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IUPAC name
Other names
Chloroprene, 2-chloro-1,3-butadiene, Chlorobutadiene, β-Chloroprene
3D model (JSmol)
ECHA InfoCard 100.004.381
RTECS number EL9625000
Molar mass 88.5365 g/mol
Appearance Colorless liquid
Odor pungent, ether-like
Density 0.9598 g/cm3
Melting point −130 °C (−202 °F; 143 K)
Boiling point 59.4 °C (138.9 °F; 332.5 K)
0.026 g/100 mL
Solubility soluble in alcohol, diethyl ether
miscible in ethyl ether, acetone, benzene
Vapor pressure 188 mmHg (20 °C)[1]
Main hazards Highly flammable, toxic.
R-phrases (outdated) R45, R11, R20/22,
R36/37/38, R48/20
S-phrases (outdated) S53, S45
NFPA 704
Flammability code 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g., gasolineHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
Flash point −15.6 °C (3.9 °F; 257.5 K)
Explosive limits 1.9%–11.3%[1]
Lethal dose or concentration (LD, LC):
450 mg/kg (rat, oral)
3207 ppm (rat, 4 hr)[2]
1052 ppm (rabbit, 8 hr)
350 ppm (cat, 8 hr)[2]
US health exposure limits (NIOSH):
PEL (Permissible)
TWA 25 ppm (90 mg/m3) [skin][1]
REL (Recommended)
Ca C 1 ppm (3.6 mg/m3) [15-minute][1]
IDLH (Immediate danger)
300 ppm[1]
Related compounds
Related Dienes
Related compounds
Vinyl chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Chloroprene is the common name for the organic compound 2-chlorobuta-1,3-diene, which has the formula CH2=CCl−CH=CH2. This colorless liquid is the monomer for the production of the polymer polychloroprene, a type of synthetic rubber. Polychloroprene is better known to the public as Neoprene, the trade name given by DuPont.

Production of chloroprene[edit]

Chloroprene is produced in three steps from 1,3-butadiene: (i) chlorination, (ii) isomerization of part of the product stream, and (iii) dehydrochlorination of 3,4-dichlorobut-1-ene.

Chlorine adds to 1,3-butadiene to afford a mixture of 3,4-dichlorobut-1-ene and 1,4-dichlorobut-2-ene. The 1,4-dichloro isomer is subsequently isomerized to 3,4 isomer, which in turn is treated with base to induce dehydrochlorination to 2-chlorobuta-1,3-diene. This dehydrohalogenation entails loss of a hydrogen atom in the 3 position and the chlorine atom in the 4 position thereby forming a double bond between carbons 3 and 4. In 1983, approximately 2,000,000 kg was produced in this manner.[3] The chief impurity in chloroprene prepared in this way is 1-chlorobuta-1,3-diene, which is usually separated by distillation.

Acetylene process[edit]

Until the 1960s, chloroprene production was dominated by the "acetylene process," which was modeled after the original synthesis of vinylacetylene.[4] In this process, acetylene is dimerized to give vinyl acetylene, which is then combined with hydrogen chloride to afford 4-chloro-1,2-butadiene (an allene derivative), which in the presence of copper(I) chloride, rearranges to the targeted 2-chlorobuta-1,3-diene:[3] Chloroprene synthesis.svg

This process is very energy-intensive and has high investment costs. Furthermore, the intermediate vinyl acetylene is unstable.

This "acetylene process" has been replaced by a process which adds Cl2 to one of the double bonds in 1,3-butadiene instead, and subsequent elimination produces HCl instead, as well as chloroprene.

Transportation regulations[edit]

Transportation of uninhibited chloroprene has been banned in the United States by the US Department of Transportation. Stabilized chloroprene is in hazard class 3 (flammable liquid). Its UN number is 1991 and is in packing group 1.


  1. ^ a b c d e "NIOSH Pocket Guide to Chemical Hazards #0133". National Institute for Occupational Safety and Health (NIOSH).
  2. ^ a b "ß-Chloroprene". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  3. ^ a b Manfred Rossberg, Wilhelm Lendle, Gerhard Pfleiderer, Adolf Tögel, Eberhard-Ludwig Dreher, Ernst Langer, Heinz Rassaerts, Peter Kleinschmidt, Heinz Strack, Richard Cook, Uwe Beck, Karl-August Lipper, Theodore R. Torkelson, Eckhard Löser, Klaus K. Beutel, "Chlorinated Hydrocarbons" in Ullmann’s Encyclopedia of Industrial Chemistry, 2006 John Wiley-VCH: Weinheim. doi:10.1002/14356007.a06_233.pub2
  4. ^ Wallace H. Carothers, Ira Williams, Arnold M. Collins, and James E. Kirby (1937). "Acetylene Polymers and their Derivatives. II. A New Synthetic Rubber: Chloroprene and its Polymers". J. Am. Chem. Soc. 53 (11): 4203–4225. doi:10.1021/ja01362a042.

External links[edit]