Page 15 - Practical-workbook-organic-3 isa

Procedure of Benzimidazole Synthesis

In a 250 ml stoppered flask:

◼ Add o-phenylenediamine (1.08 g) then formic acid (0.8 ml).

◼ Shake the flask well to mix the 2 components.

◼ Attach the condenser, then heat the mixture in a water bath at 90°C for 30 min.

◼ Cool the reaction mixture at room temperature.

◼ Add 10% NaOH solution dropwise with shaking until a buff ppt is formed; to

neutralize the excess acid and alkalinize the reaction mixture then a buff precipitate

of benzimidazole is formed.

◼ To purify the product:

1. Wash with water (100 ml) to eliminate unreacted formic acid.

2. Filter out the produced benzimidazole.

14