Aluminium reaction with halogens

Also, psudo-P-D-mannopyranose (115) has been synthesized from 99 by the following reactions [28], Halogenation of 99 with triphenylphosphine, imidazole and iodine gave 1 L-4-0-benzyl-3-deoxy-3-iodo-1,2 5,6-di-0-isopropylidene-a//o-inositol (106), m.p. 77.4 °C, [oc]p° —30.1° (chloroform). Treatment of 106 with lithium aluminium hydride-resulted in a formation of two endocyclic olefins (107) and (108) in an approximately 1 2 ratio. Oxidation of 108with dimethyl sulfoxide and oxalyl chloride gave the enone (109) as a syrup, [a] 0 —68.11° (chloroform). Stereoselective... 

Chemical drying of liquids often involves reaction, with or without heating, of a solid which will react selectively with water. Calcium or lithium aluminium hydrides are often used evolved hydrogen needs safe venting. For the lithal, careful stirring and temperature control is essential to prevent formation of extremely reactive aluminium, which may react violently with oxygenated or halogenated solvents like dioxan or trichloroethane. 

From Aliphatic Acids.—By the introduction of an aryl radical into an aliphatic acid we may obtain side-chain carboxy acids in which the side chain is the same as in the aliphatic acid. This reaction is effected by the Friedel-Craft reagent, aluminium chloride, with the aromatic hydrocarbon together with a halogen aliphatic acid. 

Reactions of A1 with halogens at room temperature or with N2 on heating give the Al(lll) halides or nitride. Aluminium is often used to reduce metal oxides, e.g. in the thermite process (equation 12.5) which is highly exothermic. 

More evidence has appeared showing that the olefin metathesis reaction can tolerate the presence of functional groups. The catalytic system Re207-Al203, promoted by a small amount of tetramethyltin, effects metathesis of olefins in fair yield (17—40%) in the presence of unsaturated ethers and ketones, alkenyl esters, and halogeno-alkenes. The reaction is performed in carbon tetrachloride as solvent at room temperature over 6 h. Electro-reduction of tungsten hexa-chloride with an aluminium anode in halogenated solvents appears to form a complex suitable for a clean metathesis, exemplified by the conversion of pent-2-ene into its equilibrium mixture with but-2-ene and hex-3-ene. ... 

Acetophenone.—The Fnedel-Crafts reaction, of which this pieparation is a type, consists in the use of anhydious aluminium chlonde for effecting combination between an aromatic hydrocarbon or its deiivative on the one hand, and a halogen i,Cl 01 Bi) compound on the othei. The leaction 13 always accompanied by the evolution of hydiochloiic or hydio-bromic acid, and the product is a compound with AlCl-j, which decomposes and yields the new substance on the addition of watei. This reaction has been utilised, as in the present case, (r) for the prepaiation of ketones, in which an acid chloiide (aliphatic or aromatic) is employed,... 

Bromochloromethane was being prepared in a 400 1 reactor by addition of liquid bromine to dichloromethane in presence of aluminium powder (which would form some aluminium bromide to catalyse the halogen exchange reaction). The reaction was started and run for 1.5 h, stopped for 8 h, then restarted with addition of bromine at double the usual rate for 2.5 h, though the reaction did not appear to be proceeding. Soon afterwards a thermal runaway occurred, shattering the glass components of the reactor. 

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