Properties of Carboxylic AcidsIt is clear from the name that carboxylic acids are acidic. The hydrogen of the carboxyl group (-COOH) is acidic. The strength of these acids can be explained in terms of the relative stabilities of their conjugate bases. Weaker the conjugate base is, the stronger the acid. Keep in mind the fact that carboxylic acids are weak acids.
βThe acidity of a carboxylic acid is influenced by its substituents. Substituents which are very electronegative, especially when they are attached to the a-carbon, increase the acidity of carboxylic acids. As the number of electronegative substituents increases, so does the acidity. This increase in acidity is because of the increased stability of the carboxylate ion formed, as a result of the presence of the electronegative substituent. This effect is due to what is known as inductive effect. Because of the electron withdrawing effect of the substituent, the charge is dispersed and the ion (carboxylate ion) is stabilized. Study the following gradation of increasing acidity to reinforce the point just made.
Carboxylic acids can undergo extensive hydrogen bonding. So they have higher boiling points than alkanes or even alcohols. Carboxylate ions are resonance stabilized. The negative charge in the carboxylate anion is shared by both the oxygens.