Synthesis of Benzimidazole

 

Aim: To prepare and submit Benzimidazole from o-phenylenediamine.

Apparatus: 

• Beaker
• Conical flask
• Measuring jar
• Water Bath 

Principle: The principle involved in the synthesis of Benzimidazole is Philips reaction involves the condensation of ortho phenylemediamines with organic acids in presence of dilute minerale acid to furnish Benzimidazoles.

Mechanism: Initially one of the amino groups is acylated with the organic acid in presence of mineral acid to furnish an N-acylated compound. In the next step, the other nitrogen is also acylated by making bond with the carbonyl carbon of the first acyl group leading to ring closer.

 

Procedure: Place 27g of o-phenylenediamine in 250 ml RBF and add 16ml of 90% formic acid. Heat the Mixture on Water bath  at 100 c for 2 hrs. Cool, add 10% sodium hydroxide solution slowly, with constant rotation of the flask, Until the mixture is just alkaline to litmus. Filter off the solid benzimidazole at the pump and wash with the little cold water. Recrystallize from  hot water and dry upon hot air oven or in the air.

Calculation:

108gm of o-phenylenediamine =118gm of Benzimidazoles.

27gm of o-phenylediamine = (x) gm of Benzimidazoles.

X = (118 X 27)/108 = 29.5g

Theoretical yield =29.5gm

Practical Yield = -------- gm

% purity =(Practical yield/Theoritical yield) X 100

               

Report: The Benzimidazole was prepare and submitted in the laboratory its percentage yield was found to be -----%

Category: Anti fungal.