4,4'-Dimethylbiphenyl is used in the preparation of biphenyl-4,4?-dicarboxylic acid, which acts as a monomer utilized in the synthesis of linear long chain polymer through polycondensation reaction. It is used to prepare 4-(4'-methylphenyl)benzaldehyde by selective photoxygenation reaction using 9-phenyl-10-methylacridinium perchlorate as a catalyst under visible light irradiation.
