title: Experimental and computational thermochemical study of barbituric acids: structure-energy relationship in 1,3-dimethylbarbituric acid.
abstract: This paper reports an experimental and computational thermochemical study on 1,3-dimethylbarbituric acid. The value of the standard (p° = 0.1 MPa) molar enthalpy of formation in the gas phase at T = 298.15 K has been determined. The energy of combustion was measured by static bomb combustion calorimetry, and from the result obtained, the standard molar enthalpy of formation in the crystalline state at T = 298.15 K was calculated as -639.6 ± 1.9 kJ·mol(-1). The enthalpy of sublimation was determined using a transference (transpiration) method in a saturated N(2) stream and a value of the enthalpy of sublimation at T = 298.15 K was derived as 92.3 ± 0.6 kJ·mol(-1). From these results a value of -547.3 ± 2.0 kJ·mol(-1) for the gas-phase enthalpy of formation at T = 298.15 K was determined. Theoretical calculations at the G3 and G4 levels were performed, and a study on molecular and electronic structure of the compound has been carried out. Calculated enthalpies of formation are in very good agreement with the experimental value.
authors.affiliation: Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain. victoriaroux@iqfr.csic.es
authors.forename: María Victoria
authors.initials: MV
authors.lastname: Roux
authors.forename: Rafael
authors.initials: R
authors.lastname: Notario
authors.forename: Concepción
authors.initials: C
authors.lastname: Foces-Foces
authors.forename: Manuel
authors.initials: M
authors.lastname: Temprado
authors.forename: Francisco
authors.initials: F
authors.lastname: Ros
authors.forename: Vladimir N
authors.initials: VN
authors.lastname: Emel'yanenko
authors.forename: Sergey P
authors.initials: SP
authors.lastname: Verevkin
mesh_terms: D001463:Barbiturates / Q000737:chemistry*; D015394:Molecular Structure; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D001463:Barbiturates; C018924:1,3-dimethylbarbituric acid