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Surfactant effects on the reaction of 2‐(4‐cyanophenoxy)‐quinoxaline with hydroxide ion
Author(s) -
Cuenca Angela
Publication year - 2006
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.20163
Subject(s) - chemistry , hydroxide , pulmonary surfactant , reaction rate constant , quinoxaline , micelle , substrate (aquarium) , reaction rate , ion , inorganic chemistry , nucleophilic substitution , alkyl , nucleophile , medicinal chemistry , kinetics , organic chemistry , aqueous solution , catalysis , biochemistry , physics , oceanography , quantum mechanics , geology
A reaction of 2‐(4‐cyanophenoxy)quinoxaline 1 with hydroxide ion is accelerated by supramolecular aggregates of cetyltrialkylammonium chlorides (alkyl = Me, n ‐Pr, and n ‐Bu). In diluted surfactant solutions, with relatively high substrate concentration (7.0 × 10 −5 M), rate constants go through double rate maxima with increase in the surfactant concentration. The first rate maximum is ascribed to a reaction occurring in premicellar aggregates and the second to reaction in micelles. At low substrate concentration (7 × 10 −6 M), second‐order rate constants in the micellar pseudophase are dependent on the surfactant headgroup size, which is related to charge dispersion in the transition state. Nonmicellizing tri‐ n ‐octylmethylammonium ions (TOAMs) increase the reaction of 1 with hydroxide ion. The observed rate enhancements may be due to the formation of small, hydrophobic aggregates which bind the substrate and promote the nucleophilic substitution reaction. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 510–515, 2006