Metal alkoxides carbon-hydrogen

The reactions are usually carried out by adding the halo ketone to a solution or suspension of the base in either a protic solvent (water, alcohols) or an ether (diethyl ether, dioxane, dimethoxyethane). The bases employed include hydroxides of Group I and Group II metals alkoxides, carbonates and hydrogen-carbonates of Group I metals ammonia, and amines. There is no one recommended set of experimental conditions, because both the mechanism of the reactions and the type of products obtained depend upon the initial choice of a-halo ketones. In addition, since the halo ketones are highly reactive molecules, side products are inevitably obtained those most commonly produced are shown in Scheme... 

Alkaline earth metal alkoxides decompose to carbonates, olefins, hydrogen, and methane calcium alkoxides give ketones (65). For aluminum alkoxides, thermal stability decreases as follows primary > secondary > tertiary the respective decomposition temperatures are ca 320°C, 250°C, and 140°C. Decomposition products are ethers, alcohols, and olefins. 

Meerwein-Ponndorf-Verley-Type Reduction Reduction of ketones by 2-propanol or related alcohols, known as Meerwein-Ponndorf-Verley (MPV) reduction, is promoted by various metal alkoxides, typically aluminum 2-propoxide [2a,d,281]. The C2 hydrogen of 2-propanol is transferred directly to the carbonyl carbon through a six-membered pericyclic transition state [284], Earlier, a stoichiometric quantity of a metal alkoxide was required for this purpose, but recently, lanthanide [285] and aluminum [286] complexes acting as excellent catalysts have been reported. 

The initial step of the process is the formation of aluminum triethyl from aluminum metal, ethylene and hydrogen. In a second step ethylene is added to the aluminum triethyl causing the carbon chains to grow in increments of two carbon atoms. After the chain growth reaction the aluminum alkyl is oxidized to an aluminum alkoxide. The alkoxide is then hydrolyzed with water, forming fatty alcohols and alumina slurry. The alcohols and the alumina slurry can be separated from each other and processed into the final products. After drying of the slurry the alumina is obtained in the form of a high purity aluminum oxide monohydrate of boehmite or pseudoboehmite structure. 

The alkylation of substances such as )8-diketones, j8-ketoesters, and esters of malonic acid can be carried out in alcoholic solvents using metal alkoxides as bases. The presence of two electron-withdrawing substituents favors formation of a single enolate by abstraction of a hydrogen from the carbon situated between them. Alkylation then occurs by an Sn2 process. 

The key step in the metal hydride reduction of an aldehyde or a ketone is the transfer of a hydride ion from the reducing agent to the carbonyl carbon to form a tetrahedral carbonyl addition intermediate. In the reduction of an aldehyde or a ketone to an alcohol, only the hydrogen atom attached to carbon comes from the hydride-reducing agent the hydrogen atom bonded to oxygen comes from the water added to hydrolyze the metal alkoxide salt. 

Some reactions of trimethylchlorosilane are summarized in Fig. 4.4. Many of these involve nucleophilic attack at silicon in which chlorine is substituted by another group. Alkoxysilanes are obtained using metal alkoxides or alcohols in the presence of pyridine. If the latter reaction is carried out in a non-polar solvent such as light petroleum, pyridinium hydrochloride is precipitated and may be filtered off, leaving the alkoxysilane in solution. Hydrogen chloride cleaves carbon-oxygen bonds in alkoxysilanes (as it does in ethers also) to form an alkyl halide and a siloxane ... 

On the alcohol product, the hydrogen atom bonded to carbon comes from the hydride reducing agent and the hydrogen atom bonded to oxygen comes from water during hydrolysis of the metal alkoxide salt. 

In the absence of hydrogen, a catalytic reaction of carbon monoxide and an alcohol produces alkyl formate (Eq. 7.7). The catalyst involved is an alkali metal alkoxide alone or together with a transition metal carbonyl cluster, e.g. Ru3(CO)i2. ° ... 

The details of the mechanism are poorly understood, though the oxygen of the alcohol is certainly attacking the carbon of the isocyanate. Hydrogen bonding complicates the kinetic picture. The addition of ROH to isocyanates can also be catalyzed by metallic compounds, by light, or, for tertiary ROH, by lithium alkoxides ° or n-butyllithium. ° ... 

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