Acid dissociation constants of N-alkyl p/o-hydroxy styryl pyridinium dyes in surfactant solutions

Some N-alkyl p/o-hydroxy styryl pyridinium halides, the alkyl moieties bein g methyl, hexyl and decyl, have been synthesised and the acid dissociation constants of these compounds in aqueous and surfactant solutions have been determined using spectrophotometric method. The alkyl chain does not have a ny substantial effect on the pK(a) values in aqueous and cationic surfactan t (cetyl trimethylammonium bromide: CTAB) system. However, with longer alky l chain the pK(a) values increase in anionic surfactant (sodium dodecyl sul phate: SDS). These results have been attributed to the variation in solubil ization sites of the surfactants.