Carboxylic acids with phenolic function. Periodic acids (aromatic) containing acidic group and hydroxyl group

Carboxylic acids with phenolic function, esters, salts and other derivatives:
The acids - phenols are periodic acids (aromatic) containing simultaneously the acidic group (COOH) and the group of hydroxyl (OH) or more in the nucleus, so the simplest acid - phenol has the following symbolic group (OH. C6H4 COOH).