Azeotropic Preparation of a C-Phenyl N-Aryl Imine: An Introductory Undergraduate Organic Chemistry Laboratory Experiment

Imines are important in biological chemistry and as intermediates in organic synthesis. An experiment for introductory undergraduate organic chemistry is presented in which benzaldehyde was condensed with p-methoxyaniline in toluene to give 4-methoxy-N-(phenylmethylene)benzenamine. Water was removed by azeotropic distillation using a Dean-Stark trap. The reaction was readily performed in one 3 h laboratory period, gave a crystalline product, and was easily followed visually by the amount of water collected. It demonstrated important concepts from second-year undergraduate organic chemistry, including equilibrium processes, condensation reactions, and imine formation. The experiment also gave students exposure to important laboratory techniques including azeotropic distillation, use of a water trap, and mixed-solvent recrystallization.