Hydrochlorination

Ethyl Chloride. Most ethyl chloride [75-00-3] is produced by the hydrochlorination of ethylene (qv) using anhydrous HCl. Historically, the primary use of ethyl chloride was for the manufacture of tetraethyllead (TEL), a primary component of antiknock mixes in gasolines. Use has declined as a... 

Synthesis of P-Methylheptenone from Petrochemical Sources. p-MethyUieptenone (1) is an important intermediate in the total synthesis of terpenes. Continuous hydrochlorination of isoprene [78-79-5] produces prenyl chloride [505-60-6] which then reacts with acetone with a quaternary ammonium catalyst and sodium hydroxide to give P-methyUieptenone (6-methyIhept-5-en-2-one [110-93-0]) (eq. 1) (16—19). 

Nerol, geraniol, and linalool, known as the rose alcohols, are found widely in nature. Nerol and geraniol have mild, sweet odors reminiscent of rose flowers. They are manufactured by the hydrochlorination of mycene at the conjugated double bonds when a copper catalyst is used (88,89). 

Linalool can also be made along with nerol and geraniol via the hydrochlorination of myrcene. After conversion of the chlorides to acetates followed by saponification of the acetates, the mixture of alcohols is obtained. Fractionation of the mixture gives linalool in about 95% purity, but the presence of close boiling impurities prohibits manufacture of a perfiimery-quahty product. 

Hydrochlorination. The addition of hydrogen chloride to alkenes in the absence of peroxides takes place by an electrophilic substitution mechanism. The orientation is in accord -with Markovnikov s mle in -which the hydrogen atom adds to the side of the double bond that -will result in the... 

The hydrochlorination of olefins is a weaMy exothermic reaction with heats of reaction ranging from 4 to 21 kj/mol (1—5 kcal/mol). The hydrochlorination of acetylene is more exothermic, 184 kJ/mol (44 kcal/mol). 

LiquidPha.se. The methyl chloride process with the widest use in the United States is the Hquid-phase methanol hydrochlorination process. SHicone producers use methyl chloride in its manufacture and produce an aqueous hydrochloric acid stream as a by-product. This by-product HCl is converted back to methyl chloride by hydrochlorination. In fact, it is possible to produce methyl chloride directiy from the chioromethylsilane hydrolysis step in the siHcone process (18,19) (see Silicon compounds, silicones). 

Gas Phase. The gas-phase methanol hydrochlorination process is used more in Europe and Japan than in the United States, though there is a considerable body of Hterature available. The process is typicaHy carried out as foHows vaporized methanol and hydrogen chloride, mixed in equimolar proportions, are preheated to 180—200°C. Reaction occurs on passage through a converter packed with 1.68—2.38 mm (8—12 mesh) alumina gel at ca 350°C. The product gas is cooled, water-scmbbed, and Hquefied. Conversions of over 95% of the methanol are commonly obtained. Garnma-alurnina has been used as a catalyst at 295—340°C to obtain 97.8% yields of methyl chloride (25). Other catalysts may be used, eg, cuprous or zinc chloride on active alumina, carbon, sHica, or pumice (26—30) sHica—aluminas (31,32) zeoHtes (33) attapulgus clay (34) or carbon (35,36). Space velocities of up to 300 h , with volumes of gas at STP per hour per volume catalyst space, are employed. 

Production and sales data for methyl chloride, as reported by the U.S. International Trade Commission for the years 1945 to 1989, are given in Table 3. Production grew tremendously in the 1960s and again in the late 1980s. Methanol hydrochlorination was used to produce about 64% of the methyl chloride in 1969 and about 98% by 1974. The principal U.S. producers and their capacities are shown in Table 4 (54). These capacities do not include the 100 + million kg per year used by The Dow Chemical Company, Occidental, and Vulcan to captively produce other chloromethanes. 

Three industrial processes have been used for the production of ethyl chloride hydrochlorination of ethylene, reaction of hydrochloric acid with ethanol, and chlorination of ethane. Hydrochlorination of ethylene is used to manufacture most of the ethyl chloride produced in the United States. Because of its prohibitive cost, the ethanol route to ethyl chloride has not been used commercially in the United States since about 1972. Thermal chlorination of ethane has the disadvantage of producing undesired by-products, and has not been used commercially since about 1975. 

Hydrochlorination of Ethylene. The exothermic vapor-phase reaction between ethylene [74-85-1] and hydrogen chloride [7647-01-0] can be carried out at 130—250°C under a variety of catalytic conditions. Yields are reported to be greater than 90% of theoretical (14). 

Significant quantities of ethyl chloride are also produced as a by-product of the catalytic hydrochlorination over a copper chloride catalyst, of ethylene and hydrogen chloride to produce 1,2-dichloroethane, which is used as feedstock in the manufacture of vinyl choride (see Vinyl polymers). This ethyl chloride can be recovered for sale or it can be concentrated and catalyticaHy cracked back to ethylene and hydrogen chloride (25). As the market for ethyl chloride declines, recovery as an intermediate by-product of vinyl chloride manufacture may become a predominant method of manufacture of ethyl chloride. 

In the most important process, vinyl chloride obtained from 1,2-dichloroethane is hydrochlorinated to 1,1-dichloroethane which is then thermally or photochemicaHy chlorinated ... 

Other routes to 1,1,2-trichloroethane are chlorination of acetylene in the presence of HCl (101) and chlorination of vinyl chloride at room temperatures with FeCl (102—104), hydrochlorination of cis- and /n j -l,2-dichloroethylene with FeCl catalyst (105), vapor-phase oxychlorination of... 

Tetrachloroethane is often an incidental by-product in the manufacture of chlorinated ethanes. It can be prepared by heating the 1,1,2,2-isomer with anhydrous aluminum chloride or chlorination of 1,1-dichloroethylene at 40°C (118). Hydrochlorination of trichloroethylene using a FeCl catalyst may also be used. 

Dicbloro-l,3-butadiene [1653-19-6] is a favored comonomer to decrease the regularity and crystallization of chloroprene polymers. It is one of the few monomers that will copolymerize with chloroprene at a satisfactory rate without severe inhibition. It is prepared from by-products or related intermediates. It is also prepared in several steps from chloroprene beginning with hydrochlorination. Subsequent chlorination to 2,3,4-trichloto-1-butene, followed by dehydrochlorination leads to the desired monomer in good yield if polymerization is prevented. 

Halogenation and dehalogenation are catalyzed by substances that exist in more than one valence state and are able to donate and accept halogens freely. Silver and copper hahdes are used for gas-phase reactions, and ferric chloride commonly for hquid phase. Hydrochlorination (the absoration of HCl) is promoted by BiCb or SbCl3 and hydrofluorination by sodium fluoride or chromia catalysts that form fluorides under reaction conditions. Mercuric chloride promotes addition of HCl to acetylene to make vinyl chloride. Oxychlori-nation in the Stauffer process for vinyl chloride from ethylene is catalyzed by CuCL with some KCl to retard its vaporization. 

By-product HCl may be used for the hydrochlorination of ethylene to produce more ethyl chloride. Hydrochlorination of ethylene, however, is the main route for the production of ethyl chloride ... 

In the chemical process industry molybdenum has found use as washers and bolts to patch glass-lined vessels used in sulphuric acid and acid environments where nascent hydrogen is produced. Molybdenum thermocouples and valves have also been used in sulphuric acid applications, and molybdenum alloys have been used as reactor linings in plant used for the production of n-butyl chloride by reactions involving hydrochloric and sulphuric acids at temperatures in excess of 170°C. Miscellaneous applications where molybdenum has been used include the liquid phase Zircex hydrochlorination process, the Van Arkel Iodide process for zirconium production and the Metal Hydrides process for the production of super-pure thorium from thorium iodide. 

Hutchings, G.J. (1985) Vapor phase hydrochlorination of acetylene Correlation of catalytic activity of supported metal chloride catalysts. Journal of Catalysis, 96, 292-295. 

In another study, it was shown that the activity of hydrochlorination catalysts made by impregnation of activated carbon with tetrachloroaureate is due to the adsorption of [AuCy anions on the activated carbon [423]. Similar studies, dealing with the adsorption of aurocyanide, [Au(CN)2] , onto activated carbon, have revealed that aurocyanide does not convert to metallic gold up to temperature of about 240°C [424, 425]... 

Another convenient procedure for hydrochlorination involves adding trimethylsilyl chloride to a mixture of an alkene and water. Good yields of HC1 addition products (Markovnikov orientation) are formed.3 4 These conditions presumably involve generation of HC1 by hydrolysis of the silyl chloride, but it is uncertain if the silicon plays any further role in the reaction. 

Hydrochlorination of the same substrate leads to the cyclic unstable phospho-nium salt 141 (Scheme 57) [103],... 

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