Structural and energetic characterization of the tautomers 2-benzothiazolinone and 2-hydroxybenzothiazole

The gas-phase enthalpies of formation of the title compounds, 2-benzothiazolinone and its enol form 2-hydroxybenzothiazole, were estimated computationally from high-level ab initio molecular orbital calculations at the G3(MP2)//B3LYP level of theory. The computed value for the keto form compares very well with the experimental result obtained in this work. The hydroxy ↔ oxo tautomerism of the title compounds was explored in this work as it may be relevant to their ability to occur as different polymorphic forms.