Ethanoate anion

It cannot be too firmly emphasised, however, that the ethanoate anion does not have two possible, and alternative, structures which are rapidly interconvertible, but a single, real structure (19ab)—sometimes referred to as a hybrid—for which the classical (canonical) structures (19a) and (19b) are less exact, limiting approximations. 

Worked Example 4.10 Consider the dissociation of ethanoic (acetic) acid in water to form a solvated proton and a solvated ethanoate anion, CH3COOH + H20 CH3COO ... 

The reaction in Equation (6.12) illustrates the coexistence of two acids and two bases. We say the ethanoate ion and ethanoic acid represent a conjugate pair, and the solvated proton and the water form a second conjugate pair. Within the ethanoic-ethanoate pair, the ethanoic acid is the conjugate acid and the ethanoate anion is the conjugate base. Similarly, H30+ is a conjugate acid to the... 

Statistically, we find fewer ethanoate anions than trichloroethanoate anions in the respective solutions of the two acids. And if there are fewer ethanoate anions in solution per mole of ethanoic acid, then there will be fewer solvated protons. In other words, the extent to which ethanoic acid dissociates is less than the corresponding extent for trichloroethanoic acid. I is a weak acid and VIII is strong dipping a simple pH electrode into a solution of each of the two acids rapidly demonstrates this truth. 

Xantkates, pyrolysis, 268 X-ray ciyst ography ethanoate anion, 19 Grignard reagents, 221 Meisenheimer complexes, 171 triphenylmethyl rascals, 311... 

Exercise 18-2 Make atomic-orbital models of ethanoic acid and ethanol and of the ethanoate anion and ethoxide anion. Show how these models can be used to explain the greater acidity of ethanoic acid relative to ethanol. 

Exercise 18-3 The Ka for the first ionization of carbonic acid, 0=C(0H)2 + H20 0=C(0H)0e + H30 , is about 1000 times smaller than Ka for ethanoic acid. Show how this fact can be rationalized by considering the expected relative stabilization energies of carbonic acid and the hydrogen carbonate ion compared to those of ethanoic acid and ethanoate anion. 

One of the most easily appreciated is when an acid and its conjugate base bear a different charge, for example when ethanoic acid, CH3C02H, loses a proton to give rise to the ethanoate anion. Write... 

Scheme 9. A representation of the Perkin reaction between ethanoic anhydride (acetic anhydride, CH3CO2COCH3) and benzenecarboxaldehyde (benzaldehyde, C5H5CHO) in the presence of sodium ethanoate (sodium acetate, CH3C02Na) to yield the mixed acetic cinnamic anhydride. The upper part of the scheme indicates nonproductive exchange of ethanoate anion (acetate anion, CH3C02 ) with the anhydride.

A consequence of the high probability of ethanoate anions forming close contacts with the cation through ring C—H... O hydrogen bonding is that anion domains leading to methyl-to-... 

RDF, gives a coordination number of 6.3, which is reduced from 6.8 anions in the first shell around the cation compared with that found in the neat ionic liquid system, as is to be expected owing to the presence of the solute, and is consistent with the idea that the ethanoate anions now also form close contacts with the dissolved sugar as well as with the ionic liquid cations. The total coordination of ethanoate anions around glucose is 6.2, which is somewhat larger than the 3.9 chloride anions, which coordinate to glucose in 1,3-dimethylimidazolium chloride [47, 48]. 

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