Practical Experiment 1: Benzimidazole from orthophenylene diamine

Benzimidazole from orthophenylene diamine

1. Experiment 1 To synthesize and characterized Benzimidazole from Orthophenylene diamine (OPD). Presented By…. Prof. Sonali R. Pawar Medicinal Chemistry I B. Pharmacy IV semester

2. Expt. No. Title of the Experiment 01 To synthesize and characterized benzimidazole from orthophenylene diamine (OPD). 02 To synthesize and characterized Benztriazole. 03 To synthesize and characterized Ethyl p- amino benzoate (Benzocaine) from p-amino benzoic acid. 04 To synthesize and submit Benzyl from benzoin. 05 To synthesize and characterized Phenytoin. 06 To synthesize and characterized 2,3- diphenyl quninoxaline from orthophenelene diamnine (OPD). 07 To synthesize and characterized phenothiazine from diphenylamine. 08 To study of column chromatography techniques for separation and purification of organic of organic compound. 09 To perform column chromatography techniques for separation and purification of organic of organic compound of given sample. 10 To determine partition coefficient of benzoic acid between benzene and distilled water. 11 To determine partition coefficient of Iodine between distilled water and carbon tetra chloride. 12 To determine partition coefficient of boric acid between benzene and distilled water. 13 To determine buffer capacity and dissociation constant Pka of the monobasic acid. 14 To determine buffer capacity and dissociation constant Pka of the dibasic acid. 15. To determine buffer capacity and dissociation constant Pka of the tribasic acid.

3. Benzimidazole  is a heterocyclic aromatic organic compound . This bicyclic compound consists of the fusion of benzene and imidazole. It is a colorless solid . Benzimidazoles are often bioactive . Many  anthelmintic drugs (albendazole, mebendazole, triclabendazole etc.) Belong to the benzimidazole class of compounds.  Benzimidazole fungicides are commercialized. They act by binding to the fungal microtubules and stopping hyphal growth . It also binds to the spindle microtubules and blocks nuclear division. Benzimidazole

4. Aim:- To prepare a & submit Benzimidazole from o- phenylenediamine . Requirement :- Apparatus:- Round bottom flask, Beaker, Measuring cylinder, Water bath, Buchner funnel. Chemicals :- O- phenylenediamine , Formic acid (90 %), NaOH (10%). Principle:- The synthesis Benzimidazole is affected by simply heating the o- phenylenediamine & formic acid together (condensation type of reaction ).

5. Place 2.7gm of the o- phenylenediamine in a round bottomed flask of 250 ml & add 1.6 gm (16ml) of 90 % formic acid. Heat the mixture on a water bath at 100 C for 2 hr. Cool & add 10 % sodium hydroxide solution slowly, with constant rotation of the flask, until the mixture is just alkaline to litmus. Filter off the synthesized crude Benzimidazole by using the pump, cold water. Procedure

6. Dissolve the synthesis product in 400 ml of boiling water , Add 2 gm of decolorizing carbon & digest for 15 min Filter rapidly through a Buchner funnel & a flask at the pump. Cool the filtrate to about 10 C, filter off the Benzimidazole, Wash with 25 ml of cold water & dry at 100 C. The yield of pure Benzimidazole is 25 gm (85%). M.p . 171-172 C. Recrystalisation

7. Reaction

8. Calculation Here limiting reagent is o- phenylenediamine ; hence yield should be calculated from its amount taken. Molecular formula of o- phenylenediamine forms = C 6 H 8 N 2 . Molecular formula of Benzimidazole = C 7 H 6 N 2 . Molecular weight of o- phenylenediamine = 108 g/mole. Molecular weight of Benzimidazole = 118 g/mole.

9. Theoretical yield:- 105 g o- phenylenediamine forms 118 g Benzimidazole Therefore, 2.7 g o- phenylenediamine will from …. (X) g Benzimidazole X = ( 118x2.7 )/108 = 2.95 g Theoretical yield = 2.95 g Practical yield = 2.91 g % yield = (Practical yield) x 100 =2.91/2.95 =98.64% (Theoretical yield) Theoretical yield

10. Benzimidazole was synthesized from o- phenylenediamine & submitted. Result Name of Compound Benzimidazole Theoretical yield 2.95 Gm Practical yield 2.91Gm % Practical yield 98.64 % Melting point 170-175 C Synthesis, Characterization, and Biological Evaluation of Benzimidazole Derivatives as Potential Anxiolytics (nih.gov)

11. Which acid is used in synthesis of Benzimidazole? Ans.: Formic acid is used in synthesis of Benzimidazole. What are the uses of Benzimidazole? Ans.: Used as antitumor, antifungal, antiparasitic , antiviral, analgesics, antihistamine, as well as used in cardiovascular disease, neurology and ophthalmology. What is the principal of synthesis of Benzimidazole? Ans.: The synthesis of Benzimidazole is affected by simply heating the o- phenylenediamine and formic acid together (condensation type of reaction). Viva Voce