STUDIES ON THE SURFACE FREE-ENERGY COMPONENTS OF NITROFURANTOIN

Surface free energy components, apolar Lifshitz-van der Waals, γSLW, and polar electron donor, γS-, and electron acceptor, γS-, have been determined for nitrofurantoin (N-(5-nitro-2-furfurylidene)-1-aminohyantoin) by both contact angle measurements and the thin-layer wicking technique. The best agreement between the values obtained by these two methods was found when water, formamide, tetrabromoethane, and n-decane were used as probe liquids. The averaged values of the surface free energy components were γSLW = 48.0, γS- = 25.1, and γS+ = 7.0 mJ/m2, thus giving the value 74.5 mJ/m2 for the total surface free energy of nitrofurantoin. Based on these values, the free energy of interaction, ΔG121, between particles of nitrofurantoin immersed in water was calculated to be -10.6 mJ/m2, thus demonstrating the possibility of the aggregation process if the electrostatic repulsions do not prevent it. Justification for the determined free energy components is given considering the nitrofurantoin molecular structure. © 1992.