Study of citronellal condensation reactions with 1,2-phenylenediamine by CuSO4 Catalyst under Microwave Irradiation

Abstract

Benzimidazole compounds were prepared from the condensation reaction between 1,2-phenylenediamine and citronellal. In all cases, the condensation reaction is very selective and simple method under microwave conditions. The reaction takes place efficiently in ambient conditions with good results. Citronellal was used as the starting material for the synthesis of benzimidazoles because of their antibacterial activity. The strength of benzimidazole activity not only influenced by its main ring but also by the presence of substituents that bound to imidazole or aromatic ring. In this work, the purification of citronellal from kaffir lime oil was conducted by using salt reaction with NaHSO3 saturated solution and hydrolysis by NaOH saturated solution. The synthesis reaction proceeds using CuSO4 catalyst in dichloromethane as a solvent with mole ratio variation of 1,2-phenylenediamine to citronellal, 1:2, 1:3, 1:4, and 1:5, respectively. The optimum reaction was obtained at 1:2 and 1:3 mole ratio of citronellal. The yield of the product is 5.76 % and 5.097 % (m.p 140-143°C). FTIR analysis showed spectrum bands for C=N at 1671 cm-1 and C-N 1269 cm-1. Characterization was carried out using MS and showed that the synthesized product had a molecular weight m/z: 243, 381 and 453. Analysis result from FTIR, mass spectrometry and melting point indicated the product of benzimidazole derivatives was successfully obtained in this study.