The synthesis of 2-(4-methyphenyl)benzimidazole from 4-methyl benzylaldehyde and o- phenylenediamine was performed. The reaction process was monitored by HPLC, and the structures of related intermediates and products were identified by ¹H NMR, FT-IR and LC-MS techniques. The experiments proved that mono-Schiff base and bis-Schiff base could both be synthesized at the same time when o- phenylenediamine and aldehydes were in a molar ratio of 1∶1, and the influences of the reaction were proposed.

Key words: aldehyde, o-phenylenediamine, benzimidazole derivative, reaction mechanism