Alcohols exchange reactions

Alcohols (ROH) are often employed as the solvent medium for aikoxides compounds. In this situation, the alcohol also fills the role of reactant, in addition to its roles as solvent and common medium. Alcohol exchange reactions are well known in many of the more common systems that have been investigated. In simple terms, the reaction may be shown as follows ... 

The alcohol exchange reaction was shown above in equation (2). The reactive alkoxy group (OR) is replaced by an alkoxy group that has less hydrolysis sensitivity (OR ). A representative example here is the use of reagents such as zirconium n-propoxide and titanium /-propoxide, both of which possess polar bonds, for the production of lead zirconate titanate films. Commonly in these processes, R OH is 2-methoxyethanol (CH3OCH2CH2OH), which is generally present as a bidentate ligand.35... 

Scheme 12.26 Proposed mechanism for the MPV reduction catalyzed by MCM-41-supported Nd-alkoxide complexes (1 and 8A-D) (i) and (iv) alcohol exchange reactions (ii) adduct formation and (iii) acetone elimination.

U(OEt)5 is easily prepared by oxidation of U(OEt)4 by bromine in ethanol, followed by addition of the calculated quantity of sodium ethoxide, a reaction which yields181 only Np(OEt)4Br in the case of Np(OEt)4. U(OEt)s is commonly used as the starting material for the preparation of other uranium(V) alkoxides by alcohol exchange reactions. A comprehensive review of metal alkoxides includes a useful discussion of the uranium(V) compounds.182... 

An in-depth study of the industrially important hydrolysis of titanium alkoxides has been carried out by Bradley.234,235 A number of intermediate complexes were isolated and characterized. The alcohol exchange reaction has been discussed previously. The addition of hydrohalous acids to alkoxides is clearly related to the reverse reaction, the addition of alcohols to metal halides. In general, the products of these two reactions will be the same (equation 59). Hence, complete substitution will occur to give metal halides that are known to form only alcoholates with alcohols (equations 60 and 61),31,236... 

A monomeric Ce(IV)-siloxide was prepared by an alcohol exchange reaction (Eq. 6). The 6-coordination in Ce(OSiPh3)4(DME) is considered as a (4 4- 2) environment with the four siloxy oxygen atoms occupying the sites of a distorted tetrahedron [53],... 

Preparative Methods chiral titanates are usually prepared by mixing dichlorodiisopropoxytitanium and a chiral 1,4-diol in toluene. Other solvents such as ether and dichloromethane can also be employed. The alcohol exchange reaction takes place immediately at rt. Wherever necessary, liberated isopropyl alcohol is removed by azeotropic removal with toluene. The chiral 1,4-diols are prepared from dimethyl (or diethyl) tartrate by a two-step procedure comprising acetalization followed by the addition of an aryl Grignard reagent. ... 

A similar heterolytic cleavage reaction has been considered for diazoacetate esters to explain their alcoholic exchange reaction ". ... 

Another key reaction associated with the use of this solvent is the alcohol exchange reaction, which results in reduced hydrolysis sensitivity of the starting reagents, such as zirconium -propoxide and titanium i-propoxide, frequently used in the production of PZT films. This reaction is represented as Alcohol exchange... 

Other homoleptic uranium(VI) hexakisalkoxides are prepared from alcohol exchange reactions of U(0CH2CH3)6 with other alcohols (OR R = Me, Pr, Pr , Bu). ... 

Route (a) may be subdivided into two main groups the alcohol exchange reactions (Eq. 193), and reactions of metal(loid) chlorides with alcohols in the presence of a suitable chloride acceptor (Eqs. 195-197). Some of these types of reactions are illustrated by the Eqs. 193-197 ... 

In general, the equilibrium in a base-catalyzed alcohol exchange reaction lies in the direction of incorporation of the less acidic alcohol in the ester. This is a reflection both of the kinetic factor, the more acidic alcohol being a better leaving group, and the greater stabilization provided to the carbonyl group by the more electron-rich alkoxy substituent. 

Finally, alcohol exchange reactions are a means of obtaining more appropriate precursor, starting from commercial or easily accessible metal alkoxides (see Sec. II.C). 

Other examples which strongly support the existence of a metal-metal double bond are furnished by the dinuclear alkoxo-bridged dimers (10). Several synthetic procedures have been reported for the preparation of these compounds. They include the oxidation of quadruply bonded tungsten compounds in alcoholic HCl solutions, the oxidation of [W2Cl9] in alcohols, the electrolytic reduction of alcoholic solutions of WCle and the alcoholysis of WCU. Other alkoxy derivatives can be prepared by a simple alcohol exchange reaction."... 

Glycols are highly reactive towards metal alkoxides to form homoleptic and mixed alkoxo-glycolate derivatives. This alcohol exchange reaction (see Section 7.10.3.1.3) is driven by the formation of chelated or bridged structures with both (dianionic) OCR2CR2O—... 

In general, the equilibrium in a base-catalyzed alcohol exchange reaction lies in the direction of incorporating the less acidic alcohol in the ester. 

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