Crotyl chloride

Crotyl chloride is an organochloride with the molecular formula C₄H₇Cl or H₃C(CH)₂CH₂Cl.^[1] It is a derivative of 2-butene with a chlorine atom at a terminal carbon. It exhibits cis-trans isomerism about the double bond; the (E) isomer predominates in commercial preparations.^[2]

Crotyl chloride

Names
Preferred IUPAC name (2E)-1-Chlorobut-2-ene
Other names 1-Chloro-2-butene, 1-chlorobut-2-ene, 2-butenyl chloride, gamma-methylallyl chloride
Identifiers
CAS Number	591-97-9 Y
3D model (JSmol)	Interactive image
Beilstein Reference	605304
ChemSpider	553496
ECHA InfoCard	100.008.855
PubChem CID	637923
RTECS number	EM4264000
UNII	G6Y5C34N83 Y
CompTox Dashboard (EPA)	DTXSID5052258
InChI InChI=1S/C4H7Cl/c1-2-3-4-5/h2-3H,4H2,1H3/b3-2+ Key: YTKRILODNOEEPX-NSCUHMNNSA-N InChI=1/C4H7Cl/c1-2-3-4-5/h2-3H,4H2,1H3/b3-2+ Key: YTKRILODNOEEPX-NSCUHMNNBH
SMILES C/C=C/CCl
Properties
Chemical formula	C4H7Cl
Molar mass	90.55 g·mol−1
Appearance	Liquid
Density	0.949 g/cm3
Melting point	−65 °C (−85 °F; 208 K)
Boiling point	84 °C (183 °F; 357 K)
Vapor pressure	37084 mmHG
Hazards
NFPA 704 (fire diamond)	2 3 2
Flash point	−15 °C (5 °F; 258 K)
Autoignition temperature	510 °C (950 °F; 783 K)
Related compounds
Related chloroalkenes	Allyl chloride Methallyl chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Preparation

It can be produced by the chlorination of crotyl alcohol by chlorinating agents such as triphenylphosphine dichloride.^[2]

Applications

Treatment of crotyl halides with magnesium produces crotyl Grignard reagents. The chloride is more stable than the bromide.^[3] These reagents can then be used in the Grignard reaction for crotylation of carbonyl compounds.^[4]

Dehydrohalogenation of crotyl chloride was once used as a laboratory route to produce butadiene, though the pyrolysis of cyclohexene is preferred according to Organic Syntheses.^[5] Crotyl chloride may be used as a model compound for other allylic hydrochlorocarbons.^[6]