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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
Author(s) -
Khan M. Niyaz
Publication year - 1991
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550230703
Subject(s) - chemistry , reaction rate constant , micelle , phthalimide , reactivity (psychology) , catalysis , nucleophile , medicinal chemistry , hydrolysis , reaction rate , kinetics , organic chemistry , aqueous solution , medicine , physics , alternative medicine , pathology , quantum mechanics
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.