Synthesis chloroethene

The only other alkenyl carbenoid with a proton trans to the halide that can readily be generated by deprotonation is the parent 1-lithio-l-chloroethene 57 [43] (Scheme 3.13). Insertion into organozirconocenes arising from hydrozirconation of alkenes and alkynes, followed by protonation, affords terminal alkenes and ( )-dienes 59, respectively [38]. The latter provides a useful complement to the synthesis of 54 in Scheme 3.12 since the stereocontrol is >99%. 

The reactivity order also appears to correlate with the C-X bond energy, inasmuch as the tertiary alkyl halides both are more reactive and have weaker carbon-halogen bonds than either primary or secondary halides (see Table 4-6). In fact, elimination of HX from haloalkenes or haloarenes with relatively strong C-X bonds, such as chloroethene or chlorobenzene, is much less facile than for haloalkanes. Nonetheless, elimination does occur under the right conditions and constitutes one of the most useful general methods for the synthesis of alkynes. For example,... 

Apart from copper(I)-mediated reactions, few studies of the treatment of vinyliodonium salts with carbanions have appeared. The vinylations of the 2-phenyl- and 2- -hexyl-l,3-indandionate ions shown in equations 222 and 223 are the only reported examples of vinyliodonium-enolate reactions known to this author26,126. ( ,)-l-Dichloroiodo-2-chloroethene has been employed with aryl- and heteroarvllithium reagents for the synthesis of symmetrical diaryliodonium salts (equation 224)149,150. These transformations are thought to occur via the sequential displacement of both chloride ions with ArLi to give diaryl (/ -chlorovinyl)iodanes which then decompose with loss of acetylene (equation 225). That aryl(/ -chlorovinyl)iodonium chlorides are viable intermediates in such reactions has been shown by the conversion of ( )-(/ chlorovinyl)phenyliodonium chloride to diaryliodonium salts with 2-naphthyl- and 2-thienyllithium (equation 226)149,150. 

Three examples of the many reactions that can be advantageously carried out in high-temperature molten salts have been selected to illustrate this molten-salt technique. When 1,1-dichloroethane is passed through a ZnCl2/KCl melt at 330 °C, chloroethene is formed in 97 cmol/mol yield by dehydrohalogenation. Likewise, the addition of hydrogen chloride to acetylene proceeds with 89 cmol/mol yield in the same melt. A combination of these two steps allows a ready synthesis of the technically important chloroethene from acetylene and 1,1-dichloroethane according to Eq. (3-1) [25, 31]. 

Washburn has provided further detailed evidence to substantiate his claim to the synthesis of bicyclo[3,l,0]hexatriene, and cyclopropene intermediates are also involved in the photodecomposition of tosylhydrazide (nO). " Dehydrochlorination of (383) (synthesized by the addition of chloromethylcarbene to chloroethene) with t-butoxide in THF affords (385) the previously unreported parent methylenecyclo-propene (384) is presumably involved. More compelling evidence for the intermediacy of (384) comes from the reaction between (386) and t-butoxide (Scheme 46). Me Cl... 

Poly(chloroethene), also known as PVC (polyvinyl chloride), is very widely used in all forms of construction materials, packaging, electrical cable sheathing and so on. It is one of the world s most important plastics. Its widespread use is, however, somewhat controversial as its synthesis is associated with some toxic by-products known as dioxins which must be very carefully contained. Dioxins (Chapter 22) are linked to reproductive disorders and a variety of... 

Chlorine is the most important halogen. About 40 million tonnes are consumed each year, mainly in the synthesis of organochlorine compounds, many of which are used as solvents or converted into plastics. Figure 6.4 shows the distribution of chlorine consumption the largest single use is in the manufacture of chlorinated plastics. For example, it is used to make vinyl chloride (chloroethene) from ethylene (ethene) ... 

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