Metal ethoxides

Table 4 Hsts the manufacturers of some metal alkoxides, and the individual materials are described in the following. Some other properties of metal ethoxides are summarized in Table 1.

The chemistry of ethyl alcohol is largely that of the hydroxyl group, namely, reactions of dehydration, dehydrogenation, oxidation, and esterification. The hydrogen atom of the hydroxyl group can be replaced by an active metal, such as sodium, potassium, and calcium, to form a metal ethoxide (ethylate) with the evolution of hydrogen gas (see Alkoxides, metal). 

Alkaline earth (Ba, Sr) metal ethoxides have been found to be more reactive than free ethoxide in the ethanolysis of simple activated amides such as A-methyl-2,2,2-trifluoroacetanilide (140), A-methyl-1-chloroacetanilide (141) and m-nitro-A-methyl-2,2,2-trifluoroacetanilide (142) enhanced catalysis was observed upon addition of equimolar amounts of 18-crown-6. ... 

It is unknown whether and to what an extent the metal-ethoxide species contains a bromide counterion, but its kinetic behavior is that of a single species. Quite remarkably, cleavage of phenyl acetate is 62 and 45 times faster with EtOSrBr and EtOBaBr, respectively, than with EtONMe4 [6]. The corresponding figures in the cleavage of p-nitrophenyl acetate are 8.0 and 7.0, respectively [5]. 

Accordingly, the simplest mechanism that accounts for the enhanced ethanolysis rates in the presence of metal ions is shown in IV, where a metal-bound ethanol molecule, made acidic by metal coordination, serves as a general acid catalyst for C—N bond cleavage. Here again enhanced reactivity is exhibited by the 18C6-complexed metal ethoxide species [13]. 

The 1-2-3 ceramic superconductor YBa2Cu307 has been synthesized by the sol-gel method from a stoichiometric mixture of yttrium ethoxide, barium ethoxide, and cop-per(II) ethoxide in an appropriate organic solvent. The oxide product, before being heated in oxygen, has the formula YBa2Cu3065. Write a balanced equation for the hydrolysis of the stoichiometric mixture of metal ethoxides. 

First, determine the chemical formulas of the metal ethoxides, and then write a balanced equation for the reaction of the mixture of metal ethoxides with water. 

The effect of cation-complexing agents on the barium(II)-assisted basic ethanolysis of phenyl acetate has been looked at.184 Addition of various crown ethers yields ternary complexes of 1 1 1 crown-metal-ethoxide composition and a definite cation activation takes place. Cryptand 222 removes the catalytic activity. 

Reaction of the metal ethoxide [M(OEt)2(HOEt)4] with the desired /3-diketone has been used as an anhydrous method to Group 2 /3-diketonates and mixed ligand/3-diketonate-alkoxide compounds. Presumably, the liberated HOR has a lower binding ability compared to liberated H20. Drake et al. have prepared [Sr3(tmhd)6(Htmhd)] and [Ba4(tmhd)8] by the reaction of Eq. (19).177 Equation (20) gives the generalized reaction for formation of mixed ligand compounds of formula [M(X)n(OR)2 ]) .184185... 

Equilibrium concentrations of semi-stabilized benzylidene ylides derived from optically pure arsonium salts and alkali metal ethoxides react with aromatic aldehydes to produce high yields of enantiomerically enriched tra s-2,3-diaryloxiranes and optically pure tertiary arsines with retention of configuration at arsenic (equation S)" -" . 

In P-CH elimination on d -metal ethoxide complexes, the orbital interactions have to take place in such a manner that the electron donation from cr(CH) to o (MO) and the back-donation from sigma (M) to ct (CH) are required to form the MH o and CO n bonds and... 

A direct procedure, partly based in earlier knowledge, giving the chrom-3-ene (2H-benzo[b]pyran) structure in one-step has been referred to earlier. In this method titanium or magnesium phenolates formed from the phenol with the metal ethoxide and removal of ethanol, are then reacted with a,p-unsaturated aldehydes or ketones in toluene solution at 110 C over 8 hours (ref. 40). In this way precocene 2 was derived from the reaction of the magnesium salt of... 

The rates of transesteriflcation in anhydrous EtOH at 298 K of 4-nitrophenyl picolinate (12), nicotinate (13), and isonicotinate (14) in the presence of alkali metal ethoxides (EtOM M = K, Na, Li) were compared. Rates were greatest for 4-nitrophenyl picolinate (12) for each alkali metal, and the fastest rate was observed for EtONa. This was attributed to the formation of a flve-membered cyclic transition state (15), of optimal stability for M = Na, which is not possible for (13) or (14). 

Table 2.18 Assignment of M-O and C-O stretching frequencies in metal ethoxides, [M(OEt),] ...

Clearly the notion of ion pairs is well established (Szwarc, 1968,1972). In any but very polar solvents, it should therefore be assumed that ions invoked in mechanisms may exist partly or chiefly as pairs, which will have an effect on the form of the rate law for a reaction (see Problem 2.2). Szwarc (1972, p. v) emphasizes the importance of ion pairing in mechanisms. The presence or absence of ion pairing may lead to very different rates, or even different courses of reaction. In a study by Dunn and Buncel (1989) of the ethanolysis of p-nitrophenyldiphenyl phosphinate (5), the kinetic behavior of different alkali metal ethoxides indicated that EtO M ion pairs are more reactive than the free EtO" ions. 

Ethanol burns in air with a blue flame, forming carbon dioxide and water. It reacts with active metals to form the metal ethoxide and hydrogen, e.g., with sodium it forms sodium ethoxide. It reacts with certain acids to form esters, e.g., with acetic acid it forms ethyl acetate. It can be oxidized to form acetic acid and acetaldehyde. It can be dehydrated to form diethyl ether or, at higher temperatures, ethylene. 

A kinetic study of the nucleophilic substitution of Y-phenyl diphenylphosphinoth-ioates (125 X = S) by alkali metal ethoxides (MOEt M = Li, Na, K) in anhydrous ethanol at 298 K was reported (Scheme 39). Plots of pseudo-first-order rate constants ( obsd) versus [MOEt] showed distinct upwards (KOEt) and downwards (LiOEt) curvatures, respectively, pointing to the importance of ion-pairing phenomena and a differential reactivity of dissociated EtO and ion-paired MOEt. The reactivity of MOEt towards the 4-nitro compound (125 X = S, Y = 4-N02> increases in the order LiOEt < EtO < NaOEt < KOEt, which differs from the reactivity order LiOEt > NaOEt > KOEt > EtO reported previously for the reaction of 4-nitrophenyl diphenylphosphinate (125 X = O, Y = 4-NO2). Yukawa-Tsuno analysis revealed that the reactions of (125 X = S) and its P=0 analogue (125 X=O) with MOEt proceeded through the same concerted mechanism, which involved M+ ions increasing the electrophilicity of the reaction centre via TS (126). The P=0 compounds (125 X = O) were approximately 80-fold more reactive towards the dissociated EtO than the P=S compounds (125 X = S) (regardless of the electronic nature of substituent Y) but were up to 3100-fold more reactive towards ion-paired LiOEt. ... 

A kinetic study of the nucleophilic substitution reaction of substituted phenyl diphenylphosphinates (530a) and diphenylphosphinothioates (530b) with alkali-metal ethoxides (MOEt M = Li, Na, K) in anhydrous ethanol has been reported (Scheme 178). Experimental studies revealed the wide-ranging and important effects of structural change P=0 to P=S bond on reactivity, mechanisms (concerted versus stepwise), and on... 

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