Reichardt Betaines as Combined Solvatochromic and Acid-Base Indicators in Microemulsions

摘要

Protolytic equilibria and absorption spectra of four solvatochromic Reichardt betaines different in their hydrophobicity are studied in direct microemulsions hydrocarbon-alcohol-surfactant-water(three different hydrocarbons,three alcohols,and seven surfactants including nonionic,cationic,and anionic ones were tested).Localization of even the most lipophilic betaines corresponds to the polarity index E_T~N of no less than 0.4,so that the occurrence of a purely hydrocarbon core in the microdroplets is unlikely probable.The apparent dissociation constants of the indicators are determined,and their dependence on the composition and concentration of the microemulsions is discussed.