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Chloroprene
Chloroprene
Chloroprene
Chloroprene
Chloroprene
Names
Preferred IUPAC name
2-Chlorobuta-1,3-diene
Other names
  • Chloroprene
  • 2-chloro-1,3-butadiene
  • Chlorobutadiene
  • β-Chloroprene
Identifiers
3D model (JSmol)
741875
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.004.381 Edit this at Wikidata
EC Number
  • 204-818-0
277888
KEGG
RTECS number
  • EL9625000
UNII
UN number 1991
  • InChI=1S/C4H5Cl/c1-3-4(2)5/h3H,1-2H2 checkY
    Key: YACLQRRMGMJLJV-UHFFFAOYSA-N checkY
  • InChI=1/C4H5Cl/c1-3-4(2)5/h3H,1-2H2
    Key: YACLQRRMGMJLJV-UHFFFAOYAQ
  • C=C(Cl)C=C
Properties
C4H5Cl
Molar mass 88.53 g·mol−1
Appearance Colorless liquid
Odor Pungent, ether-like
Density 0.9598 g/cm3
Melting point −130 °C (−202 °F; 143 K)[1]
Boiling point 59.4 °C (138.9 °F; 332.5 K)[1]
0.026 g/100 mL
Solubility in diethyl ether miscible[1]
Solubility in acetone miscible[1]
Solubility in benzene miscible[1]
Solubility in ethanol soluble
Vapor pressure
  • 118 mmHg (10 °C (50 °F; 283 K))
  • 188 mmHg (20 °C (68 °F; 293 K))
  • 215 mmHg (25 °C (77 °F; 298 K))[1]
1.4583
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Highly flammable, irritant, toxic
GHS labelling:[1]
GHS02: FlammableGHS07: Exclamation markGHS08: Health hazard
Danger
H225, H302, H315, H319, H332, H335, H350, H373
P203, P210, P233, P240, P241, P242, P243, P260, P261, P264, P264+P265, P270, P271, P280, P281, P301+P317, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P308+P313, P317, P318, P319, P321, P330, P332+P317, P337+P313, P362+P364, P370+P378, P403+P233, P403+P235, P405, P501
NFPA 704 (fire diamond)
[3]
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 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. gasolineInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
2
3
1
Flash point −4 °C (25 °F; 269 K)[1]
Explosive limits 1.9%–20.0%[1]
10 ppm (skin)[1] (TWA)
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]
NIOSH (US health exposure limits):[4]
PEL (Permissible)
 25 ppm (90 mg/m3, TWA, skin)
REL (Recommended)
 1 ppm (3.6 mg/m3, Ca C, [15-minute])
IDLH (Immediate danger)
 300 ppm (1086 mg/m3)
Related compounds
Related Dienes
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Chloroprene (IUPAC name 2-chlorobuta-1,3-diene) is a chemical compound with the molecular formula CH2=CCl−CH=CH2.[5] Chloroprene is a colorless volatile liquid, almost exclusively used as a monomer for the production of the polymer polychloroprene, better known as neoprene, a type of synthetic rubber.

History

[edit]

Although it may have been discovered earlier, chloroprene was largely developed by DuPont during the early 1930s, specifically with the formation of neoprene in mind.[6] The chemists Elmer K. Bolton, Wallace Carothers, Arnold Collins and Ira Williams are generally accredited with its development and commercialisation although the work was based upon that of Julius Arthur Nieuwland, with whom they collaborated.[7]

Production

[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:[5]

CH2=CHCH=CH2 + Cl2 → ClCH2CH=CHCH2Cl
ClCH2CH=CHCH2Cl → ClCH2CHClCH=CH2
ClCH2CHClCH=CH2 → CH2=CClCH=CH2 + HCl

The chief impurity in chloroprene prepared in this way is 1-chlorobuta-1,3-diene, which is usually separated by distillation.[5] In 1983, approximately 2 million kilograms (2,200 short tons) were produced in this manner.

Acetylene process

[edit]

Until the 1960s, chloroprene production was dominated by the "acetylene process," which was modeled after the original synthesis of vinylacetylene.[6] 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:[5]

The acetylene process is energy-intensive and has high investment costs. Furthermore, the intermediate vinyl acetylene is unstable. This "acetylene process" has been replaced by the chlorination of 1,3-butadiene.

Hazards

[edit]

Chloroprene may explosively polymerize. The peroxide catalyzes this.[8]

Occupational exposure limits

[edit]

A table of occupational exposure limits (OELs) from various jurisdictions follows. In general, the OELs range from 0.55 to 25 ppm.[9]

Occupational exposure limits for chloroprene[citation needed]
Organization Concentration
NIOSH REL 1 ppm
ACGIH TLV 8-hour TWA 10 ppm
OSHA PEL 8-hour TWA 25 ppm
Mine Safety and Health Administration 25 ppm
Austria OEL MAK-TMW 5 ppm
Belgium OEL TWA 10 ppm
Denmark OEL ceiling concentration 1 ppm
Finland OEL TWA 1 ppm
France OEL VME 10 ppm
Hungary OEL TWA 5 ppm
Iceland OEL Short Term Exposure Limit (STEL) 1 ppm
Korea OEL TWA 10 ppm
Mexico OEL TWA 10 ppm
New Zealand OEL TWA 10 ppm
Norway OEL TWA 1 ppm
Peru OEL TWA 10 ppm
Poland OEL MAC TWA 0.55 ppm
Sweden OEL TWA 1 ppm
Switzerland OEL MAK-week 5 ppm
The Netherlands OEL MAC-TGG 5 ppm

Environment

[edit]

The fate of chloroprene in the environment has been examined.[10] Due to its volatility and extreme reactivity, it is not expected to bioaccumulate.[11]

Health

[edit]

Chloroprene is toxic. Chloroprene is potentially carcinogenic, can cause temporary hair loss on the exposed area, and can cause damage to the eyes and skin.[12]

The Environmental Protection Agency designated chloroprene as likely to be carcinogenic to humans based on evidence from studies that showed a statistically significant association between occupational chloroprene exposure and the risk of lung cancer.[11] There are criticisms of this report that indicate that the unsafe exposure levels may have been exaggerated badly based on levels for known carcinogens.[13]

Chronic exposure to chloroprene may have the following symptoms: liver function abnormalities, disorders of the cardiovascular system, and depression of the immune system.[1]

One fatality as a result of chloroprene intoxication has been recorded, which was a result of cleaning a container used for chloroprene.[14]

References

[edit]
  1. ^ a b c d e f g h i j k "Chloroprene - Laboratory Chemical Safety Summary (LCSS)". pubchem.ncbi.nlm.nih.gov. National Library of Medicine. Retrieved 25 December 2025.
  2. ^ a b "ß-Chloroprene". Immediately Dangerous to Life or Health Concentrations. National Institute for Occupational Safety and Health.
  3. ^ "Chloroprene, Stabilized | Cameo Chemicals | NOAA". cameochemicals.noaa.gov. Retrieved 2018-12-14.
  4. ^ "NIOSH Pocket Guide to Chemical Hazards".
  5. ^ a b c d Rossberg, M.; Lendle, W.; Pfleiderer, G.; Tögel, A.; Dreher, E.-L.; Langer, E.; Rassaerts, H.; Kleinschmidt, P.; Strack, H.; Cook, R.; Beck, U.; Lipper, K.-A.; Torkelson, T. R.; Löser, E.; Beutel, K.K.; Mann, T. (15 July 2006). "Chlorinated Hydrocarbons". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a06_233.pub2. ISBN 978-3-527-30673-2.
  6. ^ a b Carothers, Wallace H.; Williams, Ira.; Collins, Arnold M.; Kirby, James E. (November 1931). "Acetylene Polymers and their Derivatives. II. A New Synthetic Rubber: Chloroprene and its Polymers". Journal of the American Chemical Society. 53 (11): 4203–4225. doi:10.1021/ja01362a042.
  7. ^ Smith, John K. (January 1985). "The Ten-Year Invention: Neoprene and Du Pont Research, 1930-1939". Technology and Culture. 26 (1): 34–55. doi:10.2307/3104528. JSTOR 3104528. S2CID 113234844.
  8. ^ "Chloroprene, Stabilized | CAMEO Chemicals". cameochemicals.noaa.gov. NOAA. Retrieved 25 December 2025.
  9. ^ "Template Package 4". Centers for Disease Control and Prevention. Retrieved 2018-11-24.
  10. ^ National Institute of Environmental Health Sciences. National Toxicology Program (2016). Report on Carcinogens, fourteenth edition. ISBN 978-1-5231-0852-7. OCLC 990561140.
  11. ^ a b "4.7 - Evaluation of Carcinogenicity". Toxicological Review of Chloroprene - In Support of Summary Information on the Integrated Risk Information System (IRIS) (Report). Washington, DC: U.S. Environmental Protection Agency. 2010. p. 96. EPA/635/R-09/010F.
  12. ^ "Hazardous Substance Fact Sheet" (PDF). New Jersey Department of Health and Senior Services.
  13. ^ "The IRIS Review Process: Chloroprene and the Criticality of Good Science" (PDF). House Committee on Science, Space, and Technology Republicans. S2CID 33811055.
  14. ^ Rickert, Annette; Hartung, Benno; Kardel, Bernd; Teloh, Johanna; Daldrup, Thomas (2012-02-10). "A fatal intoxication by chloroprene". Forensic Science International. 215 (1–3): 110–113. doi:10.1016/j.forsciint.2011.03.029. ISSN 0379-0738. PMID 21511420.
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