Allyl bromide
Allyl bromide (3-bromopropene) is an organic halide. It is an alkylating agent used in synthesis of polymers, pharmaceuticals, perfumes[1] and other organic compounds. Allyl bromide is a colorless liquid, although commercial samples appear yellow or brown. It is an irritant and a potentially dangerous alkylating agent. Allyl bromide is more reactive but more expensive than allyl chloride, and these considerations guide its use.[2]
Preparation
Hydrohalogenation
Allyl bromide is produced commercially from allyl alcohol and hydrobromic acid:[2]
- CH2=CHCH2OH + HBr → CH2=CHCH2Br + H2O
It can also be prepared by the halogen-exchange reaction between allyl chloride and hydrobromic acid or by the allylic bromination of propene.[2]
Reactions and uses
Allyl bromide is an electrophilic alkylating agent.[3] It reacts with nucleophiles, such as amines, carbanions, alkoxides, etc., to introduce the allyl group:
- CH2=CHCH2Br + Nu− → CH2=CHCH2Nu + Br− (Nu− is a nucleophile)
It is used in the synthesis of compounds containing the allyl functionality, such as the pharmaceuticals methohexital, secobarbital and thiamylal.[2]
Allyl bromide reacts with magnesium metal in dry ether to form allylmagnesium bromide, a Grignard reagent:[4]
- CH2=CHCH2Br + Mg → CH2=CHCH2MgBr
References
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