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. (X_Λ) of R'OH bound to the microemulsions. their mole fraction partition constants K_Λ). and mass action binding constants (K_Λ). Values of K_Λ). decrease with added R'OH consistent with literature results, Unexpectedly, values of K_Λ' are constant at all values of X_Λ. 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.