Allyl bromide (3-bromopropene) is an

organic halide Halocarbon compounds are Chemical compound, chemical compounds in which one or more carbon atoms are linked by covalent bonds with one or more halogen atoms (fluorine, chlorine, bromine or iodine – ) resulting in the formation of organofluor ...

. It is an

alkylating agent Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting ...

used in synthesis of polymers, pharmaceuticals, perfumes 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

. Allyl bromide is more reactive but more expensive than

allyl chloride Allyl chloride is the organic compound with the formula C H2=CHCH2 Cl. This colorless liquid is insoluble in water but soluble in common organic solvents. It is mainly converted to epichlorohydrin, used in the production of plastics. It is a c ...

, and these considerations guide its use.

Preparation

Hydrohalogenation

Allyl bromide is produced commercially from

allyl alcohol Allyl alcohol (IUPAC name: prop-2-en-1-ol) is an organic compound with the structural formula . Like many alcohols, it is a water-soluble, colourless liquid. It is more toxic than typical small alcohols. Allyl alcohol is used as a precursor to ...

and

hydrobromic acid Hydrobromic acid is an aqueous solution of hydrogen bromide. It is a strong acid formed by dissolving the diatomic molecule hydrogen bromide (HBr) in water. "Constant boiling" hydrobromic acid is an aqueous solution that distills at and contains ...

: :CH₂=CHCH₂OH + HBr → CH₂=CHCH₂Br + H₂O It can also be prepared by the halogen-exchange reaction between

and hydrobromic acid or by the allylic bromination of

propene Propylene, also known as propene, is an unsaturated organic compound with the chemical formula . It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colorless gas with a faint petroleum-like od ...

Reactions and uses

Allyl bromide is an electrophilic alkylating agent. It reacts with

nucleophiles In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...

, such as

amines In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...

, carbanions,

alkoxides In chemistry, an alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They are written as , where R is the organyl substituent. Alkoxides are strong bases and, when ...

, etc., to introduce the

allyl group In organic chemistry, an allyl group is a substituent with the structural formula . It consists of a methylene bridge () attached to a vinyl group (). The name is derived from the scientific name for garlic, . In 1844, Theodor Wertheim isolated ...

: :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 Methohexital or methohexitone (marketed under the brand names Brevital and Brietal) is a drug which is a barbiturate derivative. It is classified as short-acting, and has a rapid onset of action. It is similar in its effects to sodium thiopental ...

secobarbital Secobarbital, sold under the brand name Seconal among others, is a short-acting barbiturate drug originally used for the treatment of insomnia. It was patented by Eli Lilly and Company in 1934 in the United States. It possesses anesthetic, antic ...

and

thiamylal Thiamylal (Surital) is a barbiturate derivative invented in the 1950s. It has sedative, anticonvulsant, and hypnotic effects, and is used as a strong but short acting sedative. Thiamylal is still in current use, primarily for induction in surgica ...

. Allyl bromide reacts with magnesium metal in dry

ether In organic chemistry, ethers are a class of compounds that contain an ether group, a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group (e.g., alkyl or aryl). They have the general formula , where R and R� ...

to form

allylmagnesium bromide Allylmagnesium bromide is a Grignard reagent used for introducing the allyl group. It is commonly available as a solution in diethyl ether. It may be synthesized by treatment of magnesium with allyl bromide while maintaining the reaction temperatur ...

, a Grignard reagent: :CH₂=CHCH₂Br + Mg → CH₂=CHCH₂MgBr :

References

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External links

Entry at chemicalland21.com
Bromoalkenes Allyl compounds