Derivatives of phenols, such as o-aminophenol, m-aminophenol, p-aminophenol, o-dihydroxybenzene, m-dihydroxybenzene, and p-dihydroxybenzene were phosphorylated by diethyl phosphite (DEPH) using simplified Atherton-Todd method and then the resulting di-phosphorylated compounds were injected into an ion-trap mass spectrometer and exposed to MS/MS analysis. Results showed that the cleavage pathways of these phosphorylated compounds were closely related to the relative positions of the phosporylating groups. Comparatively stable five-membered ring ions were produced when the two phosphorylated functional groups were in the ortho position. These stable five-membered ring ions can be considered as indicators for ortho functional groups of phenols.