Investigations of the interactions occurring between the MgO(100) surface and a series of small molecules-methanol, water, and acetic acid-have been performed. The molecule of interest is introduced to a sample cell containing 15-20 MgO(100) crystals and allowed to establish a dynamic equilibrium with the substrate. The adlayer formed on the crystal faces is observed by transmission Fourier transform infrared spectroscopy. The substrates are also inspected with atomic force microscopy both before and after exposure of the surface to the species of interest. The interactions of these adsorbates with MgO(100) under room temperature conditions and pressures on the order of 10 Torr vary from physisorbed methanol to dissociatively chemisorbed acetic acid, which reacts with the MgO(100) forming magnesium acetate under these experimental conditions. (C) 2004 American Vacuum Society.