Arenediazonium salts: new probes of the interfacial compositions of association colloids. 2. Binding constants of butanol and hexanol in aqueous three-component cetyltrimethylammonium bromide microemulsions

Abstract

Yields of aryl ether products, 16-ArOR'. were determined by HPLC with excellent reproducibility from dediazoniation of 4-hexadecyl.2.6-dimethylbenzcnediazonium tetrafluoroborate (l6-ArN2BF4) bound to surfactant aggregates in three-component microemulsions of cetyltrimethylammonium bromide ((CTA)Br).H2O. and an alcohol (R'OH), either I-butanol (BuOH) or l-hexanol (HexOH). The results were used to estimate the mole fraction. (XΛ) of R'OH bound to the microemulsions. their mole fraction partition constants KΛ). and mass action binding constants (KΛ). Values of KΛ). decrease with added R'OH consistent with literature results, Unexpectedly, values of KΛ' are constant at all values of XΛ. indicating that (CTA)Br mixes ideally with both BuOH and HexOH in aqueous microemulsions and that binding of R'OH to (CTA)Br microemulsions is driven by a hydrophobic effect with minimal contributions from specific interactions between R'OH and (CTA)Br.