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Deprotonation of Indole Derivatives in Aqueous Cationic Surfactants



Deprotonations of 5-nitroindole, 1a, and its 2-carboxylate ion, 2a, have been monitored in 0.01, 0.1, and 0.5 M NaOH in micellar solutions of cetyl trialkylammonium bromide, alkyl = Me, Et, nPr, nBu, CTABr, CTEABr, CTPABr, CTBABr. Extents of deprotonation (% f) have been fitted using the pseudophase model of micellar effects with interionic competition described by ion exchange or by independent association constants. Both treatments indicate that base dissociation constants in dilute OH are lower than in water by factors of ca. 3−11, and decrease with increasing bulk of the head groups, and that these factors increase modestly as the OH concentration increases to 0.5 M. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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