The hydrolytic pseudo-first-order rate constants (kad) ofp-nitrophenyl esters of dodecanoic acid (C12) and hexadecanoic acid (C16) at different initial substrate concentrations ([S]i) in the six aquiorgano binary mixtures of different compositions (ϕ) were measured. These rate constants (kad) were compared with the corresponding rate constants obtained in the absence of sodium carboxymethylamylose (Na-CMA) (kun) in order to study the competition between the formation of inclusion complexes of these esters with Na-CMA and the aggregation of these long-chain substrates. Values of ΔCAgC andkad/kun were compiled and their significance discussed on the basis of a postulated two-path mechanism. Our results suggest that in addition to path A which involves encapsulation by Na-CMA of the monomeric C12 or C16 only, there is a second path (path B). Path B describes a process in which Na-CMA breaks up aggregates of all sizes into smaller ones as well as monomeric species which can be wrapped-up by Na-CMA simultaneously or subsequently.
Volume 134, 2022
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