2-Chloro-1.3-butadiene, polymerization

Moreover, the operation can also be accelerated by employing a catalyst (cuprous chloride) in solution in an organic solvent (such as a-picoline), and by raising the temperature. Above 160 0, however, large amounts of by-products are formed 1-chloro butadiene, hydrochloric acid and especially polymers. Thus, to prevent these side reactions it is preferable to maintain a low thermal level, 105 to 125°C, and distill under partial vacuum (about 20 kPa absolute), in the presence of an inhibitor intended to prevent polymerizations from developing (phenothiazine). For a once-through conversion of 1,4-dichloro 2-butenes of about 80 per cent, molar selectivity of the 3,4-isomer exceeds 75 per cen t. 

As the demand for rubber increased so did the chemical industry s efforts to prepare a synthetic sub stitute One of the first elastomers (a synthetic poly mer that possesses elasticity) to find a commercial niche was neoprene discovered by chemists at Du Pont in 1931 Neoprene is produced by free radical polymerization of 2 chloro 1 3 butadiene and has the greatest variety of applications of any elastomer Some uses include electrical insulation conveyer belts hoses and weather balloons... 

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. 

Chemistry of polychloroprene rubber. Polychloroprene elastomers are produced by free-radical emulsion polymerization of the 2-chloro-1,3-butadiene monomer. The monomer is prepared by either addition of hydrogen chloride to monovinyl acetylene or by the vapour phase chlorination of butadiene at 290-300°C. This latter process was developed in 1960 and produces a mixture of 3,4-dichlorobut-l-ene and 1,4-dichlorobut-2-ene, which has to be dehydrochlorinated with alkali to produce chloroprene. 

Chloroprene (2-chloro 1,3-butadiene), a conjugated non-hydrocarbon diolefm, is a liquid that boils at 59.2°C and while only slightly soluble in water it is soluble in alcohol. The main use of chloroprene is to polymerize it to neoprene rubber. 

Polychloroprene is the oldest synthetic rubber. It is produced by the polymerization of 2-chloro-1,3-butadiene in a water emulsion with potassium sulfate as a catalyst ... 

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. 

The presence of halogen atoms appears to exert little, if any, effect on catalyst activity, but it can influence the course of the metathesis reaction. Vinylic halides are unreactive, as exemplified by the ring-opening polymerization of l-chloro-l,5-cyclooctadiene, which afforded a perfectly alternating copolymer of butadiene and chloroprene (7/2) via polymerization exclusively through the unsubstituted double bond. 

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. 

Draw structures for the different ways in which a monomer unit could be added to a growing chain in a radical-chain polymerization of 2-chloro-1,3-butadiene. 

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... 

At about the same time, Wallace Carothers and his colleagues discovered a chlorine derivative of butadiene that polymerized to give a rubbery polymer that DuPont eventually marketed as Neoprene. Note the similarity in the structures of isoprene and 2-chloro-1,3-butadiene (chloroprene) ... 

Other synthetic rubbers can be prepared by the polymerization of different 1,3-dienes usingZiegler-Natta catalysts. For example, the polymerization of 1,3-butadiene affords fZ -poly(l,3-butadiene), and the polymerization of 2-chloro-1,3-butadiene yields neoprene, a polymer used in wet suits and tires. 

Similar to the case of the polymers with saturated carbon chain backbone, different substitutions are possible to the backbone of the unsaturated macromolecules. One common substitution is with halogens. Chloroprene (also known as neoprene) is formed from the polymerization of 2-chloro-1,3-butadiene and probably is the most widely used polymer from this class. It has rubber-like properties and is known for its better oil... 

The 2-pentenenitrile, 2-methyl-3-butenenitrile, and methylglutaronitrile in Figure 1.1 are by-products of this reaction sequence. duPont is still studying the phosphines used as ligands for the nickel in an effort to find one bulky enough to favor terminal addition only.214 Reduction of the various nitriles leads to the amines in Figure 1.1, including the cyclic ones. The 2,3-dichloro-l,3-buta-diene is probably a by-product in the synthesis of 2-chloro-1,3-butadiene used to make Neoprene rubber. duPont also polymerizes acrylonitrile to prepare poly (acrylonitrile) fiber (Orion). Acetonitrile is obtained as a by-product of the ammoxidation of propylene to produce acrylonitrile (reaction 1.20). 

Neoprene. Duprene GR-M polychloroprene poly(2 -chloro-1,3 -butadiene). Mol wt range of 100.000-300.000. An oil-resistant synthetic rubber, with predominantly Irans configuration made by polymerization of chlo-roprene. Prepn W. H. Carol hers er al, J. Am. Chem. Soc 53, 4203 (1931). Review P. J. Johnson in Ktrk-Othmer Encyclopedia of Chemical Technology vol. 8 (Wiley-Interscience, New York, 3rd ed., 1979) pp 515-534. 

Neoprene is a synthetic rubber made by polymerizing 2-chloro-l,3-butadiene in the presence of a Ziegler-Natta catalyst that causes all the double bonds in the polymer to have the trans configuration. Neoprene is used to make wet suits, shoe soles, tires, hoses, and coated fabrics. 

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