Ana L. R. Silva, V. Morais, M. D. Ribeiro da Silva
Apr 1, 2016
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0
Influential Citations
8
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Journal
The Journal of Chemical Thermodynamics
Abstract
Abstract This paper reports an experimental and theoretical study on the structural and energetic characterization of the 2-mercaptoimidazole (2-MI) in the solid and in the gaseous phases. The single crystal X-ray diffraction determinations on the anhydrous and hemihydrate 2-MI forms were carried out at T = (296 ± 2) K and T = (150 ± 2) K, respectively, and suggest that in both forms the 2-MI molecule is closer to the thione conformation, albeit some single bond character is possible. The energy of combustion of the title compound was measured by rotating-bomb combustion calorimetry, being used to derive the corresponding enthalpy of formation in the crystalline-phase. The enthalpy of sublimation of 2-MI, at T = 298.15 K, was obtained from high temperature Calvet microcalorimetry measurements. These two parameters yielded the gas-phase enthalpy of formation, allowing the inherent energetic analysis of the molecule. This result was discussed together with the corresponding predictions for 2-MI and its tautomer, 1,3-dihydro-2 H -imidazole-2-thione, by the G3 method. The dehydration reaction of 2-MI · 0.5H 2 O(cr) was also investigated and the corresponding enthalpy of dehydration was determined by Calvet microcalorimetry.