass Chemical Utilization,Key Lab.of Chemical Engineering of Forest Products,National Forestry and Grassland Administration,Key Lab.of Biomass Energy and Material,Jiangsu Province,Jiangsu Co-Innovation Center for Efficient Processing and Utilization of Forest Resources,Nanjing 210042,China;Wufeng Chicheng Biotechnology Co.Ltd.,Engineering Techonology Research Center of High-Efficient Cultivation and Deep Processing of Chinese Gall,National Forestry and Grassland Administration,Yichang 443413,China)
出处
《林产化学与工业》
EI
CAS
CSCD
北大核心
2021年第1期1-6,共6页
Chemistry and Industry of Forest Products
基金
国家重点研发计划资助项目(2018YFD0600404)。
关键词
单宁酸
去质子化
离解常数
分光光度法
化学计量学
tannic acid
deprotonation
dissociation constants
spectrophotography
stochiometry
