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

Abstract

This work reports an experimental and computational thermochemical study for 2-benzothiazolinone. The standard (p°=0.1MPa) molar energy of combustion of this compound was measured by rotating bomb combustion calorimetry. The standard molar enthalpy of the corresponding transition from crystalline to gaseous phases, at T=298.15K, was obtained from high temperature Calvet microcalorimetry measurements. The experimental results enable the calculation of the standard molar enthalpy of formation of the compound, in the gaseous state, at T=298.15K.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.