The reactions of nitromethane (CH3NO2) on a thin-film oxide grown on Mo(110) are investigated to gain insight into the role of nitromethane in the catalytic reduction of NO by methane. Using a combination of temperature programmed reaction and infrared reflection-absorption spectroscopy, we find that nitromethane reacts by dissociation of the N-O bonds below 300 K, to yield methylimido (CH3Nads) and terminally-bound oxygen (Mo=O). Methylimido is stable on the surface up to similar to550 K. Dehydrogenation of CH3N to form HCN and H2O is the major pathway; homolytic C-N bond fission to yield gaseous methyl radicals and formaldehyde are minor pathways. Formaldehyde is proposed to form from addition of some methyl radicals to surface oxygen, forming transient methoxy (CH3O), which dehydrogenates to form formaldehdye. Overall, C-N bond retention is favored in the reaction of nitromethane on the thin-film oxide on Mo(110). These results are discussed in the general framework of the CH4-assisted reduction of NO.