Hydration of p-Alkyloxy-alfa,alfa,alfa-trifluoroacetophenone and Water Activity at a Micellar Surface

Equilibrium hydration of p-methoxy-α-α-α-trifluoroacetophenone (MTFA) in water and anionic micelles of sodium dodecyl sulfate (SDS) has been followed by 19F NMR and UV spectrometry, and is strongly disfavored by the micelles. The effects can be separated into those due to the different transfer equilibria of the carbonyl and hydrate forms and to a decrease in water activity in the micelles. The transfer equilibria of the carbonyl and hydrate forms of MTFA between water and micelles have been followed by NMR spectrometry and an activity of water at the micellar surface of 0.6 has been determined. Attainment of hydration equilibrium in water, aqueous acetonitrile, and micelles has been followed by UV spectrometry and rate constants for forward and reverse reactions have been calculated. The overall equilibrium of the p-octyloxy derivative has been examined in aqueous acetonitrile and SDS micelles. The hydrophobic octyl group reduces the rate and equilibrium constants of hydration.