 The carboxylate anion (R–COO− or RCO2−) of a carboxylic acid is usually named with the suffix "-ate", in keeping with the general pattern of "-ic acid" and "-ate" for a conjugate acid and its conjugate base, respectively.For example, the conjugate base of acetic acid is acetate.Carbonic acid, which occurs in bicarbonate buffer systems in nature, is not generally classed as one of the carboxylic acids, despite that it has a moiety that looks like a COOH group.