Jp. Guthrie, ENERGETICS OF ACETIC-ACID ENOL IN AQUEOUS-SOLUTION - A NEW METHOD FORTHERMODYNAMIC ESTIMATION, Canadian journal of chemistry, 71(12), 1993, pp. 2123-2128
A new disproportionation calculation allows the estimation of the free
energy of formation of the enol of acetic acid as 65 +/- 2 kcal/mol.
The value of pK(E) derived from this free energy, pK(E) = 21 +/- 2, is
in satisfactory agreement with information from the literature about
rates of exchange. Analysis of the data on rates of exchange of the C-
H protons of acetic acid using Marcus theory allows an independent est
imate of the enol content. Exchange in acid and in base lead to intern
ally consistent estimates, pK(E) = 19.3 +/- 2.2, which are within the
combined uncertainties of the values from the thermodynamic estimate.