Vibrational and photoelectron spectroscopies have become useful tools for identifying adsorbed aromatics and their orientation on surfaces. The adsorption geometry of aromatics, such as benzene, pyridine, and triazine on Al has been deduced. On sp-metal surfaces such as on Al, benzene has been shown to adsorb in a flat-lying geometry. Although the bonding orientation is similar to that of transition metals, the bonding interaction is different with only a weak benzene-Al interaction. For the adsorption of pyridine at low temperatures and low coverages, the molecular plane is parallel to the surface plane. At higher coverages, the molecular plane tilts toward the surface normal and is bonded through the nitrogen lone pair. We have previously reported on the chemisorption of triazine on an Al (111) surface using X-ray photoelectron spectroscopy (XPS) and infrared reflection absorption spectroscopy. The data showed that some s-triazine molecules dissociatively chemisorb on the Al surface, while others adsorb intact and bond to the surface through a nitrogen lone pair. The data revealed the molecular plane of the intactly adsorbed triazine is tilted with respect to the substrate surface plane. In this work, X-ray photoelectron spectroscopy (XPS) is used to characterize the interaction of 1,3,5-trinitro-1,3,5 triazine (RDX) with Al. XPS is used to determine the chemical species at the RDX/Al interface. Besides its usefulness as a tool for chemical analysis, XPS is useful in examining changes to chemical states of materials. For RDX, the spectrum of the N 1s region has two easily discernable peaks assigned to the nitro group and ring structure nitrogen. Upon the initial interaction of aluminum with RDX, the N 1s spectrum reveals that the nitrogen peak associated with the nitro group is diminished compared to that of the ring structure. This is an indication of the preferential reaction of the nitro group with the aluminum, leaving the ring structure intact.