A chemical principle supporting the priority sequence rule in the systematic nomenclature of organic compounds was sought for. The positions of functional groups containing carbon, hydrogen and oxygen in the priority sequence were examined for possible chemical criteria that could be used to buttress the positions of the functions. Oxidative sequence emerged as possible chemical criteria. This chemical principle was applied to other functions containing nitrogen as well and the result was highly positive. However the position of -C≡C- was not favored, this is commented upon. In general oxidative sequence supports the priority sequence and provides a fast means of deciding which function has higher priority instead of resorting to rote learning.