The standard (pdegrees = 0.1 MPa) molar enthalpies of formation, at T = 298.15 K, were determined using static-bomb calorimetry for crystalline 6-methoxyquinoline N-oxide (6MeOQU-INO), as -(85.6 +/- 3.7) kJ . mol(-1) and liquid 6-methoxyquinoline (6MeOQUI), -(25.8 +/- 2.2) kJ . mol(-1). The standard molar enthalpies of sublimation/vaporization, at T = 298.15 K, were measured by microcalorimetry and from the enthalpies of formation of the gaseous compounds, the dissociation enthalpy D-m(0) of the (N+-O-) dative covalent bond was derived, as (269.2 +/- 5.0) kJ . mol(-1). @ 2003 Elsevier Science Ltd. All rights reserved.