Density functional theory calculations allowed us to study alloxydim herbicide and to identify the most stable conformers, the factors that governs their stability, and the interconversion mechanisms among the most relevant conformers. The degradation chain involves, as a first step, the cleavage of the N-O bond and the formation of a stable intermediate difficult to characterize experimentally. The study performed also allowed us to identify the properties of this elusive intermediate and to determine that the dominant fragmentation process in the gas phase is the homolytic fragmentation. Stability of alloxydim conformers and homolytic fragments were also assessed in the water phase. Computed IR spectra were consistent with those observed experimentally.