Thermochemistry of 6-propyl-2-thiouracil: An experimental and computational study

• Published in: Thermochimica acta 2014-07, Vol.588, p.68-74
• Main Authors: Szterner, Piotr, Galvão, Tiago L.P., Amaral, Luísa M.P.F., Ribeiro da Silva, Maria D.M.C., Ribeiro da Silva, Manuel A.V.
• Format: Article
• Language: English
• Subjects: 6-Propyl-2-thiouracil; Carbon dioxide; Combustion; Computation; Energy of combustion; Enthalpy; Enthalpy of formation; Formations; G3 and G4 calculations; Knudsen effusion method; Mathematical analysis; Thermochemistry; Vapor pressure
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/j.tca.2014.04.018

•Thermochemistry of 6-propyl-2-thiouracil – experimental and computational study.•Vapor pressure study of the 6-propyl-2-thiouracil by Knudsen effusion technique.•Enthalpies of formation of 6-propyl-2-thiouracil by rotating combustion calorimetry.•Accurate computational calculations (G3 and G4 composite methods) were performed. The standard (po=0.1MPa) molar enthalpy of formation of 6-propyl-2-thiouracil was derived from its standard molar energy of combustion, in oxygen, to yield CO2 (g), N2 (g) and H2SO4·115H2O (l), at T=298.15K, measured by rotating bomb combustion calorimetry. The vapor pressures as function of temperature were measured by the Knudsen effusion technique and the standard molar enthalpy of sublimation, ΔcrgHmo, at T=298.15K, was derived by the Clausius–Clapeyron equation. These two thermodynamic parameters yielded the standard molar enthalpy of formation, in the gaseous phase, at T=298.15K: −(142.5±1.9)kJmol−1. This value was compared with estimates obtained from very accurate computational calculations using the G3 and G4 composite methods.