Carboxylate anions acetate

A few mixed compounds of Eu3+ containing dibenzoylmethide ion and carboxylate anions (acetate, propionate and benzoate) of the general formula, (DBM)2EuOCOR, have been isolated [43Z], Thermogravimetric investigations on these complexes show that their heat stability decreases in the order acetate > propionate > benzoate. The melting points of... 

Molecules 20-22 in which a ferrocene-lj -bisamide is bridged across the upper rim of a calix[4]arene show interesting anion sensing selectivity [19]. The results of H NMR studies in CD3CN show that the receptors preferentially bind carboxylate anions (acetate and benzoate) over dihydrogenphosphate and chloride. 

This difference in behavior for acetic acid in pure water versus water buffered at pH = 7 0 has some important practical consequences Biochemists usually do not talk about acetic acid (or lactic acid or salicylic acid etc) They talk about acetate (and lac tate and salicylate) Why Its because biochemists are concerned with carboxylic acids as they exist in di lute aqueous solution at what is called biological pH Biological fluids are naturally buffered The pH of blood for example is maintained at 7 2 and at this pH carboxylic acids are almost entirely converted to their carboxylate anions... 

Bonhote and co-workers [10] reported that ILs containing triflate, perfluorocar-boxylate, and bistrifylimide anions were miscible with liquids of medium to high dielectric constant (e), including short-chain alcohols, ketones, dichloromethane, and THF, while being immiscible with low dielectric constant materials such as alkanes, dioxane, toluene, and diethyl ether. It was noted that ethyl acetate (e = 6.04) is miscible with the less-polar bistrifylimide and triflate ILs, and only partially miscible with more polar ILs containing carboxylate anions. Brennecke [15] has described miscibility measurements for a series of organic solvents with ILs with complementary results based on bulk properties. 

What is true for acetic acid is also true for other carboxylic acids at the ph ysiological pH that exists inside cells, carboxylic acids are almost entirely dissociated. To reflect this fact, we always refer to cellular carboxylic acids by the name of their anion—acetate, lactate, citrate, and so forth, rather than acetic acid, lactic acid, and citric acid. 

Because the dissociation of a carboxylic acid is an equilibrium process, any factor that stabilizes the carboxylate anion relative to undissociated carboxylic acid will drive the equilibrium toward increased dissociation and result in increased acidity. An electron-withdrawing chlorine atom, for instance, makes chloroacetic acid (Ka = 1.4 x 10-3) approximately 80 times as strong as acetic acid introduction of two chlorines makes dichloroacetic acid 3000 times as strong as acetic acid, and introduction of three chlorines makes trichloroacetic acid more than 12,000 times as strong. 

Figure I indicates the approach used to synthesize poly(oxyethylene)-b-poly(pivalolactone) telechelomers. An acetal capped anionic initiator, X (13) polymerizes ethylene oxide (EO) to give 2> a potassium alkoxide of a masked polyether, and this "new" initiator is to be used to polymerize pivalolactone (PVL). Since potassium alkoxides are strong nucleophiles, they can randomly attack at both the carbonyl carbon and the 3-methylene carbon in lactones, (Figure 2) such a random attack would result in a pivalolactone segment containing irregularities. Lenz (15), and Hall (16), and Beaman (17) have investigated PVL polymerization and have shown that the less nucleophilic carboxylate anion is preferable in polymerizing PVL smoothly. The weaker carboxylate anion will attack only at the methylene...

Although the reaction could proceed via intermediate 14 or 15, the authors favour a mechanism where the formation of 14 is rate-determining because the displacement of the acetate at Pb by carboxylate anions is known to be rapid. The large negative AS (—34 e.u./mol) observed for the oxidation reaction is consistent with formation of the pseudo-cyclic intermediate 14. Also, the small Hammett p value of 0.4 determined for a series of meta- and para-substituted mandelic acids indicates that there is very little charge development on the benzyl carbon in the transition state of the rate-determining step. This is also consistent with the proposed mechanism. 

In the case of benzal chloride, the carboxylation in conventional diaphragm systems fails, leading to poor yields in phenylacetic and mandelic add [180], At an Al anode, carboxylation occurs because the self-esterification of the first carboxylate anion onto the second chloride group is hindered by the formation of Al complex salts [181]. Yields of phenylmalonic and chlorophenylic acetic acids up to 30% each have been obtained [178],... 

Fersht and Kirby, 1968b. Formation of the anhydride is rate determining here. The reference reaction is that of phenyl acetate with a carboxylate anion of pK, 3.11 (see note a) y Kemp and Thibault, 1968. The reference reaction is that of RCOO- with phenyl benzoate (see note j)... 

Capon et al. considered three possible mechanisms [equation (47)] for hydrolysis of o-methoxymethoxybenzoic acid. Mechanisms (a) and (b) involve nucleophilic attack by the carboxylate anion on the protonated acetal, and mechanism (c) proceeds with intramolecular gener2il acid catalysis. Capon was able to rule out mechanisms (a) and (b) since the synthetically prepared intermediate in (a) is stable under the reaction conditions. That in (b) leads to products at... 

The monoanionic species is most reactive, but its associated rate constant for intramolecular general acid catalysis is only 65 times greater than that for the unionized species. Most of the large rate enhancement in comparison with the dimethyl ester is due to participation by one carboxyl group, as is the case with the unionized acetal [77]. If the carboxylate anion of the monoanionic species is electrostatically stabilizing the incipient carbonium ion in the reaction [8], its effect on the rate must be small. 

Acetic acid is a representative carboxylic acid, which has the general formula RC02H, where R is an organic substituent. Most carboxylic acids are weak acids, and most carboxylate anions are weak bases. 

Esters are formed in nucleophilic substitution reactions in which the nucleophile is a carboxylate anion. The anions of carboxylic acids are relatively weak nucleophiles towards sp3-hybridized carbon. Swain s nucleophilic constant, n, for acetate ion is 2.7183, slightly smaller than that for chloride. Thus acetate is selectively alkylated by alkyl halides in aqueous solution, e.g. 

Nickel(II) complexes with simple carboxylate anions have been well known for a long time,1715 and nickel(II) acetate tetrahydrate is one of the most thoroughly studied compounds. Selected examples of nickel(II) complexes with carboxylate anions are shown in Table 85. The carboxylato complexes are high-spin octahedral with few exceptions. 

Carboxylic acids (acetic, halo substituted acetic and benzoic adds, HA) have been shown75 to interact with V-phenylbenzohydroxamates of copper(II), nickel(II) and cobalt(II) with the formation of adducts with the formula M(LL)2(HA)2 (where LL is the anion of hydroxamic acid). 

The alcoholysis reaction was found to be first order in both the silane and the catalysts, and of intermediate order in the alcohol, when catalyzed by carboxylic acids. When catalyzed by dichloro-acetic acid, the reaction has a Hammet p value of +0.43. This is consistent with a concerted displacement reaction between the alkoxysilane and the complex involving the alcohol and the carboxylate anion. The intermediate is a negatively charged intermediate, probably a penta-substituted silicon species. 

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