THERMODYNAMIC STUDY OF THE 3 ISOMERS OF BROMO AND IODOBENZOIC ACIDS .2.

Using our technique of combustion of small amount of a substance, we d etermined by calorimetry the standard molar enthalpy of formation in t he condensed state and at T = 298.15 K of the three isomers of bromo a nd iodobenzoic acids. Associating to these values their standard molar enthalpies of sublimation previously measured, it was possible to det ermine their standard molar enthalpies of formation in the gaseous sta te and at T = 298.15 K. The experimental values of the thermodynamic p roperties Delta(c)H(m) degrees(cr, 298.15 K), Delta(f)H(m) degrees(cr, 298.15 K), Delta(sub)H(m) degrees(298.15 K), and Delta(f)H(m) degrees (g, 298.15 K) are given for the two series. From the experimental valu e of the standard molar enthalpy of atomization, it was possible to de termine an enthalpy value for the C-b-Br and C-b-I bonds. The experime ntal and theoretical Values of the resonance energy of bromo and iodob enzoic acids are compatible. The relative stability of some monosubsti tuted derivatives of benzoic acid studied in our laboratory is also di scussed.