ABSTRACT:
Benzimidazole is a heterocyclic aromatic organic compound. In step-1, The O-pheylenediamine (13.5 gm and 0.12mol) was placed in a 250 ml round-bottomed flask and 85 percent formic acid (9.2 gm, 8.4 ml and 0.17 mol.) was added to it. The mixture was heated on a water bath for 100oC for 3 hours. The mixture was cooled, 10 percent sodium hydroxide solution was added slowly, with constant rotation of the flask, until the mixture is just alkaline to litmus. In step-2, the mixture of o-pheylenediamine dihydrochloride (5.43 gm and 0.03 mol.), 20 ml of water, acetic acid (5.4 gm, 5.67ml, and 0.09 mol.) was refluxed for 4 hours. The reaction mixture was cooled and basified with gradual addition of concentrated ammonia solution, the precipitate was filtered, dried and recrystallised from 10 % aqueous ethanol. In step-3, the mixture of O-pheylenediamine dihydrochloride (5.43 gm and 0.03 mol.), 20 ml of water, phenyl acetic acid (12.3 gm, 0.09 mol.) was refluxed for 6 hours. The reaction mixture was cooled and basified with gradual addition of concentrated ammonia solution, the precipitate was filtered, dried and recrystallised from 40% aqueous ethanol.