Ethoxide, aluminum

Ethyl acetate [141-78-6] is produced commercially by the Tischenko condensation of acetaldehyde using an aluminum ethoxide catalyst (60). The Tischenko reaction of acetaldehyde with isobutyraldehyde [78-84-2] yields a mixture of ethyl acetate, isobutyl acetate [110-19-0] and isobutyl isobutyrate [97-85-8] (61). 

Upon treatment with aluminum ethoxide, the aldehyde is converted to cinnamyl cinnamate [122-69-0] (Tishchenko reaction), a valuable perfumery ingredient. 

Reaction between aldehydes and aluminum ethoxide (Tishchenko)... 

Aluminum ethoxide, 21, 9 Aluminum isopropoxide, 21, 9 Amalgamated zinc, 20, 57 23, 86 Amide, 20, 37, 62, 66 preparation by ammonolysis, 20, 62 Amination, by reduction of a ketone in the presence of ammonia, 23, 68 of bromoacetal with use of high-pressure hydrogenation bomb, 24, 3 of a-bromoisocaproic acid, 21, 75 of a -bromo-/3-methylvaleric acid, 21, 62... 

When aldehydes, with or without a hydrogen, are treated with aluminum ethoxide, one molecule is oxidized and another reduced, as in 9-69, but here they are found as the ester. The process is called the Tishchenko reaction. Crossed Tishchenko reactions are also possible. With more strongly basic alkoxides, such as magnesium or sodium alkoxides, aldehydes with an a hydrogen give the aldol reaction. Like 9-69, this reaction has a mechanism that involves hydride transfer.751 The Tishchenko reaction can also be catalyzed752 by ruthenium complexes.753 by boric acid,754 and, for aromatic aldehydes, by disodium tetracarbonylferrate Na2Fe(CO)4,755 OS I, 104. 

Oxidation of enol ethers 9-70 Reaction between aldehydes and aluminum ethoxide (Tishchenko) 9-72 Reaction of acetophenones with AgN03-I2 or other reagents... 

Aluminum fer/.-butoxide can be prepared by refluxing dry tert. -butyl alcohol with amalgamated aluminum 5l 6 or aluminum plus mercuric chloride.6 The method described is that of Adkins and Cox.0 The preparation of amalgamated aluminum has been described.3, 4 Aluminum isopropoxide can be prepared from dry isopropyl alcohol and aluminum,1 2 the method being essentially that described for aluminum ethoxide (Org. Syn. is, 82). 

Alumina (A1203) powders can be prepared from aluminum ethoxide by the sol-gel method. Write a balanced equation for the hydrolysis of aluminum ethoxide. 

First, determine the chemical formula of aluminum ethoxide, and then write a balanced equation for the reaction of aluminum ethoxide with water. 

Because aluminum is a group 3A element, it has an oxidation number of +3. The ethoxide ligand is the anion of ethanol, HOCH2CH3, and has a charge of —1. Since aluminum ethoxide is a neutral compound, its formula must be Al(OCH2CH3)3. The hydrolysis reaction, which breaks the Al-OCH2CH3 bonds and forms Al-OH bonds, requires one H20 molecule for each ethoxide ligand ... 

In 1925 it was discovered independently by Verley1 and by Meerwein and Schmidt that an aldehyde can be reduced to the primary alcohol by treatment with aluminum ethoxide in the presence of ethanol The reduction of the aldehyde occurs at the expense of an equivalent amount of ethanol which is oxidized to acetaldehyde. 

The reaction is reversible, but the equilibrium can be shifted to the point of complete reduction by removal of the acetaldehyde with a stream of dry hydrogen or nitrogen. This has the additional advantage of preventing side reactions such as an aldol condensation between the original aldehyde and acetaldehyde. The method of reduction with aluminum ethoxide was found applicable to several aldehydes but to only a few ketones of special types. 

Further Reduction to a Hydrocarbon. In the reduction of benzo-phenone with aluminum ethoxide the formation of 7% of diphenyl-methane was observed. When benzohydrol was treated with aluminum ethoxide under the same conditions, 28% reduction to diphenylmethane occurred.12 In these reactions acetic acid, rather than acetaldehyde,-was formed from the ethoxide. Aluminum isopropoxide does not give this type of undesirable reaction with this reagent, pure benzohydrol is easily obtained in 100% yield from benzophenone.6 37 However, one case of reduction of a ketone to the hydrocarbon has been observed with aluminum isopropoxide.17 When 9, 9-dimethylanthrone-10 (XU) was reduced in xylene solution, rather than in isopropyl alcohol, to avoid formation of the ether (see p. 190), the hydrocarbon XUII was formed in 65% yield. The reduction in either xylene or isopropyl alcohol was very slow, requiring two days for completion. 

For the reduction of aldehydes, anhydrous isopropyl alcohol is recommended as the solvent in order to avoid side reactions such as the Tishchenko reaction.13 In those reductions for which aluminum ethox-ide is satisfactory either ethyl or isopropyl alcohol may be employed as a solvent. For most aldehydes, the temperature of boiling isopropyl alcohol is satisfactory for rapid and complete reduction. Certain sensitive aldehydes or ketones may be reduced at room temperature by letting the mixture stand for several days. When aldehydes are reduced, a slow stream of dry nitrogen or hydrogen is frequently employed for reactions requiring long periods of time (including most of the aluminum ethoxide reductions), or when the reduction products are sensitive to air. 

A procedure for the use of aluminum ethoxide in the reduction of chloral is described by Chalmers in Organic Syntheses,16... 

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