By taking the IR spectra of several cyclotriphosphates of a resolved structure, has subsequently shown that it is possible to characterize the PO ring by its IR spectrum and, in some favorable cases, to make them Predicted symmetry of the cycle by examining the number, profile and position of the observed infrared bands in the symmetric valence vibration of the POP (νs POP) groups. He identified criteria for each type of symmetry and discussed, using concrete examples, the limits of the infrared method in determining the symmetry of the cycle (all the possible symmetries that a PO cycle can have). Recently, at the Laboratory, studies have been undertaken by A. ABOUIMRANE et al. [1] for the calculation of the normal IR frequencies of the PO cycle for the ideal and real symmetries: D, C and C (Tables 1,2 and 3). Published by Elsevier Inc. This is an open access article under the CC BY license https://doi.org/10.1080/10426507.2017.1333507.