Chlorinating agent

Antimony peniachloride, SbCls. M.p. TC, b.p. 79 C (Sb or SbCIa plus CI2). Readily hydrolysed by water, forms complexes, e.g. [SbClft]". Mixed antimony(III)/(V) complexes occur as salts M2SbCl6. SbCls is used extensively as a chlorinating agent. 

Selenium monochloride, Se2Cl2 m.p. —85 C 130°C (decomp.). Reddish liquid, a good chlorinating agent (CI2 plus Se). 

Antimony(V) chloride is a fuming liquid, colourless when pure, m.p. 276 K. It is a powerful chlorinating agent. 

Sulphur oxide dichloride is used as a chlorinating agent in organic chemistry, for example in the preparation of acid chlorides ... 

Chloroacetyl chloride is manufactured by reaction of chloroacetic acid with chlorinating agents such as phosphoms oxychloride, phosphoms trichloride, sulfuryl chloride, or phosgene (42—44). Various catalysts have been used to promote the reaction. Chloroacetyl chloride is also produced by chlorination of acetyl chloride (45—47), the oxidation of 1,1-dichloroethene (48,49), and the addition of chlorine to ketene (50,51). Dichloroacetyl and trichloroacetyl chloride are produced by oxidation of trichloroethylene or tetrachloroethylene, respectively. 

Uses.l Phosphoms pentachloride is used in the manufacture of chlorophospha2enes, and serves as a catalyst and a chlorinating agent in organic syntheses. 

Phosphoms trichloride is also used in the manufacture of antifoam agents, catalysts, dyes and pigments, as well as pharmaceutical and quaternary compounds, and is commonly used as a chlorinating agent. Phosphoms trichloride is used to make phosphoms oxychloride, which is used in the manufacture of adsorbents for air filters, antifoam agents, dyes and pigments, mineral-processing materials, pharmaceuticals (qv), and solvents. These uses represented 32,000 t of PCl in 1988 and 30,000 t in 1994. 

Sulfur monochloride can act as a chlorinating agent in some reactions. For example, 0,0-diaLkyl phosphorodithioic acids [756-80-9] are converted to 0,0-diaLkylphosphorochloridothioate ... 

The organic chemistry of sulfuryl chloride involves its use in chlorination and sulfonation (172,175,196,197). As a chlorinating agent, sulfuryl chloride is often mote selective than elemental chlorine. The use of sulfuryl chloride as a chlorinating agent often allows mote convenient handling and measurement as well as better temperature control because of the lower heat of reaction as compared with chlorine. Sulfuryl chloride sometimes affords better selectivity than chlorine in chlorination of active methylene compounds (198—200) ... 

Uses. Most apphcations of MSC are for intermediates in the pharmaceutical, photographic, fiber, dye, and agricultural industries. There also are miscellaneous uses as a stabdizer, catalyst, curing agent, and chlorination agent. 

Other mechanisms, involving initial formation of ethylene oxide [75-21-8] as the possible rate-limiting step, complexation of CuC with HCl (92), and C as the chlorinating agent (93) have been suggested. 

Heated zirconium is readily chlorinated by ammonium chloride, molten stannous chloride, zinc chloride, and chlorinated hydrocarbons and the common chlorinating agents. It is slowly attacked by molten magnesium chloride in the absence of free magnesium, which is always present in the KroU process. 

This is foUowed by a second reaction where sulfur monochloride becomes the chlorinating agent ... 

Uses. /-Butyl hypochlorite has been found useful in upgrading vegetable oils (273) and in the preparation of a-substituted acryflc acid esters (274) and esters of isoprene halohydrins (275). Numerous patents describe its use in cross-linking of polymers (qv) (276), in surface treatment of mbber (qv) (277), and in odor control of polymer latexes (278). It is used in the preparation of propylene oxide (qv) in high yield with Httle or no by-products (269,279). Fluoroalkyl hypochlorites are useful as insecticides, initiators for polymerizations, and bleaching and chlorinating agents (280). 

Dehydrochlorination of 1,1,2-trichloroethane at 500°C in the presence of a copper catalyst gives a different product, ie, cis- and /n7 j -l,2-dichloroethylene. Addition of small amounts of a chlorinating agent, such as chlorine, promotes radical dehydrochlorination in the gas phase through a disproportionation mechanism that results in loss of hydrogen chloride and formation of a double bond. The dehydrochlorination of 1,2-dichloroethane in the presence of chlorine, as shown in equations 19 and 20, is a typical example. 

Continuous chlorination of benzene at 30—50°C in the presence of a Lewis acid typically yields 85% monochlorobenzene. Temperatures in the range of 150—190°C favor production of the dichlorobenzene products. The para isomer is produced in a ratio of 2—3 to 1 of the ortho isomer. Other methods of aromatic ring chlorination include use of a mixture of hydrogen chloride and air in the presence of a copper—salt catalyst, or sulfuryl chloride in the presence of aluminum chloride at ambient temperatures. Free-radical chlorination of toluene successively yields benzyl chloride, benzal chloride, and benzotrichloride. Related chlorination agents include sulfuryl chloride, tert-huty hypochlorite, and /V-ch1orosuccinimide which yield benzyl chloride under the influence of light, heat, or radical initiators. 

Hexachloroethane has been suggested as a degasifter in the manufacture of aluminum and magnesium metals. Hexachloroethane has been used as a chain-transfer agent in the radiochemical emulsion preparation of propylene tetrafluoroethylene copolymer (152). It has also been used as a chlorinating agent in the production of methyl chloride from methane (153). 

Chlorination with Other Reagents. Chlorotoluenes can also be obtained in good yields by the reaction of toluene with stoichiometric proportions of certain Lewis acid chlorides such as inon(III) chloride, as the chlorinating agent (51). Generally, the product mixture contains /)-chlorotoluene as the principal component. Several modifications have been proposed to improve product yields (52,53). 

An 80% yield of benzyl chloride is obtained with sulfuryl chloride as chlorinating agent. Yields of >70% of benzyl chloride are obtained by the zinc chloride-catalyzed chloromethylation of benzene but formation of bis-chloromethyl ether presents a health hazard for this reaction pathway. 

Other chlorinating agents, such as pentachlorocyclohexadienone, have been subjected to laboratory study to make it possible to select each of the isomers (19). The use of 2,3,4,5,6,6-hexachlorocyclohexa-2,4-dien-l-one [21306-21 -8] makes chlorination possible in the ortho position. 

Dichlorophenols. Among all the dichlorophenols, C H Cl O, it is 2,4-dichlorophenol that is produced in greatest quantity. 2,4-Dichlorophenol is used in manufacturing 2,4-dichlorophenoxyacetic acid [94-75-7] (2,4-D) and 2-(2,4-dichlorophenoxy)propionic acid [720-36-5] (2,4-DP). Industrially, 2,4-dichlorophenol can be obtained by chlorinating phenol, -chlorophenol, o-chlorophenol, or a mixture of these compounds in cast-iron reactors. The chlorinating agent may be chlorine or sulfuryl chloride in combination with a Lewis acid. For example ... 

Hypochlorous acid is a weak chlorinating agent. In acidic solution, it is converted to a much more active chlorinating agent Although early mechanistic studies suggested that Cl" " might be formed under these conditions, it has since been shown that this is not the... 

A highly selective photochemical chlorination of esters, amides, and alcohols can be effected in 70%-90% H2SO4 using A-chlorodialkylamines as chlorinating agents. Mechanistic studies indicate that a chain reaction is involved ... 

The vinylic fluorine of perfluoroisobutylene can be replaced with chlorine by using phosphorus oxychloride or henzoyl chloride however, somewhat different mixtures result from these two chlorinating agents [72] (equation 59). 

Chloroquinazoline can be isolated, at best in 40% yield, by boiling 2-hydroxyquinazoline with phosphorus pentachloride in phosphorus oxychloride for 45 min, and attempts to improve this yield have proved fruitless. The yields are much higher when an aryl group is in position 4 w hich suggests an attack of the 3,4-double bond in 2-hydroxy- and 2-chloro-quinazolines by the chlorinating agent. 

Another decarboxylation reaction that employs lead tetraacetate under milder conditions, has been introduced by Grob et alJ In that case A-chlorosuccinimide is used as chlorinating agent and a mixture of A,A-dimethylformamide and acetic acid as solvent. 

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