Journal of Chemical Thermodynamics, Vol.30, No.7, 869-878, 1998
Enthalpies of combustion of the pyridine N-oxide derivatives : 4-methyl-, 3-cyano-, 4-cyano-, 3-hydroxy-, 2-carboxy-, 4-carboxy-, and 3-methyl-4-nitro, and of the pyridine derivatives : 2-carboxy-, and 4-carboxy-. The dissociation enthalpies of the N-O bonds
The standard (p degrees = 0.1 MPa) molar enthalpies of formation Delta(f)H(m)degrees(cr) at T = 298.15 K were determined using static-bomb calorimetry for crystalline 4-methylpyridine N-oxide (4MePyNO), 3-cyanopyridine N-oxide (3CNPyNO), 4-cyanopyridine N-oxide (4CNPyNO), 3-hydroxypyridine N-oxide (3OHPyNO), 2-pyridinecarboxylic acid N-oxide (2CO(2)HpyNO), 4-pyridinecarboxylic acid N-oxide (4CO(2)HPyNO), 3-methyl-4-nitropyridine N-oxide (3Me4NO(2)PyNO), 2-pyridinecarboxylic acid (2CO(2)HPy), and 4-pyridinecarboxylic acid (4CO(2)HPy). The standard molar enthalpies of sublimation Delta(c)(rg) H(m)degrees at T = 298.15 K were measured by microcalorimetry, or by a mass-loss effusion technique, and from the enthalpies of formation of the gaseous compounds the dissociation enthalpies D(m)degrees of the (N+-O-) dative covalent bonds were derived.Comparison has been made with D(m)degrees(N-O) values in pyridine N-oxide derivatives.