RESONANT-SURFACE 2ND-HARMONIC GENERATION STUDIES OF PHENOL DERIVATIVES AT AIR WATER AND HEXANE/WATER INTERFACES/

Resonant-surface second-harmonic generation and surface tension measur ements have been used to study the adsorption of p-nitrophenol, phenol and p-propylphenol at the air/water and hexane/water interfaces at fu ll monolayer coverage. The determining forces defining the angle of or ientation of the moieties are the solute-solvent interactions at both interfaces. In particular, we observed the screening effect of the hex ane phase on the solute-water interactions. Surface tension measuremen ts performed on these interfaces showed that the number of molecules p er unit surface at full coverage follows from the angle of orientation . From a wavelength analysis of the SH response of the monolayers, we are led to the conclusion that partial hydration of the aromatic rings of phenol and p-propylphenol occurs at both the air/water and the hex ane/water interfaces, whereas p-nitrophenol remains largely within the water phase at both interfaces.