Procedure for the synthesis of benzimidazole prepared by Harshitha B N

1. TUMKUR UNIVERSITY
TUMAKURU
“PROCEDURE FOR SYNTHESIS OF BENZIMIDAZOLE”
Prepared By
HARSHITHA B.N
Ⅱ M.Sc. Ⅳ Semester
Department of Studies and Research in Organic Chemistry
Tumkur University, Tumakuru
Under the Guidance
Dr. G. KRISHNASWAMY
Faculty
Department of Studies and Research in Organic Chemistry
Tumkur University, Tumakuru 1

2.  AIM : To synthesize Benzimidazole from O-phenylenediamine.
 PRINCIPLE : Benzimidazole is a (6+5) heterocyclic aromatic compound formed by the
fusion of the benzene and imidazole moiety. Benzimidazole resemble Purine like structure
and elicit some biological application. It exists in two tautomeric forms.
 Well known active drugs with Benzimidazole ring are Albendazole and Mebendazole used
as anthelmintic drugs.
 Simplest method for the synthesis of Benzimidazole is condensation of O-
phenylenediamine (OPD) and formic acid.
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3.  CHEMICALS REQUIRED : 1. O-phenylenediamine
2. 90% Formic acid
3. Sodium Hydroxide.
 APPARATUS REQUIRED : 1. Round bottom flask or Iodine flask
2. Condenser
3. Filtering funnel
4. Filter paper.
 PROCEDURE:-
 In a round bottom flask , 1 g of O-phenylenediamine is treated with 3.48ml of 90%
formic acid.
 The resulting mixture was heated in a water or sand bath at 100OC for 2hours.
 After completion , cool the reaction mixture to lab temperature and add slowly 10%
sodium hydroxide solution with thorough mixing until the mixture is just alkaline to red
litmus.
 The Crude Benzimidazole obtained was collected by filtration and rinsed with cold water.
 The pure product was obtained by recrystallization in hot water. 3

4.  REACTION :
 CALCULATION :-
 THEORETICAL YIELD :
 108.13g of O-phenylenediamine yields 118.4g of Benzimidazole.
 1g of O-phenylenediamine will forms X g of Benzimidazole.
AMOUNT MOLECULAR
WEIGHT
MOLES EQUIVALENT
1. OPD 1g 108.1 0.00925 1
2. HCOOH 3.48ml 46.03
d=1.22g/ml
0.00925 10
3. 10%NaOH 10g in 100ml water
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5. 100
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6.  REPORT :
 APPLICATIONS :
 The Benzimidazole and its derivatives play a very important role as a therapeutic agent.
For Example: Antiulcer and Anthelmintic drugs.
 The Benzimidazole derivatives exhibit pharmacological activities such as antimicrobial,
antiviral, anticancer, anti-inflammatory, analgesic etc.
STRUCTURE
and NAME
THEORETICAL
YIELD
PRACTICAL
YIELD
%
YIELD
MELTING POINT
(Theoretical)
MELTING POINT
(Practical)
BENZIMIDAZOLE
1.09g 0.78g 71.4% 171 – 172 OC 170 OC
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