Adsorption of Diastereomerically Pure Sodium cis- and trans-(2-n-Alkyl-1,3-dioxan-5-yl) Sulfates at the n-Heptane−Water Interface

Abstract

A systematic study concerning adsorption and aggregation of chemodegradable, diastereomerically pure sodium cis- and trans-(2-n-alkyl-1,3-dioxan-5-yl) sulfates (alkyl: n-C9H19 and n-C11H23) in the system consisting of n-heptane in contact with aqueous 0.2 M NaCl at 31 °C has been undertaken. The role of the six-membered 1,3-dioxane ring has been discussed in terms of comparison between studied surfactants and “classical” sodium decyl and dodecyl sulfates. Surface parameters of compounds under study at the oil−water interface, i.e., surface tension reduction (π), surface excess concentration (Γ), surface area demand per molecule (A), critical micelle concentration (cmc), standard free energy of adsorption (ΔGoads), and of micellization (ΔGocmc), show differences due to the alkyl chain length and to the hydrophilic, i.e., sulfate group configuration at the C-5 atom of the 1,3-dioxane ring. The cmc, ΔGoads, and ΔGocmc values are lower for the trans isomers than for the cis ones, whereas the effectiveness of...