Monolayers of 3-(12-mercaptododecyl)phenol and 4-(12-mercaptododecyl)phenol are prepared to investigate the relationship between the interfacial molecular structure and the surface energy of modified interfaces. These modified interfaces are characterized by reflection absorption infrared spectroscopy, reductive desorption, and contact angle measurements. Contact angle measurements with water (γ = 72.0 mN/m), glycerol (γ = 63.2 mN/m), and ethylene glycol (γ = 48.1 mN/m) show that monolayers of 4-(12-mercaptododecyl)phenol have a higher surface energy (42 mN/m) than 3-(12-mercaptododecyl)phenol monolayers (31 mN/m). Furthermore, Fowkes analysis of the contact angle data show that only 8% of the surface energy of the 4-(12-mercaptododecyl)phenol monolayer arises from dispersive interactions, while 30% of the total surface energy of 3-(12-mercaptododecyl)phenol monolayers comes from dispersive interactions. These surface energy results along with the spectral data suggest that the hydroxyl group with monolayers of 4-(12-mercaptododecyl)phenol is oriented away from the substrate and into the adjacent phase more than is found with monolayers of 3-(12-mercaptododecyl)phenol.