Effects of inorganic ions on rate of alkaline hydrolysis of phthalimide inthe presence of cationic micelles

Pseudo-first-order rate constants (k(obs)) for alkaline hydrolysis of phtha limide (PTH) show a monotonic decrease with the increase in the total conce ntration of cetyltrimethylammonium bromide ([CTABr](T))dagger at a constant [NaOH] and [NaBr]. The pseudophase micellar (PM) model and the pseudophase ion-exchange (PIE) model reveal that the rate of alkaline hydrolysis of PT H is insignificant in the micellar pseudophase compared to that in the aque ous pseudophase under different reaction conditions. The CTABr micellar bin ding constants (K-S) of ionized phthalimide (S-) follow an empirical relati onship: K-S=K-S(0)/(1+Psi [MX]) where MX represents NaOH or NaBr. The value of the empirical parameter Psi for HO- is nearly 30-fold smaller than that for Br-. The decrease in K-S with the increase in [HO-] or [Br-] is attrib uted to the expulsion of S- ions from the micellar pseudophase to the aqueo us pseudophase by HO- or Br-. Pseudo-first-order rate constants (k(obs)) fo r alkaline hydrolysis of PTH in the presence of CTABr micelles vary with [M X] (MX=NaBr, KCl and Na2CO3) according to the empirical relationship: k(obs )=(k(obs)(0)+thetaK[MX])/(1+K[MX]) where theta and K are empirical paramete rs. Based upon the values of theta, it is concluded that the respective ani ons Br-, Cl- and CO32- can expel nearly 100, 60 and 15% of the total amount of micellized S- from the micellar pseudophase to the aqueous pseudophase under the limiting conditions where 1 much less thanK[MX].