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

• Type: Article in International Scientific Journal
• Date: 2016

Authors

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

Journal

Title: Thermochimica Acta

Vol. 625

Pages: 36-46

ISSN: 0040-6031

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 8 Citations

Scopus - 8 Citations

Other information

Authenticus ID: 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.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 11