1、 Structural characteristics of benzoic acid and p-methyl benzoic acid

　　The molecular formula of benzoic acid is c6h5ch2cooh, which is an aromatic carboxylic acid with benzene ring and carboxyl group. The molecular formula of p-methylbenzoic acid is C8H8O2, which is a styrene carboxylic acid containing methyl substituents, including benzene ring, methyl group and carboxyl group.

　　2、 Comparison of acidity between benzoic acid and p-methyl benzoic acid

　　Both benzoic acid and p-methyl benzoic acid are organic acids containing carboxyl groups and are acidic. The acidity of carboxyl group is related to the Ionizability of OH ions in carboxyl group. The more easily ionized, the stronger its acidity.

　　In benzoic acid and p-methyl benzoic acid, the carboxyl group of benzoic acid is easier to release h+ ions than that of methyl benzoic acid, so the acidity of benzoic acid is stronger than that of p-methyl benzoic acid.