title: The energetics of isomeric benzoxazine diones: isatoic anhydride revisited.
abstract: The standard (p(o) = 0.1 MPa) molar enthalpy of formation of crystalline 2H-1,3-benzoxazine-2,4(3H)dione was measured, at T= 298.15 K, by static bomb calorimetry and the standard molar enthalpy of sublimation, at T= 298.15 K, was obtained using Calvet microcalorimetry. These values were used to derive the standard molar enthalpy of formation in the gaseous phase, T= 298.15 K, of -(401.0 +/- 3.5) kJ mol(-1). The standard molar enthalpy of sublimation of isatoic anhydride was recalculated, and our recommended experimental value for the standard molar enthalpy of formation in the gaseous phase, T= 298.15 K, is -(406.2 +/- 3.4) kJ mol(-1). Density functional calculations for the two isomers 2H-1,3-benzoxazine-2,4(3H)dione and isatoic anhydride, in which the ring nitrogen and oxygen have been transposed, confirm the experimental evidence of nearly identical thermochemical stability for these isomers.
authors.affiliation: Centro de Investigação em Química, Departamento de Química, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 687, P-4169-007 Porto, Portugal. marmatos@fc.up.pt
authors.forename: M Agostinha R
authors.initials: MA
authors.lastname: Matos
authors.forename: Margarida S
authors.initials: MS
authors.lastname: Miranda
authors.forename: Victor M F
authors.initials: VM
authors.lastname: Morais
authors.forename: Joel F
authors.initials: JF
authors.lastname: Liebman