Adsorption properties of diastereomeric 2-n-alkyl-5-methoxy-1,3-dioxanes at the air/water interface

The adsorption properties of diastereomerically pure cis- and trans-2-n-alk yl-5-methoxy-1,3-dioxanes (alkyl: n-C3H7, n-C4H9, and n-C5H11) at the air/w ater inter-face at 295 K were investigated using surface tension measuremen ts of surface-chemically pure solutions. The surface parameters, i.e., the standard free energy of adsorption, Delta G(ad)(o), the minimum surface are a demand per molecule adsorbed, A(min), and the surface interaction paramet er, HS, reveal distinct differences with respect to the molecules' stereoch emistry. The adsorption parameters of these compounds are compared with tho se of the related cis- and trams-2-n-alkyl-5-hydroxy-1,3-dioxane derivative s. The surface parameters standard free energy and surface interaction of t he corresponding homologous series of the cis- and trans-2-n-alkyl-5-methox y-1,3-dioxanes and of the cis- and trans-2-n-alkyl-5-hydroxy-1,3-dioxanes d iffer considerably. However, the cross-sectional areas of the two cis and t rans homologous series each approach practically identical limiting values.