UN_1099

Allyl bromide

Allyl bromide

Chemical compound

Allyl bromide (3-bromopropene) is an organic halide. It is an alkylating agent used in synthesis of polymers, pharmaceuticals, perfumes[2] 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.[3]

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Preparation

Hydrohalogenation

Allyl bromide is produced commercially from allyl alcohol and hydrobromic acid:[3]

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.[3]

Halogenation

Allyl bromide can be also produced by reacting allyl alcohol and pure bromine.

Br2+ CH2=CHCH2OH → CH2=CHCH2Br + HBr + H2O

Reactions and uses

Electrophilic properties

Allyl bromide is an electrophilic alkylating agent.[4] 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.[3]

Preparation of Grignard reagent

Allyl bromide reacts with magnesium metal in dry ether to form allylmagnesium bromide, a Grignard reagent:[5]

CH2=CHCH2Br + Mg → CH2=CHCH2MgBr

Preparation of Allyl Benzene

Allyl bromide reacts with benzene and a Lewis acid to make Allyl Benzene

C6H6 + CH2=CHCH2Br (FeCl3/AlCl3)→ C₆H₅CH₂CH=CH₂

This reaction is particurarly useful in pharmacy and can be used to make many pharamacueticals such as amphetamines

References

  1. [1]
    CRC handbook of chemistry and physics : a ready-reference book of chemical and physical data. William M. Haynes, David R. Lide, Thomas J. Bruno (2016-2017, 97th ed.). Boca Raton, Florida. 2016. ISBN 978-1-4987-5428-6. OCLC 930681942.{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: others (link)
  2. [2]
    PubChem. "Hazardous Substances Data Bank (HSDB) : 622". pubchem.ncbi.nlm.nih.gov. Retrieved 2022-03-04.
  3. [3]
    Yoffe, David; Frim, Ron; Ukeles, Shmuel D.; Dagani, Michael J.; Barda, Henry J.; Benya, Theodore J.; Sanders, David C. (2013). "Bromine Compounds". Ullmann's Encyclopedia of Industrial Chemistry. pp. 1–31. doi:10.1002/14356007.a04_405.pub2. ISBN 978-3-527-30385-4.
  4. [4]
    Bolton, Roger (2001-04-15), "Allyl Bromide", in John Wiley & Sons, Ltd (ed.), Encyclopedia of Reagents for Organic Synthesis, Chichester, UK: John Wiley & Sons, Ltd, pp. ra045, doi:10.1002/047084289x.ra045, ISBN 978-0-471-93623-7, retrieved 2022-03-04
  5. [5]
    Pierre Mazerolles, Paul Boussaguet, Vincent Huc (1999). "6-Chloro-1-Hexene and 8-Chloro-1-Octene". Organic Syntheses. 76: 221. doi:10.15227/orgsyn.076.0221.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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