2- Chlorobutadiene

Pyrolysis. Pyrolysis of 1,2-dichloroethane in the temperature range of 340—515°C gives vinyl chloride, hydrogen chloride, and traces of acetylene (1,18) and 2-chlorobutadiene. Reaction rate is accelerated by chlorine (19), bromine, bromotrichloromethane, carbon tetrachloride (20), and other free-radical generators. Catalytic dehydrochlorination of 1,2-dichloroethane on activated alumina (3), metal carbonate, and sulfate salts (5) has been reported, and lasers have been used to initiate the cracking reaction, although not at a low enough temperature to show economic benefits. 

Emulsion polymerization is the most important process for production of elastic polymers based on butadiene. Copolymers of butadiene with styrene and acrylonitrile have attained particular significance. Polymerized 2-chlorobutadiene is known as chloroprene rubber. Emulsion polymerization provides the advantage of running a low viscosity during the entire time of polymerization. Hence the temperature can easily be controlled. The polymerizate is formed as a latex similar to natural rubber latex. In this way the production of mixed lattices is relieved. The temperature of polymerization is usually 50°C. Low-temperature polymerization is carried out by the help of redox systems at a temperature of 5°C. This kind of polymerization leads to a higher amount of desired trans-1,4 structures instead of cis-1,4 structures. Chloroprene rubber from poly-2-chlorbutadiene is equally formed by emulsion polymerization. Chloroprene polymerizes considerably more rapidly than butadiene and isoprene. Especially in low-temperature polymerization emulsifiers must show good solubility and... 

COCH3 >—CN >—COOR >—Cl >—CH2Y >—OCOCH3 >—OR. The effect of a second 1-substituent is roughly additive. 2-Chlorobutadiene and 2,3-dichlorobutadiene [not included in Table XX] are the most reactive monomers examined. A methyl group usually increases reactivity (methyl methacrylate >methyl acrylate, methacrylonitrile > acrylonitrile, methal-lyl>allyl derivatives) and two chlorine atoms are nearly as effective as a carbalkoxy group. 

This explains why 2 methyl butadiene reacts with maleic anhydride (the dienophile) at 30°C in the medium of dioxane with twice the speed as compared with butadiene. But under the same conditions butadiene reacts 10 times faster as compared with 2-chlorobutadiene which has an electron withdrawing group. Thermodynamically unstable compounds are the most reactive dienes. 

List C contains peroxidisable monomers, where the presence of peroxide may initiate exothermic polymerisation of the bulk of material. Precautions and procedures for storage and use of monomers with or without the presence of inhibitors are discussed in detail. Examples cited are acrylic acid, acrylonitrile, butadiene, 2-chlorobutadiene, chlorotrifluoroethylene, methyl methacrylate, styrene, tetraflu-oroethylene, vinyl acetate, vinylacetylene, vinyl chloride, vinylidene chloride and vinylpyridine [1]. 

Thioketones, such as thiofluorenone, hexafluorothioacetone and perfluorocyclobutanone, add to a variety of 1,3-dienes to give dihydrothiapyrans (e.g. equation 24)25. Styrene yields a 1 2 adduct with hexafluorothioacetone (equation 25)25. The reactions of thioace-tophenone and thiobenzophenone with isoprene and 2-chlorobutadiene yield mixtures of regioisomers in quantitative yields (e.g. equation 26)26. 

Synonyms CCRIS 873 Chlorobutadiene 2-Chlorobutadiene-l,3 2-Chlorobuta-1,3-diene 2-Chloro-1,3-butadiene p Chloroprene EINECS 204-818-0 Neoprene NSC 18589 UN 1991. 

Chlorobenzamine, see 4-Chloroaniline p-Chlorobenzamine, see 4-Chloroaniline Chlorobenzol, see Chlorobenzene 2-Chlorobenzylidenemalononitrile, see o Chlorobenzylidenemalononitrile 2-Chlorobmn, see o-Chlorobenzylidenemalononitrile Chlorobromoform, see Dibromochloromethane Chlorobromomethane, see Bromochloromethane Chlorobutadiene, see Chloroprene 2-Chlorobutadiene-l,3, see Chloroprene 2-Chlorobuta-l,3-diene, see Chloroprene... 

Clary JJ, et al Toxicity of p-chloroprene (2-chlorobutadiene-1,3) Acute and subacute toxicity. Toxicol Appl Pharmacol 46 375-384, 1978... 

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

Culik, R., Kelly, D.R Clary, J.J. (1978) Inhalation studies to evaluate the teratogenic and embiyotoxic potential of 3-chloroprene (2-chlorobutadiene-1.3). Toxicol, appl. Pharmacol, 44,81-88... 

Liq vinyl acetylene is used as a raw material to make chloroprene rubber by addn of cold HQ, forming 2-chlorobutadiene-l, 3 which is then appropriately polymerized to form the desired product (Refs 6 8)... 

Fig. 15.16. Thermal cycloadditions of chloroprene (2-chlorobutadiene) I product distribution.

Many solvents form dangerous levels of peroxides during storage e.g., dipropyl ether, divinylacetylene, vinylidene chloride, potassium amide, sodium amide. Other compounds form peroxides in storage but concentration is required to reach dangerous levels e.g., diethyl ether, ethyl vinyl ether, tetrahydrofuran, p-dioxane, l,l-diethox) eth-ane, ethylene glycol dimethyl ether, propyne, butadiene, dicyclopentadiene, cyclohexene, tetrahydronaphthalenes, deca-hydrona-phthalenes. Some monomeric materials can form peroxides that catalyze hazardous polymerization reactions e.g., acr) lic acid, acr)Ionitrile, butadiene, 2-chlorobutadiene, chlorotrifluoroethylene, methyl methacrylate, styrene, tetrafluoroethylene,... 

RMn(CO)5, on the other hand, yields a 7r-allylic complex (42, 43, 249). Interaction of 2-chlorobutadiene (18) or 2-chlorobutene (20) with Mn(II) has been reported to form the corresponding tt complex. 

CHLOR-l,3-BUTADIEN (German) or CHLOROBUTADIENE or 2-CHLOROBUTADIENE or 2-CHLORO-... 

The first polymerization of isoprene in sealed bottles was reported in 1884 by Tilden. Methyl rubber was thermally polymerized at 70°C — the reaction required 3 to 6 months, giving poor quality products. In 1926 BASF developed sodium-initiated polymerization of butadiene known as Buna (for BUtadiene -I- Natrium). The first successful, general purpose rubbers were copolymers of butadiene with either styrene, Buna-S, or acrylonitrile, Buna-N [Tschunkur and Bock, 1933 Komad and Tschunkur, 1934]. Poly(2-chlorobutadiene), chloroprene [Carothers et ah, 1931], was introduced in 1931 by DuPont. Elastomeric polysulfides [Patrick, 1932] were... 

Vinylacetylene can be hydrochlorinated in a continuous manner in the presence of an aqueous cuprous chloride solution. The principal reaction is the formation of chloroprene, 2-chlorobutadiene-l,3. 

Many hundreds of diene polymers were investigated for their suitability as elastomers. Only three of these have achieved widespread commercial acceptance butadiene-styrene copolyipers, butadiene-aciylonitrile copolymers, and poly-2-chlorobutadienes. Other essentially non-diene elastomers such as butyl rubber from isobutene, Thiokol from ethylene dihalides and polysulfides, and silicones have become important for special applications. 

Syntheses of Dienes. The original process for preparing monovinyl-acetylene from acetylene is still used as the first step in the manufacture of 2-chlorobutadiene. Monovinlyacetylene is then reacted with hydrogen chloride to form the 2-chlorobutadiene according to the process described by Carothers. The two steps are illustrated as follows ... 

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