N-Bromosuccinimide

Description

N-Bromosuccinimide (NBS) is a reagent typically used in radical substitution and electrophilic addition reactions. In pure form it exists as a white solid but over time it will decompose to give off bromine which will give it a slight yellow/brown color.

Chemical properties

white to light yellow crystalline powder

The Uses of N-Bromosuccinimide

N-Bromosuccinimide is a brominated succinimide used as a chemical reagent in radical substitution and electrophilic addition reactions in organic synthesis.

The Uses of N-Bromosuccinimide

To a solution of the SM (80 g, 0.27 mol) in CHCl3 (1 L) at 10-15 C was added dropwise a solution of Br2 (16 mL, 0.31 mol) in CHCl3 (100 mL). The reaction was stirred at 12 C for 10 min, then washed sequentially with cooled sat aq NaHCO3 (2 x 500 mL) and sat aq brine (400 mL), dried, and concentrated in vacuo. Crystallization of the residue from EtOAc provided the product as a yellow solid. [90 g, 88%]

What are the applications of Application

N-Bromosuccinimide is used in radical substitution and electrophilic addition reactions.

It can be used as a reagent:
In the Wohl-Ziegler reaction (bromination at allylic positions via a radical pathway).
To synthesize benzils and aliphatic 1,2-diketones from hydrobenzoins and 1,2-diols in the presence of CCl4 as a solvent.
To prepare tricyclic azepino[4,5-b]indoles from indole-β-enaminoesters or β-enaminones via Pictet–Spengler cyclization.
To synthesize acylsilanes via oxidative hydrolysis of 2-silyl-1,3-dithianes.
Versatile brominating agent. For the oxidation of tryptophan though tyrosine, histidine and methionine residues may be oxidized to a lesser extent. Also used for the modification of ribosomal sulfhydryl groups.

Definition

ChEBI: N-bromosuccinimide is a five-membered cyclic dicarboximide compound having a bromo substituent on the nitrogen atom. It has a role as a reagent. It is a dicarboximide, a pyrrolidinone and an organobromine compound. It is functionally related to a succinimide.

Preparation

N-Bromosuccinimide is prepared by addition of bromine to a cold aqueous solution of succinimide or by reaction of succinimide with NaBrO2 in the presence of HBr.

1.62mol (160g) succinimide is dissolved in a mixture of 1.60mol (64g) NaOH, 300g crushed ice and 400ml water. Cool the mixture in an ice bath, and add 85ml (1.65 mol, 264g) Br2 at once while stirring violently. Stir for two more minutes, then filter the precipitated product and wash with ice water. Dry in a desiccator. Yield 75-81%.
Don't clean up NBS too much, the stinky yellow stuff still containing a bit of Br2 works best. N-Bromosuccinimide is a brominating agent that replaces hydrogen atoms in benzylic or allylic positions. It is used in the oxidation of secondary alcohols to ketones and in controlled low-energy brominations.

Flammability and Explosibility

Non flammable

Safety Profile

Poison by intraperitoneal route. An irritating poison to skin, eyes, and mucous membranes. Reacts explosively with adme, dtallyl sulfide, and hydrazine hydrate. Explosive reaction with propiononitrile after heating to 105℃ for 24 hours. Violent reaction with dtbenzoyl peroxide + 4-tok acid. When heated to decomposition it emits toxic fumes of Brand NOx. See also BROMIDES and NITROGEN MONOXIDE.

Definition

N-bromosuccinimide is a five-membered cyclic dicarboximide compound having a bromo substituent on the nitrogen atom. It has a role as a reagent and is functionally related to a succinimide. It is a dicarboximide, a pyrrolidinone, and an organobromine compound.

Purification Methods

N-Bromosuccinimide (30g) is purified by dissolving rapidly in 300mL of boiling water and filtering through a fluted filter paper into a flask immersed in an ice bath, and left for 2hours. The crystals are filtered off, washed thoroughly with ca 100mL of ice-cold water and drained on a Büchner funnel before drying under vacuun over P2O5 or CaCl2 [Dauben & McCoy J Am Chem Soc 81 4863 1959]. This brominating agent has also been crystallised from acetic acid or water (10 parts), washed in water and dried in vacuo [Wilcox et al. J Am Chem Soc 108 7693 1986, Shell et al. J Am Chem Soc 108 121 1986, Phillips & Cohen J Am Chem Soc 108 2013 1986, Beilstein 21/9 V 543.]