Ketonization of enols in aqueous solution: is carbon protonation always rate-determining?
| Autoři | |
|---|---|
| Rok publikování | 2012 |
| Druh | Článek v odborném periodiku |
| Časopis / Zdroj | PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES |
| Fakulta / Pracoviště MU | |
| Citace | |
| www | Full Text |
| Doi | http://dx.doi.org/10.1039/c2pp05369a |
| Klíčová slova | KETO-ENOL; DISSOCIATION-CONSTANT; BUFFER SOLUTIONS; ACID; HYDRATION; SYSTEM |
| Popis | The pH-rate profiles for the ketonization of the (E)- and (Z)-photoenols of o-methylacetophenone (MA) in aqueous solution were determined by nanosecond laser flash photolysis. Carbon protonation of the enol anions of MA by solvent water is exceptionally fast, k(0)'K approximate to 2.0 x 10(7) s(-1), too fast to permit establishment of the acid-base equilibrium on the enol oxygen prior to ketonization. Analysis of the pH-rate profile of the (E)-enol using the common assumption of rate-determining carbon protonation would lead to an erroneous value for the acidity constant of that enol, pK(a,c)(E) = 11.3, which is too high by about two pK units. |
| Související projekty: |