Chloroethene, preparation

For trichloroethene (TCE), the stoichiometric amount of iron and the effect of different preparations determine the outcome of the several competing reactions. Coupling products such as butenes, acetylene and its reduction products ethene and ethane, and products with five or six carbon atoms were formed (Liu et al. 2005). Although a held-scale application successfully lowered the concentration of TCE, there was evidence for the formation of the undesirable di-l,2-dichloroethene and 1-chloroethene (vinyl chloride) in the groundwater (Quinn et al. 2005). 

The most readily available alkenyl halide is chloroethene (vinyl chloride), which can be prepared by a number of routes ... 

Vinyliodonium ions, 35 and 36, are hypervalent iodine species in which one or two alkenyl ligands are bound to a positively charged iodine(III) atom. Although they are reactive with nucleophilic reagents, they are less labile than alkynyliodonium ions, and stable halide salts of vinyliodonium ions can be prepared. The first vinyliodonium compounds [i.e. (a, / -dichlorovinyl)iodonium salts] were synthesized by the treatment of silver acetylide-silver chloride complexes with (dichloroiodo)arenes or l-(dichloroiodo)-2-chloroethene in the presence of water (equation 152). The early work was summarized by Willgerodt in 1914115. This is, of course, a limited and rather impractical synthetic method, and some time elapsed before the chemistry of vinyliodonium salts was developed. Contemporary synthetic approaches to vinyliodonium compounds include the treatment of (1) vinylsilanes and vinylstannanes with 23-iodanes, (2) terminal alkynes with x3-iodanes, (3) alkynyliodonium salts with nucleophilic reagents and (4) alkynyliodonium salts with dienes. 

Chloro-l fluoroethane (10) is prepared by treating chloroethene with anhydrous hydrogen fluoride ° in the vapor phase at 20-70 C in the presence of a catalyst consisting of active charcoal impregnated with 10-45 % by weight fluorosulfonic acid or with hydrogen fluoride/ titanium(IV) chloride. ... 

Problem 32,15 Although both polymers arc prepared by free-radical processes, poly(vinyl chloride) is amorphous and poly(vinylidcne chloride) (Saran) is highly crystalline. How do you account for the difference (Vinylidenc chloride is 1,1-di-chloroethene.)... 

Using mercury derivatives, 1-bromo-l-chlorocyclopropanes are prepared from alkenes of low reaetivity, such as fluoro- and chloroethene, 1,1-difluoro-, tri- and tetrafluoroethene, tetrachloroethene, etc. In the case of some alkenes, C —H insertion of bromochlorocarbene competes effectively with cycloaddition, e.g. formation of 14 and 15. ... 

The unsubstituted diselenin 111 could be prepared in up to 24% yield by direct reaction of r-l,2-chloroethene with sodium selenide in acetonitrile in the presence of a crown ether (Equation 31) <2005JOC5036>. Although many congeners form, under certain circumstances 111 predominates. It is interesting to note that the sodium selenide used in this preparation could be prepared at room temperature by reaction of selenium with sodium hydroxide and Rongalit (sodium hydroxymethanesulfmate). 

At the reaction temperature of 400 C, dechlorinated products of TCEa consisted of chloroethene (VCM), 1,1-dichloroethylene, trans-1,2- and cis-l,2-dichloroethylene (DCE) for the tested catalysts. However, the main product was changed with types of metal loaded in the catalysts. VCM was the main product in the cases of Ni catalysts (Ni-L-CS, Ni-L-SBA and Ni-E-SBA), while cis-l,2-DCE was a main product for the Mo catalyst (HP318). Since the VCM is a raw material for the PVC production, selectivity for VCM and conversion of TCEa could be used as important factors to compare the catalyst performances. It was observed (Fig. 4 (a)) that the prepared catalysts were deactivated faster than the commercial catalyst. Catalysts prepared using APTES and LIX-984 showed a better life-time than the catalysts prepared using EDTA. It was believed that Ni-L-SBA catalyst was lasted longer than the Ni-L-CS catalyst due to the uniform pore structures. In addition, prepared catalysts showed a better selectivity for VCM than that of commercial catalyst (Fig. 4 (b)). 

The haloalkenes, for example, chloroethene [ethylene chloride, C1(H)C=CH2], prepared in this and related ways and discussed in more detail with the other organic halides (Chapter 7) serve as starting material for a host of other types of compounds. However, additional substitution reactions (also apparently occurring through addition-elimination pathways) might be effected. Typical of these is the apparent arylation of an alkene in which an aryl group is substituted for a hydrogen attached to the double bond. The process is known as the Heck reaction and is shown in Scheme 6.54. ... 

Ethenyllithium (vinyllithium) is not generally prepared by direct deprotonation of ethene but rather from chloroethene (vinyl chloride) by metallation (Section 8-7). 

Chloroethene, the monomer for the production of PVC, was originally prepared by the addition of HCl to ethyne. However, ethyne is very much more expensive than ethene. How could you prepare chloroethene from ethene in an economical process ... 

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