Aluminum bromide catalyst

C (8) and n-butane-l-C (9) were contacted in the presence of aluminum bromide promoted with water. In the study however, of the liquid-phase isomerization of 2-methylbutane-l-C over an aluminum bromide catalyst... 

The complex resulting from the action of water on aluminum bromide, freed from any noncombined hydrogen bromide, was used as a catalyst for the isomerization of n-butane. It was found that by contacting n-butane at 25 for 20 hours with the catalysts, isomerization occurred when the molal ratio of water-aluminum bromide was 1, 2, or 3 (Table IX, B). When the ratio was 4, slight isomerization occurred at 25°, but appreciably more occurred at 80°. With a ratio of 6, no isomerization occurred. No appreciable evolution of hydrogen bromide was noticed in these experiments. The results obtained demonstrate that the isomerizing catalyst formed by the action of water on aluminum bromide is not equivalent to an aluminum bromide catalyst, inasmuch as the latter requires hydrogen bromide and traces of olefins to cause the isomerization of n-butane. 

It was found that by treating either n-butane or isobutane with 10 mole % deuterium bromide-aluminum bromide catalyst for 20 hours at 25°, no isomerization of the butanes occurred and only 6 and 9.5% of the deuterium exchanged with n-butane and isobutane, respectively. When, however, 0.1 mole % butenes was added to n-butane and the isomerization reaction was carried out under the same experimental conditions, over 40% of the butane isomerized to isobutane and 92% of the deuterium underwent an exchange reaction. These results indicate clearly that olefins take an active part in isomerization. The results obtained are in agreement with the proposed mechanism of isomerization. 

Ben2enesulfonic anhydride has been claimed to be superior to ben2enesulfonyl chloride (140). Catalysts used besides aluminum chloride are ferric chloride, antimony pentachloride, aluminum bromide, and boron trifluoride (141). 

Aluminum bromide and chloride are equally active catalysts, whereas boron trifluoride is considerably less active probably because of its limited solubiUty in aromatic hydrocarbons. The perchloryl aromatics are interesting compounds but must be handled with care because of their explosive nature and sensitivity to mechanical shock and local overheating. 

Boron tribromide [10294-33A], BBr, is used in the manufacture of diborane and in the production of ultra high purity boron (see Boron, ELEMENTAL BoRON COMPOUNDS). Anhydrous aluminum bromide [7727-15-3], AIBr., is used as an acid catalyst in organic syntheses where it is more reactive and more soluble in organic solvents than AlCl. Tballium bromide [7789AOA], TlBr, is claimed as a component in radiographic image conversion panels (39). 

At 225—275°C, bromination of the vapor yields bromochloromethanes CCl Br, CCl2Br2, and CClBr. Chloroform reacts with aluminum bromide to form bromoform, CHBr. Chloroform cannot be direcdy fluorinated with elementary flourine fluoroform, CHF, is produced from chloroform by reaction with hydrogen fluoride in the presence of a metallic fluoride catalyst (8). It is also a coproduct of monochlorodifluoromethane from the HF—CHCl reaction over antimony chlorofluoride. Iodine gives a characteristic purple solution in chloroform but does not react even at the boiling point. Iodoform, CHI, may be produced from chloroform by reaction with ethyl iodide in the presence of aluminum chloride however, this is not the route normally used for its preparation. 

Photochlorination of tetrachloroethylene, observed by Faraday, yields hexachloroethane [67-72-1]. Reaction with aluminum bromide at 100°C forms a mixture of bromotrichloroethane and dibromodichloroethane [75-81-0] (6). Reaction with bromine results in an equiUbrium mixture of tetrabromoethylene [79-28-7] and tetrachloroethylene. Tetrachloroethylene reacts with a mixture of hydrogen fluoride and chlorine at 225—400°C in the presence of zirconium fluoride catalyst to yield l,2,2-trichloro-l,l,2-trifluoroethane [76-13-1] (CFG 113) (7). 

There are relatively few kinetic data on the Friedel-Crafts reaction. Alkylation of benzene or toluene with methyl bromide or ethyl bromide with gallium bromide as catalyst is first-order in each reactant and in catalyst. With aluminum bromide as catalyst, the rate of reaction changes with time, apparently because of heterogeneity of the reaction mixture. The initial rate data fit the kinetic expression ... 

An obvious method to investigate the formation and the nature of the catalytically active nickel species is to study the nature of products formed in the reaction of complexes such as 3 or 4 with substrate olefins. This has been investigated in some detail in the case of the catalytic dimerization of cyclooctene to 1-cyclooctylcyclooctene (17) and dicy-clooctylidene (18) [Eq. (4)] using as catalyst 7r-allylnickel acetylacetonate (11) or 7r-allylnickel bromide (1) activated by ethylaluminum sesquihalide or aluminum bromide (4). In a typical experiment, 11 in chlorobenzene was activated with excess ethylaluminum sesquichloride cyclooctene was then added at 0°C and the catalytic reaction followed by removing... 

Treatment of 19 with ethy(aluminum sesquichloride or aluminum bromide results in the formation of a new catalyst, which is active for the dimerization of olefins such as ethylene or propene but inactive for the dimerization of cyclooctene. 

The metal halide catalysts include aluminum chloride, aluminum bromide, ferric chloride, zinc chloride, stannic chloride, titanium tetrachloride and other halides of the group known as the Friedel-Crafts catalysts. Boron fluoride, a nonmetal halide, has an activity similar to that of aluminum chloride. 

The catalytic activity of certain of the Friedel-Crafts catalysts was shown to decrease over a very wide range in the series boron fluoride, aluminum bromide, titanium tetrachloride, titanium tetrabromide, boron chloride, boron bromide and stannic chloride (Fairbrother and Seymour, mentioned in Plesch al., 83). When boron fluoride is added to isobutylene at dry ice temperatures, the olefin is converted to a solid polymer within a very few seconds. The time required for complete polymerization with aluminum bromide hardly extends to a few minutes while reaction times of hours are required with titanium chloride and periods of days with stannic chloride. 

Reactions, e.g., with alkyl halides in ether using Ziegler-Natta catalyst form alkyl aluminum halides, R3AI2X3, [R2A1X]2 and [RA1X]2 with bromine vapor forms anhydrous aluminum bromide,... 

Halans has studied the aluminum bromide catalyzed decomposition of phenyl azide in toluene solution at 0° in the presence of traces of hydrogen bromide.1 He has found that an equimolecular complex is formed between the catalyst and phenyl azide and that the catalyst is consumed in the reaction. On the basis of kinetic results, Scheme VI has been proposed for the decomposition mechanism. In connection herewith, Halans observed that whereas an equimolecular mixture of phenyl azide and hydrogen bromide does not decompose at 0°, a mixture of phenyl azide, aluminum bromide, and hydrogen bromide in the ratio 1/1/1 decomposes instantaneously at 0°. 

Disulfides were shown to be intermediates in the iodine oxidation of 1,3-butadiene-l-thiols and related compounds to form thiophenes (56JOC39). Several simple disulfides were converted to thiophene derivatives under these same conditions (64JOC2372). For example, bis(2-biphenyl) disulfide (13) produced dibenzothiophene (14) in 64% yield when heated with iodine in ethylene glycol for one hour. Treatment of (13) in benzene with aluminum bromide gave (14) in 76% theoretical yield, with an equivalent amount of the thiol, 2-biphenylthiol (62JOC4111). Thus the iodine reagent is more efficient, since it oxidizes the mercaptan, formed by the Friedel-Crafts reaction of disulfide on the adjacent aromatic ring, to disulfide for further reaction, and also serves as a catalyst for the initial reaction. 

In their review, Natta and co-workers (6) were able to show that the highest content of crystalline polyvinylisobutylether was obtained with diethylaluminum chloride and ethylaluminum dichloride, and lesser amounts with aluminum bromide. Triethylaluminum was ineffective as a catalyst. 

Styrene and alphamethylstyrene have been polymerized with a number of different catalyts. Phillips, Hanlon and Tobolsky (38) found that low-styrene content copolymers are obtained with cationic Friedel-Crafts type catalysts while high styrene containing copolymers are obtained with anionic catalysts. Aluminum bromide or BFS etherate... 

Karapinka, Smith, Carrick (79) studied the use of methyltitanium trichloride as a catalyst for polyethylene. Alone it was inactive for the polymerization of polyethylene. It required the predecomposition to titanium trichloride at 120° or the addition of titanium trichloride to produce an active catalyst. Vanadium tetrachloride also produced an active catalyst. Aluminum bromide failed to activate the catalyst, whereas trialkylaluminum which reacts to produce alkylaluminum chlorides was effective. 

Aluminum bromide AlBr3 is used as a catalyst and parallels AICI3 in this role. Strontium and magnesium bromides are used to a limited extent m phamiacentical applications. Ammonium bromide is nsed as a flame retardant in some paper and textile applications potassium bromide is used in photography. Phosphorus tribromidc PBr3 and silicon tetrabromide SiBi4 are nsed as intermediates and catalysts, notably in the production of phosphite esters. 

The aluminum bromide functions in the addition of bromine to tetrachloroethene as a catalyst, which is something that facilitates the conversion of reactants to products. The study of the nature and uses of catalysts will concern us throughout this book. Catalysis is our principal means of controlling organic reactions to help form the product we want in the shortest possible time. 

The redistribution reaction in lead compounds is straightforward and there are no appreciable side reactions. It is normally carried out commercially in the liquid phase at substantially room temperature. However, a catalyst is required to effect the reaction with lead compounds. A number of catalysts have been patented, but the exact procedure as practiced commercially has never been revealed. Among the effective catalysts are activated alumina and other activated metal oxides, triethyllead chloride, triethyllead iodide, phosphorus trichloride, arsenic trichloride, bismuth trichloride, iron(III)chloride, zirconium(IV)-chloride, tin(IV)chloride, zinc chloride, zinc fluoride, mercury(II)chloride, boron trifluoride, aluminum chloride, aluminum bromide, dimethyl-aluminum chloride, and platinum(IV)chloride 43,70-72,79,80,97,117, 131,31s) A separate catalyst compound is not required for the exchange between R.jPb and R3PbX compounds however, this type of uncatalyzed exchange is rather slow. Again, the products are practically a random mixture. 

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