Effects of polymer and salt concentrations on ketal acid hydrolysis in solutions of sodium dodecyl sulfate and poly(vinyl pyrrolidone) or poly(ethylene oxide)

The acid-catalyzed hydrolysis of 2-(methoxyphenyl)-1,3-dioxolane (p-MPD) and di-n-butyl benzaldehyde acetal (BBA) has been studied in solutions containing poly(ethylene oxide) (PEG) or poly(vinyl pyrrolidone) (PVP) and sodium dodecyl sulfate (SDS). First-order rate constant-[SDS] profiles were obtained at 0.010 and 0.105 M PEO or PVP, and both polymers strongly inhibit the reaction, to an extent depending on the polymer and SDS concentrations. Added NaCl also decreases the rate, and the behavior is similar to that with SDS micelles. The inhibition induced by increasing polymer concentration was interpreted by assuming decreases in the interfacial H+ concentration. This conclusion is supported by values of pH apparent obtained with the pH indicator pyridine-2-azo-p-dimethylaniline (PADA) at the same experimental kinetic conditions. Qualitatively, the results are interpreted in terms of the pseudophase ion exchange (PPIE) model applied to bimolecular reactions.