Aluminum tetrabromide

The transfer of halide from 7r-allylnickel halide to aluminum to give a haloaluminum anion results in a strong decrease in the electron density and formation of free coordination positions on nickel. The presence and number of free coordination positions can be demonstrated by reaction with carbon monoxide. The catalytically active complex, XIII, reacts at —40°C. with 2 moles of carbon monoxide to give the inactive XIV which can be isolated. In XIII, there are accordingly two free coordination positions. During catalysis, these positions are presumably occupied by olefins in the form of 7r-complexes. A stable olefin 7r-complex, 7r-allylnickel (7T-cycloocta-l,5-diene) aluminum tetrabromide, XV, can actually be isolated by adding cycloocta-l,5-diene to a solution of the active complex, XIII. 

Whenever you are drawing a proton transfer, you should show the base that is removing the proton. In this particular case, it might be tempting to use Br to remove the proton. But Br is not a good base. (In the first semester, we learned the difference between basicity and nucleophilicity, and we saw that Br is a very good nucleophile but a very poor base.) Instead, aluminum tetrabromide functions as the base that removes the proton. Notice that aluminum tetrabromide functions as a dehv-ery agenf of Br. ... 

Tungsten tetrabromide [12045-94-2] WBr, black orthorhombic crystals, is formed by the thermal-gradient reduction of WBr with aluminum, similar to the reduction of WCI4 (10). 

Zirconium tetrabromide [13777-25-8] ZrBr, is prepared direcdy from the elements or by the reaction of bromine on a mixture of zirconium oxide and carbon. It may also be made by halogen exchange between the tetrachloride and aluminum bromide. The physical properties are given in Table 7. The chemical behavior is similar to that of the tetrachloride. 

When treated with aluminum bromide at 100°C, carbon tetrachloride is converted to carbon tetrabromide [558-13-4], reaction with calcium iodide, Cal2, at 75°C gives carbon tetraiodide [507-25-5]. With concentrated hydroiodic acid at 130°C, iodoform [75-47-8], CHI, is produced. Carbon tetrachloride is unaffected by gaseous fluorine at ordinary temperatures. Replacement of its chlorine by fluorine is brought about by reaction with hydrogen fluoride at a... 

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. 

Phthalaldehyde has been made by the action of potassium hydroxide on o- (dichloromethyl)benzaldehyde,6 by the hydrolysis of a,a,a, a -tetrachlorO -xylene,6 and by the hydrolysis of the a cqe/ja -tetraacetate of o-phthalaldehyde.3 The present method is essentially that of Thiele and Gunther.7-8 Hydrolysis of the tetrabromide may also be carried out by treatment with fuming sulfuric acid followed by water.9 For small-scale preparations of o-phthalaldehyde the reduction of N,N,N, N -tetra-methylphthalamide with lithium aluminum hydride is the method of preference.10... 

Aluminum chloride induces polymerization of 1,1-dimethylsilacyclobutane but causes (66) to ring expand to th trisilacyclohexane and, remarkably, the tetrasilaadamantane (Scheme 115) (75IZV953). The polymerization of 1,3-disilacyclobutanes, variously substituted, both thermally and catalyzed has been widely studied by Russian workers. Di-/jl -chlorobis(cyclohexene)diplatinum(II) is most effective at catalyzing the polymerization of (66). The reaction is vigorous at 20-60 °C with small amounts of triethylsilane or carbon tetrabromide (Scheme 116) <66JCS(C)1137>. 

Dihydropyridazino[l,2-a]pyridazine-l,4-dione (46) is readily brominated in methylene chloride at -78 °C to give the dibromide (47) (72TL1885). The tetrabromide (48) can be formed by treatment of the starting material with two equivalents of bromine in chloroform at room temperature (75JOC47). Debromination of the dibromide (47) with l,5-diazabicyclo[4.3.0]non-5-ene in refluxing benzene yields pyridazino[l,2-a]pyridazine-1,4-dione. Debromination of the reduced tetrabromo compound (49) occurs with lithium aluminum hydride to give l,4,6,9-tetrahydropyridazino[l,2-a]pyridazine (50). 

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. 

By reduction of the ester groups with lithium aluminum hydride the corresponding tetraalcohol was obtained which was converted to the tetrabromide 46 by treatment with phosphorus tribromide. Debromination with zinc in the presence of maleic anhydride (MA) furnished the bis anhydride 47, which, after esterification and aromatization, provided the... 

ACETYLENE TETRABROMIDE (79-27-6) C2H2Br4 Decomposes above 374°F/190°C the presence of halogens and heavy metal derivatives may increase the sensitivity of this material. Reacts with alkalis, oxidizers, chemically active metals magnesium. Hot iron, aluminum, or zinc in the presence of steam may produce toxic vapors. Softens or destroys most plastics and rubbers. 

Aluminum bromide and iodide, however, have special utility in the conversion of oxides to the corresponding halides. Prigent (66) has reported that UOj heated with carbon tetrabromide at 165° forms UBr4. Uranium tetrabromide has also been prepared by reaction of uranium dioxide with a tenfold excess of carbon tetrabromide at 175° and subliming away the UBr4 formed (22). 

S,6S)-isomer (9%). Reaction of 571 with lithium aluminum hydride effected reduction of both the lactone and the N-methoxylactam, leading to the diol (—)-572. The primary alcohol was brominated by Appel reaction with carbon tetrabromide and triphenylphosphine, the bromide then cycliz-ing spontaneously to give the oft-synthesized swainsonine acetonide (-)-488 in 88% yield. Finally, hydrolysis with aqueous hydrochloric acid followed by purification by ion-exchange chromatography provided the target alkaloid, (—)-378. 

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