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5-Isopropylbarbituric and 2-thiobarbituric acids: An experimental and computational study

Szterner, Piotr ; Galvão, Tiago L.P. ; Amaral, Luísa M.P.F. ; Ribeiro da Silva, Maria D.M.C. ; Ribeiro da Silva, Manuel A.V.

Thermochimica acta, 2016-02, Vol.625, p.36-46 [Periódico revisado por pares]

Elsevier B.V

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  • Título:
    5-Isopropylbarbituric and 2-thiobarbituric acids: An experimental and computational study
  • Autor: Szterner, Piotr ; Galvão, Tiago L.P. ; Amaral, Luísa M.P.F. ; Ribeiro da Silva, Maria D.M.C. ; Ribeiro da Silva, Manuel A.V.
  • Assuntos: 2-Thiobarbituric acid ; 5-Isopropylbarbituric acid ; Combustion ; Combustion calorimetry ; Computation ; Crystal structure ; Enthalpy ; Enthalpy of formation ; Enthalpy of sublimation ; Formations ; G3 and G4 calculations ; Mathematical analysis ; Sublimation
  • É parte de: Thermochimica acta, 2016-02, Vol.625, p.36-46
  • Notas: ObjectType-Article-1
    SourceType-Scholarly Journals-1
    ObjectType-Feature-2
    content type line 23
  • Descrição: •Experimental/computational energetic study of 5-isopropyl and 2-thiobarbituric acids.•Enthalpies of formation of the crystalline compounds from combustion calorimetry.•Enthalpy of sublimation of 5-isopropylbarbituric acid was derived.•Ab initio calculations for the compounds obtained by G3 and G4 methods. The standard (po=0.1MPa) molar energies of combustion, ΔcUmo, for the crystalline 5-isopropylbarbituric and 2-thiobarbituric acids were determined, at the temperature of 298.15K, by static bomb or rotating bomb combustion calorimetry, respectively. For 5-isopropylbarbituric acid, the standard molar enthalpy of sublimation, ΔcrgHmo, at T=298.15K, was derived by Calvet microcalorimetry. The standard molar enthalpy of sublimation, at T=298.15K, was derived by the Clausius–Clapeyron equation, from the temperature-vapor pressure dependence, measured by the Knudsen mass-loss effusion method. These experiments allowed the determination of the standard molar enthalpy of formation, in the gaseous phase, at T=298.15K for 5-isopropylbarbituric acid. For 2-thiobarbituric acid, the gas-phase enthalpy of formation was calculated combining the result derived for the crystalline phase with literature data for the enthalpy of sublimation, at T=298.15K. These values were compared with estimates obtained from very accurate computational calculations using the G3 and G4 level theory composite methods.
  • Editor: Elsevier B.V
  • Idioma: Inglês;Holandês
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