The strength of a carboxylic acid depends on the extent of its ionization constant: the more ionized it is, the stronger it is. As an acid becomes stronger, the numerical value of its acid dissociation constant| drops.
In acids, the electron-releasing inductive effect of the alkyl group increases the electron density on oxygen and thus hinders the breaking of the O-H bond, which consequently reduces the ionization. Due to its greater ionization, formic acid () is stronger than acetic acid (). Monochloroacetic acid (), though, is stronger than formic acid, due to the electron-withdrawing effect of chlorine promoting ionization.
In benzoic acid, the carbon atoms which are present in the ring are sp hybridised. As a result, benzoic acid () is a stronger acid than cyclohexanecarboxylic acid (). Also, in aromatic carboxylic acids, electron-withdrawing groups substituted at the ortho and para positions can enhance the acid strength.
Since the carboxyl group is itself an electron-withdrawing group, dicarboxylic acids are, in general, stronger acids than their monocarboxyl analogues.
The Inductive effect will also help in polarization of a bond making certain carbon atom or other atom positions.