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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