Vinyl dichlorides

Poly(vinyl dichloride) (rigid) Self-ext. 1.50-1.54. 007-008 Translucent to opaque... 

Coupling of vinyl dichlorides.1 This catalyst effects selective coupling of Grig-nard reagents or organozinc chlorides with only one of the chlorine atoms of 1,1-dichloro-l-alkenes (2) to give (Z)-vinyl chlorides (3). The selective coupling involves the chlorine that is trans to the R substituent, probably because of a steric... 

PEN has lower gas permeation coefficients than PET for carbon dioxide, oxygen and moisture for both film types. Although the gas-barrier properties of PEN are similar to those of poly(vinyl dichloride), it is not affected by moisture in the environment. Both oriented and unoriented PEN films restrict gas diffusion more... 

Polyolefines, like simple alkanes, can be chlorinated by chlorine giving hydrogen chloride and chlorinated products such as Tyrin, used as plasticizers and flame retardants, and poly (vinyl dichloride), which has better heat resistance than PVC and is used for hot water piping. 

Organolithium compounds can also induce the rearrangement of 1,1-diaiyl vinyl dichlorides and dibromides (Fritsch-Buttenberg-Wiechell rearrangement) to diarylalkynes p,p -bridged cyclic diaiylal-kynes ° can be prepared via this route (Scheme 59). 

As a test of the intennediacy of the divinyl dichloride (44) in the solvolysis of dichlorocyclopropylcar-binols, Hiyama prepared the homoallylic alcohols (48) by addition of 1,1 -dichloroallyllithium to cyclic ketones. Treatment of (48) with triflucnoacetic acid produced the cyclcqtentencmes in veiy good yield (equation 31).This reacdcm presumably proceeds by dehydration to the vinyl dichloride followed by a similar ionizaticHi-cyclization sequence, bterestingly the regioisomeric dichloride also underwent closure to a cyclopentenone. ... 

Rempp and Franta [3] described the synthesis of macromonomers either by using redox catalysis with halogenated monomers (vinyl chloride, vinyl dichloride, or even trifluorochloroethylene) or by using a radical initiation with (meth)acrylates. In the latter case, thiol compounds were used as transfer agents (Scheme 46) [251] ... 

If chlorination is carried out below 65 C in the presence of a diluent that swells but does not dissolve the polymer, the formation of products with chlorines on all adjacent carbons is promoted. Dannis and Ramp (30) have shown that products prepared by this technique have higher T values and greater heat resistance than products prepared at higner chlorination temperatures. The change in T as a result of increased chlorine content in such low-temperature chlorinations is shown in Figure 25. The high T shown for poly(vinyl dichloride) is not that of poly(vinylidene chrorlde). 

The analogy with alkene chemistry can be continued in that alkynes react with bromine, chlorine, or iodine, but only one of the two Ji-bonds is used. The reaction is known as dihalogenation of alkynes. When 2-hexyne reacts with chlorine (CI2), the alkyne reacts as a Lewis base and the isolated product is the vinyl dichloride 110 (J5-l,2-dichloro-l-pentene). Formation of this product is explained by an intermediate vinyl-chloronium ion, 109, which is analogous to the halonium ions formed from alkenes in Section 10.4.1. As with alkenes, the chloronium ion reacts with the nucleophihc chloride ion (CL) via anti attack... 

Most of the ethylene dichloride produced is utilized for the manufacture of vinyl chloride, which may be obtained from it by pyrolysis or the action of caustic soda. Large quantities are also used in anti-knock additives for gasoline. As a solvent It has been displaced by trichloroethylene and tetrachloroelhyJene. U.S. production 1978 4-75 megatonnes. 

C/760 mmHg) sulfur dichloride After the addition stirring v/as stopped and the flask was allowed to stand for 15 h in the ice-bath. The condenser was replaced with a drying tube containing CaCl (refluxing of the vinyl chloride had stopped completely after the addition of sulfur dichloride). 

Once the principal route to vinyl chloride, in all but a few percent of current U.S. capacity this has been replaced by dehydrochlorination of ethylene dichloride. A combined process in which hydrogen chloride cracked from ethylene dichloride was added to acetylene was advantageous but it is rarely used because processes to oxidize hydrogen chloride to chlorine with air or oxygen are cheaper (7) (see Vinyl polymers). 

Chlorine cannot be stored economically or moved long distances. International movements of bulk chlorine are more or less limited to movements between Canada and the United States. In 1987, chlorine moved in the form of derivatives was 3.3 million metric tons or approximately 10% of total consumption (3). Exports of ethylene dichloride, vinyl chloride monomer, poly(vinyl chloride), propylene oxide, and chlorinated solvents comprise the majority of world chlorine movement. Countries or areas with a chlorine surplus exported in the form of derivatives include Western Europe, Bra2il, USA, Saudi Arabia, and Canada. Countries with a chlorine deficit are Taiwan, Korea, Indonesia, Vene2uela, South Africa, Thailand and Japan (3). 

Chlorine reacts with saturated hydrocarbons either by substitution or by addition to form chlorinated hydrocarbons and HCl. Thus methanol or methane is chlorinated to produce CH Cl, which can be further chlorinated to form methylene chloride, chloroform, and carbon tetrachloride. Reaction of CI2 with unsaturated hydrocarbons results in the destmction of the double or triple bond. This is a very important reaction during the production of ethylene dichloride, which is an intermediate in the manufacture of vinyl chloride ... 

Ethylene dichloride, vinyl chloride monomer, trichloroethylene, perchloroethylene. 

Ethylene Dichlonde and Vinyl Chloride. In the United States, all ethylene dichloride [107-60-2] (EDC) is produced from ethylene, either by chlorination or oxychlorination (oxyhydrochlorination). The oxychlorination process is particularly attractive to manufacturers having a supply of by-product HCl, such as from pyrolysis of EDC to vinyl chloride [75-01-4] monomer (VCM), because this by-product HCl can be fed back to the oxychlorination reactor. EDC consumption follows demand for VCM which consumed about 87% of EDC production in 1989. VCM is, in turn, used in the manufacture of PVC resins. Essentially all HCl generated during VCM production is recycled to produce precursor EDC (see Chlorocarbons and Cm OROHYDROCARBONS ViNYLPOLYAffiRS). 

Ethylene Dichloride Pyrolysis to Vinyl Chloride. Thermal pyrolysis or cracking of EDC to vinyl chloride and HCl occurs as a homogenous, first-order, free-radical chain reaction. The accepted general mechanism involves the four steps shown in equations 10—13 ... 

Chlorination of various hydrocarbon feedstocks produces many usehil chlorinated solvents, intermediates, and chemical products. The chlorinated derivatives provide a primary method of upgrading the value of industrial chlorine. The principal chlorinated hydrocarbons produced industrially include chloromethane (methyl chloride), dichloromethane (methylene chloride), trichloromethane (chloroform), tetrachloromethane (carbon tetrachloride), chloroethene (vinyl chloride monomer, VCM), 1,1-dichloroethene (vinylidene chloride), 1,1,2-trichloroethene (trichloroethylene), 1,1,2,2-tetrachloroethene (perchloroethylene), mono- and dichloroben2enes, 1,1,1-trichloroethane (methyl chloroform), 1,1,2-trichloroethane, and 1,2-dichloroethane (ethylene dichloride [540-59-0], EDC). 

Dichloroethane [107-06-2] ethylene chloride, ethylene dichloride, CH2CICH2CI, is a colorless, volatile Hquid with a pleasant odor, stable at ordinary temperatures. It is miscible with other chlorinated solvents and soluble in common organic solvents as well as having high solvency for fats, greases, and waxes. It is most commonly used in the production of vinyl chloride monomer. 

The leading derivative of ethylene dichloride is vinyl chloride [75-01-4] monomer (VCM), which is subsequently used to produce poly(vinyl chloride) and chloriaated hydrocarbons. Viayl chloride is obtaiaed by dehydrochloriaatioa of ethyleae dichloride ia the gas phase (500—600°C and 2.5—3.5 MPa). 

The per pass ethylene conversion in the primary reactors is maintained at 20—30% in order to ensure catalyst selectivities of 70—80%. Vapor-phase oxidation inhibitors such as ethylene dichloride or vinyl chloride or other halogenated compounds are added to the inlet of the reactors in ppm concentrations to retard carbon dioxide formation (107,120,121). The process stream exiting the reactor may contain 1—3 mol % ethylene oxide. This hot effluent gas is then cooled ia a shell-and-tube heat exchanger to around 35—40°C by usiag the cold recycle reactor feed stream gas from the primary absorber. The cooled cmde product gas is then compressed ia a centrifugal blower before entering the primary absorber. 

There are three general methods of interest for the preparation of vinyl chloride, one for laboratory synthesis and the other two for commercial production. Vinyl chloride (a gas boiling at -14°C) is most conveniently prepared in the laboratory by the addition of ethylene dichloride (1,2-dichloroethane) in drops on to a warm 10% solution of sodium hydroxide or potassium hydroxide in a 1 1 ethyl alcohol-water mixture Figure 12.1). At one time this method was of commercial interest. It does, however, suffer from the disadvantage that half the chlorine of the ethylene dichloride is consumed in the manufacture of common salt. 

The gases from the reactor are then cooled and subjected to a caustic wash to remove unreacted hydrogen chloride. This is then followed by a methanol wash to remove water introduced during the caustic wash. A final purification to remove aldehydes and ethylidene dichloride, formed during side reactions, is then carried out by low-temperature fractionation. The resulting pure vinyl chloride is then stored under nitrogen in a stainless steel tank. 

In addition to its water solubility poly(vinyl pyrrolidone) is soluble in a very wide range of materials, including aliphatic halogenated hydrocarbons (methylene dichloride, chloroform), many monohydric and polyhdric alcohols (methanol, ethanol, ethylene glycol), some ketones (acetyl acetone) and lactones (a-butyrolactone), lower aliphatic acids (glacial acetic acid) and the nitro-paraffins. The polymer is also compatible with a wide range of other synthetic polymers, with gums and with plasticisers. 

NOTE - Petrochemical plants also generate significant amounts of solid wastes and sludges, some of which may be considered hazardous because of the presence of toxic organics and heavy metals. Spent caustic and other hazardous wastes may be generated in significant quantities examples are distillation residues associated with units handling acetaldehyde, acetonitrile, benzyl chloride, carbon tetrachloride, cumene, phthallic anhydride, nitrobenzene, methyl ethyl pyridine, toluene diisocyanate, trichloroethane, trichloroethylene, perchloro-ethylene, aniline, chlorobenzenes, dimethyl hydrazine, ethylene dibromide, toluenediamine, epichlorohydrin, ethyl chloride, ethylene dichloride, and vinyl chloride. 

The chemistry of side reactions and by-products may also offer opportunities for increasing the inherent safety of a process. For example, a process involving a caustic hydrolysis step uses ethylene dichloride (EDC 1,2-dichloroethane) as a solvent. Under the reaction conditions a side reaction between sodium hydroxide and EDC produces small but hazardous quantities of vinyl chloride ... 

From the results obtained by thermal decomposition of both low-molecular weight vicinal dichlorides in the gas phase [74,75] and of the copolymers of vinyl chloride and /rthermal instability of PVC to the individual head-to-head structures. Crawley and McNeill [76] chlorinated m-1,4-polybutadiene in methylene chloride, leading to a head-to-head, and a tail-to-tail PVC. They found, for powder samples under programmed heating conditions, that head-to-head polymers had a lower threshold temperature of degradation than normal PVC, but reached its maximum rate of degradation at higher temperatures. 

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