I have recently done an experiment where I synthesised benzimidazole using o-phenylenediamine, formic acid (90%) and NaOH (10%). I'll add my experimental below so that everyone knows exactly what it is I did. I got a low yield at the end of the experiment and I was told by my lecturer that there must be a major influence that caused such a low yield apart from the obvious reasons (Human error, losses during transfer from glassware, heating and cooling issues during recrystallisation and purification...etc). I was wondering if anybody had an idea what could cause such a low yield? I did not make any major errors when carrying out the experiment so I do know what other reasons there could be.
Thanks in advance for helping Experimental
O-phenylenediamine (5.4 g, 50 mmol) and formic acid (90 %, 3.2 mL, 3.46 g, 75 mmol) was heated under reflux for 1.5 hours. To the cooled reaction mixture, water (10 mL) and NaOH (10 %) was added until alkaline pH persisted. Pale orange precipitate was formed and filtered under suction. Activated carbon (0.2 g) and water (75 mL) was added to the crude benzimidazole and heated under reflux to a simmer. Reaction mixture was filtered hot and then cooled to 10-15oc. The precipitate was filtered then dried in oven for 15 minutes. Benzimidazole seen as white crystals (1.785 g, 21 %) Melting Point: (165 - 167oc)