Synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzo[d]imidazoles by the reaction of o-phenylenediamine with substituted aromatic aldehydes in the presence of 1-heptanesulfonic acid sodium salt(10mol%)at room temperature.The reactions were performed in acetonitrile:water(8:2).The method was proved to be eco-friendly,convenient and the products were isolated with good yields(82- 90%). Synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzo [d] imidazoles by the reaction of o-phenylenediamine with substituted aromatic aldehydes in the presence of 1-heptanesulfonic acid sodium salt (10 mol% The reactions were performed in acetonitrile: water (8: 2). The method was proved to be eco-friendly, convenient and the products were isolated with good yields (82-90%).