1- Chloro-l,3-butadienes

Chloroprene Elastomers. Polychloroprene is a polymer of 2-chloro-l,3-butadiene. The elastomer is largely composed of the trans isomer. There are two basic polymer types the W-type and the G-type. G-types are made by using a sulfur-modified process W-types use no sulfur modification. As a result, G-types possess excellent processing and dynamic properties, and tend to be used in V-belts. However, they have poorer aging properties than W-types. The W-types tend to be used in appHcations requiring better aging, such as roUs and mechanical goods (see Elastomers, SYNTHETIC-POLYCm.OROPRENE). 

Chlorobenzene (monochlorobenzene) Chlorobromomethane 2-Chloro-l, 3-butadiene, see Chloroprene Chlorodifluoromethane (Freon 22)... 

Polychloroprene rubber (CR) is the most popular and versatile of the elastomers used in adhesives. In the early 1920s, Dr. Nieuwland of the University of Notre Dame synthesized divinyl acetylene from acetylene using copper(l) chloride as catalyst. A few years later, Du Pont scientists joined Dr. Nieuwland s research and prepared monovinyl acetylene, from which, by controlled reaction with hydrochloric acid, the chloroprene monomer (2-chloro-l, 3-butadiene) was obtained. Upon polymerization of chloroprene a rubber-like polymer was obtained. In 1932 it was commercialized under the tradename DuPrene which was changed to Neoprene by DuPont de Nemours in 1936. 

A number of different synthetic rubbers are produced commercially by diene polymerization. Both cis- and frrms-polyisoprene can be made, and the synthetic rubber thus produced is similar to the natural material. Chloroprene (2-chloro-l,3-butadiene) is polymerized to yield neoprene, an excellent, although expensive, synthetic rubber with good weather resistance. Neoprene is used in the production of industrial hoses and gloves, among other things. 

Chloroprene (2-chloro-l,3-butadiene 105), which is a mass-produced, inexpensive industrial material, is an excellent precursor to a variety of terminal allenes 107 [97]. The palladium-catalyzed reaction of 105 with pronucleophiles 106 in the presence of an appropriate base gave the terminal allenes 107 in good yields (Scheme 3.53). The palladium species generated from Pd2(dba)3-CHC13 and DPEphos was a good catalyst for these reactions of chloroprene. In contrast, (Z)-l-Phenyl-2-chloro-l,3-buta-diene, which is isostructural with the bromo-substrate 101, was nearly inert under these conditions. There is no substituent at the vicinal ris-position to the chloride in 105, which allows oxidative addition of the C-Cl bond in 105 to the Pd(0) species. 

Cycloadditions to a cyano group are comparatively rare. The high-temperature reactions of 1,3-dienes, e.g. butadiene, isoprene and 2-chloro-l,3-butadiene, with dicyanogen, propionitrile or benzonitrile result in formation of pyridines (equation 80)70. Sulfonyl cyanides 147, obtained by the action of cyanogen chloride on sodium salts of sulfinic acids, add to dienes to give dihydropyridines 148, which are transformed into pyridines 149 by oxidation (equation 81)71. 

Polychloroprene is the polymer of 2-chloro-l,3 butadiene. Emulsion polymerization produces an almost entirely trans-1,4 polymer, which is highly crystalline. Less crystalline polychloroprenes are produced by incorporating several wt.% of 2,3-dichloro-l,3 butadiene into the polymer to break up crystalline sequences. 

Another chlorinated compound which, like vinyl chloride, is used only in its polymeric form, is chloroprene (2-chloro-l,3-butadiene), which is polymerized to make neoprene, first produced in 1940. As far as is known (17) y the monomer is made commercially only from acetylene via addition of hydrochloric acid to monovinylacetylene in the presence of cuprous chloride, but syntheses from butylenes or butadiene have been described. The production of chloroprene exceeded 100,000,000 pounds per year at the wartime peak and has been somewhat lower since then, but in view of the many valuable properties of the neoprene rubber it will continue to be important. 

Chem. Abstr. Serv. Reg. No.. 126-99-8 Chem. Abstr. Name. 2-Chloro-l,3-butadiene Synonyms 2-Chlorobutadiene (3-chloroprene... 

Haley, T.J. (1978) Chloroprene (2-chloro-l,3-butadiene)—what is the evidence for its carcinogenicity Clin. Toxicol., 13, 153-170... 

Melnick, R.L., Elwell, M.R., Roycroft, J.H., Chou, B.J., Ragan, H.A. Miller, R.A. (1996) Toxicity of inhaled chloroprene (2-chloro-l,3-butadiene) in F344 rats and B6C3Fi mice. Toxicology, 108, 79-91... 

Westphal, G.A., Blaszkewicz, M., Leutbecher, M., Muller, A., Hallier, E. Bolt, H.M. (1994) Bacterial mutagenicity of 2-chloro-l,3-butadiene (chloroprene) caused by decomposition products. Arch. Toxicol., 68, 79-84... 

Chloro-l,3-butadiene (chloroprene) is the monomer from which the elastomer neoprene is prepared. 2-Chloro-l,3-butadiene is the thermodynamically controlled product formed by addition of hydrogen chloride to vinylacetylene (H2C=CHC=CH). The principal product under conditions of kinetic control is the allenic chloride 4-chloro-1,2-butadiene. Suggest a mechanism to account for the formation of each product. 

The molecular formula of the product, C10H9ClO2, is that of a 1 1 Diels-Alder adduct between 2-chloro-l,3-butadiene and benzoquinone. 

Chloroprene (boiling point 59.4°C, density 0.9583) is, chemically, a chlorovinyl ester of hydrochloric acid and can be manufactured by polymerizing acetylene to vinyl acetylene using a weak solution containing ammonium chloride (NH4C1), cuprous chloride (Cu2Cl2), and potassium chloride (KC1) as catalyst. The off-gas from the reactor has its water condensed out and is then fractionated. Aqueous hydrochloric acid at 35 to 45 °C is then reacted with the vinyl acetylene in the presence of cupric chloride to give chloroprene (2-chloro-l,3-butadiene). 

Hazard of rapid polymerization initiated by internally formed peroxides List A. Normal liquids Discard or test for peroxides after 6 months1 Chloroprene (2-chloro-l,3-butadiene) Vinyl acetate... 

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