Solubilization of Aliphatic Carboxylic Acids (C3-C6) by Sodium Dodecyl Sulfate and Brij 35 Micellar Pseudophases

The apparent dissociation constants of 1-propanoic, 1-butanoic, 1-pentanoic and 1-hexanoic acids were obtained for the first time in Brij 35 micellar solutions with concentration from 0.03 to 0.20 mol⋅L⁻¹ and sodium dodecyl sulfate (SDS) micellar solutions with concentrations from 0.01 to 0.30 mol⋅L⁻¹. A pronounced effect of Brij 35 micelles on the acid-base properties of aliphatic acids was observed. The binding constants, K _b, of carboxylic acids to micellar pseudophases of SDS and Brij 35 were estimated within the framework of the pseudophase model. The dependences of Gibbs energies of transfer from water to the micellar pseudophases were constructed, and Gibbs energies were evaluated for methylene and carboxylic group transfers into Brij 35 and SDS micelles. Comparison of the Gibbs energies of methylene group transfer from water to Brij 35 and SDS suggests that the mechanisms of hydrocarbon group transfer into the core of nonionic and anionic micelles involving the same monomer hydrophobic tail length are similar.