A systematic study concerning adsorption and aggregation of chemodegradable, diastereomerically pure sodium cis- and trans-(2-n-allcyl-1,3-dioxan-5-yl) sulfates (alkyl: n-C9H19 and n-C11N23) in the system consisting of n-heptane in contact with aqueous 0.2 M NaCl at 31 degrees 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 (pi), surface excess concentration (Gamma), surface area demand per molecule (A), critical micelle concentration (cmc), standard free energy of adsorption (Delta G degrees(ads)), and of micellization (Delta G degrees(ads)), 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, Delta G degrees(ads), and Delta G degrees(cmc) values are lower for the trans isomers than for the cis ones, whereas the effectiveness of surface tension reduction is nearly the same for both isomers. Additionally, the interfacial tensions of the studied acetal-type isomers have been described for the heptane-aqueous NaCl systems containing Aerosol OT. According to our findings the configuration of the - OSO3-Na polar group at the C-5 carbon atom of the 1,3-dioxane ring, i.e., equatorial in trans isomers and axial in cis isomers, involves diastereomeric differentiation in the aggregation abilities.