Energetic characterization of uracil derivatives: orotic and isoorotic acids

Publication date: Available online 2 December 2019Source: Thermochimica ActaAuthor(s): Luísa M.P.F. Amaral, Piotr Szterner, Victor M.F. Morais, Maria D.M.C. Ribeiro da Silva, Manuel A.V. Ribeiro da SilvaAbstractThe standard (po =0.1 MPa) molar enthalpies of formation of orotic and isoorotic acids, in the crystalline phase, were derived from the respective standard massic energies of combustion measured by static bomb combustion calorimetry, in oxygen, at T =298.15 K, as ‒821.7 ± 1.1 kJ·mol-1 and ‒838.3 ± 1.9 kJ·mol-1, respectively.The molecular structure and conformational behaviour of orotic and isoorotic acids were studied by theoretical calculations and the standard gas-phase molar enthalpies of formation were derived using an appropriate set of working reactions.Sublimation enthalpies, at the reference temperature T =298.15 K, were estimated from difference between crystalline and gaseous enthalpies of formation and from statistically-based interaction indices derived from molecular surface electrostatic potentials.Graphical Abstract

Source: Thermochimica Acta - December 3, 2019 Category: Chemistry Source Type: research