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

• Tipo: Artigo em Revista Científica Internacional
• Data: 2016

Autores

Piotr Szterner (Autor) Outra; Tiago L.P Galvão (Autor) Outra; Luísa M.P.F Amaral (Autor) Outra; Maria D.M.C Ribeiro da Silva (Autor) FCUP; Manuel A.V Ribeiro da Silva (Autor) Outra

Revista

Título: Thermochimica Acta

Vol. 625

Páginas: 36-46

ISSN: 0040-6031

Editora: Elsevier

Indexação

ISI Web of Knowledge - 8 Citações

Scopus - 8 Citações

Outras Informações

ID Authenticus: P-00J-Z31

DOI: 10.1016/j.tca.2015.12.007

Abstract (EN): The standard (p(0) = 0.1 MPa) molar energies of combustion, Delta U-c(m)0, for the crystalline 5-isopropylbarbituric and 2-thiobarbituric acids were determined, at the temperature of 298.15 K, by static bomb or rotating bomb combustion calorimetry, respectively. For 5-isopropylbarbituric acid, the standard molar enthalpy of sublimation, Delta H-g(cr)m(0), at T=298.15 K, was derived by Calvet microcalorimetry. The standard molar enthalpy of sublimation, at T=298.15 K, 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=298.15 K 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=298.15 K. These values were compared with estimates obtained from very accurate computational calculations using the G3 and G4 level theory composite methods.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 11