Catalytic effect of anionic micelles on alkaline hydrolysis of N-hydroxyphthalimide. Evidence for the probable occurrence of the reaction in between Gouy-Chapman and exterior boundary of Stern layers of the micelles
✍ Scribed by M. Niyaz Khan
- Publisher
- John Wiley and Sons
- Year
- 1991
- Tongue
- English
- Weight
- 717 KB
- Volume
- 23
- Category
- Article
- ISSN
- 0538-8066
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✦ Synopsis
Abstract
The nucleophilic second‐order rate constant (k~OH~) for the reaction of ŌH with ionized N‐hydroxyphthalimide (S^−^) appears to follow a reaction mechanism similar to that for reactions of ŌH with neutral phthalimide and its N‐substituted derivatives. Kinetically indistinguishable terms, k′~w~[H~2~O][S^−^] and k~ŌH~[ŌH][SH] (SH represents nonionized N‐hydroxyphthalimide), which constitute the pH‐independent rate region of the pH‐rate profile, are resolved qualitatively. It is shown that the term k~ŌH~[ŌH][SH], rather than k′~w~[H~2~O][S^−^], is important in these reactions. The rates of ŌH‐catalyzed cleavage of S^−^ were studied at 32° in the presence of micelles of sodium dodecyl sulphate (SDS). At a constant [ŌH], the observed pseudo first‐order rate constants (k~obs~) increase linearly with [SDS]~T~ (total SDS concentration). These data are explained in terms of the pseudophase model of micellar effects on reactivity. The linear dependence of k~obs~ with [SDS]~T~ (within [SDS]~T~ range of 0.0–0.2 or 0.3 M) is attributed to the occurrence of the reaction between the exterior boundary of Stern layer and Gouy‐Chapman layer.