Promoters hydrogen chloride

The reaction of a fourfold excess of aryldiazomethanes 130 with dichlorosulfine leads to 3,5-diaryl[l,2,4]triazolo[5,l+]-[l,3,4]thiadiazole-4-oxides 131. The formation of the fused heterocycles 131 is rationalized on the basis of two consecutive cycloaddition steps, each followed by elimination of hydrogen chloride promoted by the excess of aryldiazomethane (Scheme 9) <1984JCM175>. 

The higher-boiling products obtained in the hydrogen chloride-promoted reaction consisted chiefly of... 

Other Cycloalkanes. Hydrogen chloride promoted monoethylation of other cycloparaffins (e.g., cyclopentane, methylcyclopentane and methylcyclohexane) and many paraffins (e.g., propane, isobutane, n -pentane, isopentane, 2,2-dimethylbutane, 2,3-dimethylbutane, n-heptane and 2,2,4-trimethylpentane). 

It may be concluded that primary alkyl chlorides undergo peroxide-induced, hydrogen chloride-promoted, alkylation with ethylene to yield products formed by alkylation at a tertiary carbon atom, at a penultimate secondary carbon atom, or at a primary carbon atom holding a chlorine atom. In the absence of hydrochloric acid, n-butyl chloride underwent little peroxide-induced reaction with ethylene presumably because hydrogen chloride is necessary for propagating the reaction chain via abstraction of hydrogen from the hydrogen chloride to produce the ethylated product and a chlorine atom which maintains the chain by abstraction from the alkyl chloride. 

The solution should be neutral before distillation. The presence of hydrogen chloride promotes decomposition of phosphoric esters into phosphoric acid and alkenes. The benzene solution should not be washed with alkaline reagents, such as sodium carbonate solution, since alkaline reagents also cause decomposition during distillation. 

With aluminum chloride catalysts, on the other hand, the reaction proceeds chiefly via the addition of (-butyl chloride to the original butene before more than a relatively minor portion of the latter can react with the hydrogen chloride promoter to yield s-butyl chloride. Therefore, the two 7i-butylenes yield very different alkylates. 

Further evidence that addition of hydrogen chloride promoter has a beneficial effect may be seen in the fact that catalyst life is greatly increased. 

The decomposition of a relatively unstable alkyl hypochlorite (e.g., to a ketone) produces hydrogen chloride, promoting fiirther reaction. However, an excess of hydrogen chloride is not permitted because the carbonyl derivatives then become eno-lized and further chlorinated, resulting in the formation of chloroketones. Therefore... 

Liquid-Ph se Processes. Prior to 1980, commercial hquid-phase processes were based primarily on an AIQ. catalyst. AIQ. systems have been developed since the 1930s by a number of companies, including Dow, BASF, Shell Chemical, Monsanto, SociStH Chimique des Charboimages, and Union Carbide—Badger. These processes generally involve ethyl chloride or occasionally hydrogen chloride as a catalyst promoter. Recycled alkylated ben2enes are combined with the AIQ. and ethyl chloride to form a separate catalyst—complex phase that is heavier than the hydrocarbon phase and can be separated and recycled. 

Oxychlorination of Ethylene to Dichloroethane. Ethylene (qv) is converted to dichloroethane in very high yield in fixed-bed, multitubular reactors and fluid-bed reactors by reaction with oxygen and hydrogen chloride over potassium-promoted copper(II) chloride supported on high surface area, porous alumina (84) ... 

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. 

Diaziridinones (167) are obtained from di-t-alkylureas by Af-chlorination and base-promoted elimination of hydrogen chloride from (279) (69JOC2254). The very unstable c/s-fused diaziridinone (280) could be prepared by a similar but milder procedure (76JOC2813). 

It is necessary to remove the hydrogen chloride because it promotes decomposition of the dibromoether. 

The demand for aviation gasoline during World War II was so great that isobutanc from alkylation feedstock was insufficient. This deficiency was remedied by isomerization of abundant normal butane into isobutane using the isomerization catalyst aluminum chloride on alumina promoted by hydrogen chloride gas. 

Dehydrochlorination of bis(tnfluoromethylthio)acetyl chloride with calcium oxide gives bis(trifluoromethylthio)ketene [5] (equation 6) Elimination of hydrogen chloride or hydrogen bromide by means of tetrabutylammonium or potassium fluoride from vinylic chlorides or bromides leads to acetylenes or allenes [6 (equation 7) Addition of dicyclohexyl-18-crown-6 ether raises the yields of potassium fluoride-promoted elimination of hydrogen bromide from (Z)-P-bromo-p-ni-trostyrene in acetonitrile from 0 to 53-71 % In dimethyl formamide, yields increase from 28-35% to 58-68%... 

Aluminum chloride is used in catalytic amounts and needs a promoter like water or hydrogen chloride. It is not possible to recover the catalyst because of its deactivation during the reaction. 

The acidic reagents vary widely In their ability to lower NDPA levels In trifluralin The concentration of the acid Is critical to produce the desired effect In some Instances, the acid promoted additional nitrosamine formation, e g 10% hydrochloric acid, 40% phosphoric acid, ascorbic acid, etc Hydrochloric acid and hydrogen chloride gas were the most efficient at destroying NDPA Impurity ... 

Monochlorobenzene is produced by the reaction of benzene with chlorine. A mixture of monochlorobenzene and dichlorobenzene is produced, with a small amount of trichlorobenzene. Hydrogen chloride is produced as a byproduct. Benzene is fed to the reactor in excess to promote the production of monochlorobenzene. 

The most widely applied precursors for the synthesis of monocyclic NHPs are a-diimines which can be converted to the target heterocycles either in a two-step reaction sequence involving two-electron reduction of the diimine to an enediamide, enediamine, or a-aminoamine and subsequent condensation with PC13 [18-20] or a dichlorophosphine RPC12 [21], or via direct base-promoted reaction with PC13 [20, 22], The latter reaction involves addition of a P-Cl bond to each imine moiety followed by base-promoted elimination of hydrogen chloride leading to 2,4-dichloro-... 

Aluminum chloride, used either as a stoichiometric reagent or as a catalyst with gaseous hydrogen chloride, may be used to promote silane reductions of secondary alkyl alcohols that otherwise resist reduction by the action of weaker acids.136 For example, cyclohexanol is not reduced by organosilicon hydrides in the presence of trifluoroacetic acid in dichloromethane, presumably because of the relative instability and difficult formation of the secondary cyclohexyl carbocation. By contrast, treatment of cyclohexanol with an excess of hydrogen chloride gas in the presence of a three-to-four-fold excess of triethylsilane and 1.5 equivalents of aluminum chloride in anhydrous dichloromethane produces 70% of cyclohexane and 7% of methylcyclopentane after a reaction time of 3.5 hours at... 

Hydride-promoted reactions are also well known, such as the acrylic and vinylacrylic syntheses (examples 7-10, Table VII). Some less-known compounds, which form in the presence of halide ions added to tetracar-bonylnickel, have been described by Foa and Cassar (example 11, Table VII). Reaction of allene to form methacrylates, and of propargyl chloride to give itaconic acid (via butadienoic acid), have been reported (examples 13 and 14, Table VII). 1,5-Hexadiene has been shown to be a very good substrate to obtain cyclic ketones in the presence of hydrogen chloride and tetracarbonylnickel (example 15, Table VII). The latter has also been used to form esters from olefins (example 16, Table VII). In the presence of an organic acid branched esters form regioselectivity (193). 

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