Comment on “Density functional theory studies on molecular structure, vibrational spectra and electronic properties of cyanuric acid”

•Extensive bibliography on isomerism of cyanuric acid is presented.•Nine possible isomers of cyanuric acid are characterized computationally.•The tri-oxo tautomer is by far the most stable isomer of cyanuric acid.•The tri-hydroxy form is by more than 100 kJ mol−1 higher in energy than tri-oxo.•Cyanuric acid under all experimental conditions exists as tri-oxo tautomer.

In a recently published paper [Spectrochim. Acta A: Mol. Biomol. Spect. 138 (2015) 711–722], Prabhaharan, Prabakaran, Srinivasan, and Gunasekaran presented a combined experimental and theoretical study on molecular structure, vibrational spectra and NBO analysis of cyanuric acid, and explain their findings using the tri-hydroxy tautomeric form of the compound. In reality, the compound adopts the tri-oxo tautomeric form, which is by over 100 kJ mol−1 more stable comparatively to the tri-hydroxy tautomer discussed and characterized by Prabhaharan et al.

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