Article,
A theoretical investigation of the enol content of acetic acid and the acetate ion in aqueous solution
THEOCHEM-JOURNAL OF MOLECULAR STRUCTURE, 370 (2-3): 203--208 (1996)
Abstract
Ab initio molecular orbital calculations and statistical Monte Carlo simulations employing a combined quantum and molecular mechanical potential were used to determine the enol contents of acetic acid and the acetate ion in aqueous solution. A pK(E) of 19.3 +/- 0.3 was predicted for the keto-enol equilibrium of acetic acid, and 21.8 +/- 0.8 for the acetate ion in water. The results are found to be in good accord with Guthrie's calculations based on disproportionation reactions and kinetic data. Combining with the experimental pK(a) value of acetic acid, we obtained pK(a)(K) = 26.6 for ionization of acetic acid as a carbon acid in water, and pK(a)(E) = 7.3 for ionization of the enol of acetic acid.
