N bromosuccinamide reagent

synthesis reagent and their application

1. N-BROMOSUCCINIMIDE PRESENTED BY PRANJAL TIDKE M. PHARM 1 ST YR

2. N-BROMOSUCCINIMIDE N- B romosuccinimide is a chemical reagent used in radical substitution and electrophilic addition reaction in organic chemistry NBS can be a convenient source of the bromine radical (Br•) DESCRIPTION IUPAC name: 1Bromo-2,5 pyrrolidinedione Other name : N- bromosuccinimide (NBS) Chemical formula : C4H4BrNO2 Molecular mass : 177.99g/ mol Appearance : white solid Melting point : 175-178 Solubility : soluble in water soluble in CCl4 at 25 C, hexane

3. PREPARATION : It is a very important derivative of succinimide and can be conveniently prepared by adding bromine to an ice-cooled solution of succinimide in alkali. A precipitate of N- Bromosuccinimide is immediately obtained

4. APPLICATIONS As a brominating agent : NBS was introduced by Zielger in 1942 as selective brominating agent because it normally brominates the ethylenic compounds in the allylic position It is also used for benzylic bromination Examples:

5. MECHANISM : It is believed that the main function of NBS is to act simply as a bromine reservoir maintaining a lower concentration of molecular bromine by undergoing reaction with HBr which is initialy formed in the side reaction . INITIATION T he bromine molecule then gets dissociated into bromine atoms in the presence of light or radical initiators PROPOGATION:- Bromine atom then abstracts hydrogen forming an allylic radical which then reacts with the molecular bromine to form the product .

6. Applications of allylic bromination Preparation of bromoacid ester W hen NBS reacts with methyl crotonate , there occurs the formation of 3-bromocrotonate which as synthetic reagent found in Reformatsky reaction . e.g. in the synthesis of vit . A

7. Conversion of vit . A1 To vit . A2 NBS has been fount to be of immense help in the conversion of vit . A1 to vit . A2 Allylic bromination by NBS also finds uses in the synthesis of some important organic natural product such as reserpine, colchicine, patuline .

8. A llylic bromination of cholesteryl benzoate at C17 find use in the commercial production of vit.D3 A llylic bromination is also used for converting a monosaturated compound into diene and triene 2. As an oxidizing agent NBS is also used for oxidizing primary alcohol and primary amines To aldehydes, and secondary alcohol to ketone. C2H5OH + > NBr CH3CHO +>NH + HBr

9. CH3.CH(NH2).COOH NBS CH3CHO + CO2 + NH3 Alanine acetaldehyde 3. Miscellaneous reactions NBS in aqueous solution decarboxylates α -amino acids , peptides and proteins

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