Chloroprene 1748827 224568707 2008-07-09T13:31:36Z Puppy8800 5404759 iw {{Chembox new | Name = Chloroprene | ImageFileL1 = Chloroprene-2D-skeletal.png | ImageSizeL1 = 120px | ImageNameL1 = Chloroprene | ImageFileR1 = Chloroprene-3D-vdW.png | ImageSizeR1 = 120px | ImageNameR1 = Chloroprene | IUPACName = 2-Chloro-1,3-butadiene | OtherNames = Chloroprene | Section1 = {{Chembox Identifiers | SMILES = C=C(Cl)C=C | CASNo = 126-99-8 | RTECS = EL9625000 }} | Section2 = {{Chembox Properties | Formula = C<sub>4</sub>H<sub>5</sub>Cl | MolarMass = 88.5365 g/mol | Appearance = Colorless liquid. | Density = 0.9598 g/cm<sup>3</sup>, liquid. | Solubility = 0.026 g/100 mL, liquid. | MeltingPtC = -130 | BoilingPtC = 59.4 | Viscosity = }} | Section3 = {{Chembox Structure | MolShape = | Dipole = }} | Section7 = {{Chembox Hazards | ExternalMSDS = | MainHazards = Highly flammable, toxic. | NFPA-H = 2 | NFPA-F = 3 | NFPA-R = | FlashPt = -15.6°C | RPhrases = {{R45}}, {{R11}}, {{R20/22}},<br />{{R36/37/38}}, {{R48/20}} | SPhrases = {{S53}}, {{S45}} }} | Section8 = {{Chembox Related | Function = [[Diene]]s | OtherFunctn = [[Butadiene]]<br />[[Isoprene]] | OtherCpds = [[Vinyl chloride]] }} }} '''Chloroprene''' is the common name for the [[organic compound]] '''2-chloro-1,3-butadiene''', which has the [[chemical formula]] CH<sub>2</sub>=CCl-CH=CH<sub>2</sub>. 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 [[DuPont]] gave it when the company first developed it and currently used by DuPont Performance Elastomers. ==Production of chloroprene== Chloroprene is produced in three steps from [[Butadiene|1,3-butadiene]]: (i) [[chlorination]], (ii) isomerization of part of the product stream, and (iii) [[Dehydrohalogenation|dehydrochlorination]] of 3,4-dichloro-1-butene. [[Chlorine]] adds to 1,3-butadiene to afford a mixture of 3,4-dichloro-1-butene and 2,3-dichloro-2-butene. The 2,3-chloro isomer is subsequently isomerized to 3,4 isomer, which in turn is treated with base to induce dehydrochlorination to 2-chloro-1,3-butadiene. 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 were produced in this manner.<ref name=Ross>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</ref> The chief impurity in chloroprene prepared in this way is 1-chloro-1,3-butadiene, which is usually separated by [[distillation]]. ===Acetylene process=== Until the 1960s, chloroprene production was dominated by the “acetylene process,” which was modeled after the original synthesis of [[vinyl acetylene]].<ref>{{cite journal | author = [[Wallace H. Carothers]], Ira Williams, Arnold M. Collins, and James E. Kirby | title = Acetylene Polymers and their Derivatives. II. A New Synthetic Rubber: Chloroprene and its Polymers | journal = [[J. Am. Chem. Soc.]]| year = 1937 | volume = 53 | pages = 4203–4225 | doi = 10.1021/ja01362a042}}</ref> In this process, [[acetylene]] is dimerized to give vinyl acetylene, which is then combine with [[hydrogen chloride]] to afford in succession vinyl acetylene, 3-chloro-1,2-butadiene, which, finally in the presence of [[cuprous chloride]], rearranges to the targeted 2-chloro-1,3-butadiene.<ref name=Ross/> The conversion is shown here: [[Image:Chloroprene synthesis.png|400px]] This process had disadvantages in that it is very energy-intensive and has high investment costs. Furthermore, the intermediate vinyl acetylene is unstable. ==References== <references/> *[http://www.iisrp.com/WebPolymers/04FinalPolychloropreneIISRP.pdf Polychloroprene (CR), chloroprene rubber] ==External links== *{{ICSC|0133|01}} *{{PGCH|0133}} *{{ecb}} *[[IARC]] Monograph "[http://www-cie.iarc.fr/htdocs/monographs/vol71/003-chloroprene.html Chloroprene.]" [[Category:Dienes]] [[Category:Monomers]] [[Category:Organochlorides]] [[Category:Hazardous air pollutants]] [[Category:IARC Group 2B carcinogens]] [[ar:كلوروبرين]] [[cs:Chloropren]] [[de:Chloropren]] [[es:Cloropreno]] [[nl:Chloropreen]] [[ja:クロロプレン]] [[pl:Chloropren]] [[ru:Хлоропрен]] [[sk:Chloroprén]] [[vi:Cloropren]] [[zh:氯丁二烯]]