Allyl bromide

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]

Allyl bromide

Skeletal formula
Ball-and-stick model
Names
Preferred IUPAC name 3-Bromoprop-1-ene
Other names Allyl bromide 3-Bromopropene 3-Bromopropylene 3-Bromo-1-propene Bromoallylene 2-Propenyl bromide
Identifiers
CAS Number	106-95-6 Y
3D model (JSmol)	Interactive image Interactive image
ChemSpider	7553 Y
ECHA InfoCard	100.003.134
EC Number	203-446-6
PubChem CID	7841
RTECS number	UC7090000
UNII	FXQ8X2F74Z Y
UN number	1099
CompTox Dashboard (EPA)	DTXSID8024442
InChI InChI=1S/C3H5Br/c1-2-3-4/h2H,1,3H2 Y Key: BHELZAPQIKSEDF-UHFFFAOYSA-N Y InChI=1/C3H5Br/c1-2-3-4/h2H,1,3H2 Key: BHELZAPQIKSEDF-UHFFFAOYAI
SMILES BrCC=C C=CCBr
Properties
Chemical formula	C3H5Br
Molar mass	120.977 g·mol−1
Appearance	Clear to light yellow liquid
Odor	Unpleasant, irritating, pungent
Density	1.398 g/cm3
Melting point	−119 °C (−182 °F; 154 K)
Boiling point	71 °C (160 °F; 344 K)
Solubility in water	0.38 g/100 g H2O [1]
log P	1.79[1]
Vapor pressure	18.6 kPa
Magnetic susceptibility (χ)	−58.6·10−6 cm3·mol−1[1]
Refractive index (nD)	1.4697 (20 °C, 589.2 nm)
Viscosity	0.471 cP[1]
Dipole moment	≈1.9 D[1]
Thermochemistry
Std enthalpy of formation (ΔfH⦵298)	12.2 kJ·mol−1 (liquid) 45.2 kJ·mol−1 (gas)[1]
Enthalpy of vaporization (ΔfHvap)	32.73 kJ·mol−1[1]
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H225, H301, H314, H330, H331, H340, H350, H400
Precautionary statements	P201, P202, P210, P233, P240, P241, P242, P243, P260, P261, P264, P270, P271, P273, P280, P281, P284, P301+P310, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P308+P313, P310, P311, P320, P321, P330, P363, P370+P378, P391, P403+P233, P403+P235, P405, P501
NFPA 704 (fire diamond)	3 3 1
Flash point	−2 to −1 °C
Autoignition temperature	280 °C (536 °F; 553 K)
Explosive limits	4.3–7.3 %
Threshold limit value (TLV)	0.1 ppm[1] (TWA), 0.2 ppm[1] (STEL)
Safety data sheet (SDS)	MSDS at Oxford University
Related compounds
Related compounds	Allyl chloride Allyl iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

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]

Reactions and uses

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]

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

CH₂=CHCH₂Br + Mg → CH₂=CHCH₂MgBr