A number of nonionic surfactants were synthesized from pelargonic and tridecanoic acids and propylene oxide in the presence of organic and inorganic bases using a wide range of molar ratios of reactants, The influence of organic and inorganic bases on oxylyropylation process was studied. Synthetic products were identified by NMR and IR spectroscopy methods. The surface activity of oxypropylates was studied by the dropweight technique, and the causes of their surface activity were revealed. In the cases when the interfacial tension is stabilized with increasing concentration of oxypropylates in solution, surface tension isotherms were constructed and different quantities characterizing the surfactant properties of the products were calculated.