The Electronic Structure Studies of Hydroxyl Substituted Benzoic Acids

Abstract

The electronic structure of various hydroxyl substituted benzoic acids is studied by using ab initio method at HF/6-31G* level. The importance was put on the charge distribution on benzene ring and the effect of hydroxyl group. The total negative charge on benzene ring is in inverse proportion to the number of hydroxyl substituents. The net charge change on carbon atoms of benzene ring of multi-hydroxyl benzoic acids induced by hydroxyl is very close to the simple addition of that of corresponding mono-hydroxyl benzoic acids. These phenolic acids possess one to three active sites on benzene ring where the negative charges are much more than that of other sites and than that of unsubstituted benzoic acids. The relationship of electronic structure and reactivity of the compounds is discussed. The lower decarboxylation temperature is found to be well correlated with the more negative charge on the carbon atom linked to carboxyl group for most of the measured phenolic acids.