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Effects of alcohols on micellization and on the reaction methyl 4‐nitrobenzenesulfonate + Br − in cetyltrimethylammonium bromide aqueous micellar solutions
Author(s) -
Muñoz María,
del Mar Graciani María,
Rodríguez Amalia,
Moyá María Luisa
Publication year - 2004
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.20039
Subject(s) - chemistry , bromide , micelle , aqueous solution , micellar solutions , reaction rate constant , alcohol , critical micelle concentration , aggregation number , inorganic chemistry , organic chemistry , kinetics , physics , quantum mechanics
Abstract The effects of n ‐hexanol, n ‐pentanol, and n ‐butanol on the critical micelle concentration (cmc), on the micellar ionization degree (α), and on the rate of the reaction methyl 4‐nitrobenzenesulfonate + Br − have been investigated in cetyltrimethylammonium bromide (CTAB) aqueous solutions. An increase in the alcohol concentration present in the solution produces a decrease in the cmc and an increase in the micellar ionization degree. Kinetic data show that the observed rate constant decreases as alcohol concentration increases. This result was rationalized by considering variations in the equilibrium binding constant of the methyl 4‐nitrobenzenesulfonate molecules to the micelles, variations in the interfacial bromide ion concentration, and variations in the characteristics of the water–alcohol bulk phase provoked by the presence of alcohols. When these operative factors are considered, kinetic data in this and other works show that the second‐order rate constants in the micellar pseudophases of water–alcohol micellar solutions are quite similar to those estimated in the absence of alcohols. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 634–641, 2004