Ortho substituted Benzoic acid is more acidic then meta or para substituted benzoic acid irrespective of nature of group . Such group creates steric strain resulting in rotation of the carboxylic group and shifting it out of plane of the benzene ring and the carboxylic group can no longer participate in ring resonance and thereby the acidity increases as delocalization of negative charge equally on the both oxygen atom of conjugate base ( carboxylate ion) .It is also called Ortho effect. Note: However for smaller or linear groups like -NH2 or -OH or �CN , SIR effect not applicable.