Friday , 25 September 2020


About author:
Ramesh Dhani
Dept. of Pharmaceutical Chemistry
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Recently in benzimidazole chemistry has been revived somewhat by the discovery that the 5,6-dimethyl benzimidazole moiety is a part of the chemical structure of vitamin B12.The benzimidazoles are also known as benziminazolones or benzoglyoxalines.The new benzimidazole derivative i.e, 2-mercapto benzimidazole was synthesized.The melting point was detected by capillary tube method and the purity of the comound was cheked by TLC, here the solvent system was [hexane: ethyl acetate (1:3)] used and further the compound characterized by IR spectral studies.
Key words: Benziminazolones, 2-mercapto benzimidazole, O-Phenylenedimine,  Ethanol, Ethyl Chloro Acetate
Numerous heterocyclic compounds, cyclic anhydrates, cyclic imides, cyclic acetals of dihydroxy alcohols, the solvents, dioxanes and tetrahydrofuran, in all of these, the chemistry is essentially that of their open-chain analogues.The benzimidazole contains a phenyl ring fused to an imidazole ring, as indicated in the structure of benzimidazole. The important group of substances has found practical application in a number of fields. Recently in benzimidazole chemistry has been revived somewhat by the discovery that the 5,6-dimethyl benzimidazole moiety is a part of the chemical structure of vitamin B12. The benzimidazoles are also known as benziminazolones or benzoglyoxalines. They have been named also as derivatives of o-phenylene diamines. Benzimidazole which contain a hydrogen atom attached to nitrogen in the 1-position readily tautamerise.
Sang yon cho, synthesized a series of benzimidazole derivatives containing oxycyclic pyridine and evaluated for their gastric H+/ K+-ATPase inhibitory activity. Several of the synthesized compounds exhibited potent anti-secretion in pylorus ligated rats when administered intra duodenal and their inhibitory activities were compared with the standard Omeprazole. Keiji Kubo, synthesized many 2-[4-fluro alkoxy-2-pyridyl) methyl] sulfynyl]-1H-benzimidazoles and tested for anti-secretary, anti-ulcer and cytoprotective activities. Most of these compounds were superior to Omeprazole in anti-secretary and anti-ulcer potencies and especially in protecting the gastric mucosa from ethanol induced damage.G.L.Dunn et. al., synthesized a series of  new benzimidazoles, benzoxazoles and benzothiazoles of nitrothiophene and nitro pyrrole and  reported very potent inhibitors.
Preparation of 2-mercapto benzimidazole :
A mixture of 10.8gm (0.1mole) of o-phenylenediamine, 5.65 gm (0.1mole) of potassium hydroxide and 7.67 gm (0.1mole, 6.19ml) of carbon disulfide, 100ml of 95% ethanol and 15 ml of water was taken  in  a 500ml round bottom flask heated under reflux for three hours. Then 1-1.5 gm of charcoal was added cautiously and the mixture is further heated at the reflux for 10 minutes, the charcoal is removed by filtration. The filtrate is heated to 60-70oC, 100ml of warm water is added, and acidified with dilute acetic acid with good stirring. The product separated as glistening white crystals, and the mixture is placed in a refrigerator for three hours to complete the crystallization. The product is collected on a Buckner funnel and dried over night at 40oc.
From the literature survey it reveals that benzimidazoles and 2-mercapto benzimidazoles have been reported for spectral studies. Synthesized benzimidazole derivatives further studied for characterization of IR. The following functional groups are observed NH-benzimidazole at Wave number 3088 cm-1, Ar-CH at 2982 cm-1, NH- at 1640 cm-1. The dried product is recrystallised by ethanol the yield is 8.5gm (73%) melting point is 300-305oC.
From the above study concludes that all substituted benzimidazle derivatives like 2-mercapto benzimidazoles molecule was conformed form the IR spectral studies. The purity of the compound was cheked by TLC, solvent system was [hexane: ethyl acetate (1:3)]. The melting point( M.P) of 2-mercapto benzimidazoles was detected.


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