Limiting enthalpies of solution of several bifunctional compounds (1,2-dimethoxyethane, 2-methoxyethanamine, 2-methoxyethanol, 2-aminoethanol, 1,4-dioxane, morpholine, 4-methylmorpholine, 1-methylpiperazine) in water/octan-1-ol mixtures, with water content ranging from zero to saturation, have been determined at 25°C. The observed phenomenology has been interpreted according to a model of microphase transition involving the solvent medium. In the low water content range, water acts as prevailingly monodispersed, whereas above 0.1 mole fraction water the formation of pseudomicellar water aggregates can be inferred and a simple model of phase distribution can be applied to describe the observed trends.