Here in we report a green and efficient synthesis of benzimidazoles and its derivatives, by the condensation of 1,2-phenylendiamine and orthoesters in presence of ionic liquid, 1-butylimidazolium bisulphate [Hbim][HSO4] as a catalyst and water as solvent. The synthesis highlights a comparative study of conventional, ultrasound and microwave techniques. The products obtained in good to moderate yields with simple work up procedure. The compound 3c was investigated in vitro against Gram +ve and Gram –ve bacteria at different concentrations and compared with standard drug ciprofloxacin.