ИСТИНА

Temperature dependences of the vaporization enthalpies, ∆vapH , were determined for three biphenyls, namely 1, 1’- biphenyl (BP), 4-nitrobiphenyl (4-NBP) and 3-iso-propylbiphenyl (3-IPBP) on an isothermal heat conducting Calvet micro calorimeter with an estimated accuracy of ≤ 1.0 per cent in the 323 K to 373 K range. The average values ∆vapH were adjusted to 298.15 K. Treatment of the data for three biphenyls was carried out by the least square method to get the analytical dependence of vaporization enthalpy on temperature, ∆vapH /kJ•mol-1 = α + β (T /K). Formation enthalpies of some biphenyl derivatives have been determined in a gas phase. On the base of “double the difference” method the novel scheme for enthalpies of formation of aromatic radicals calculations have been suggested. The scheme allows to exclude the energies of reorganization of molecules fragments into radicals and to determine the enthalpies of formation for radicals and energies of dissociation for chemical bonds using the enthalpies of atomization. On the basis of the proposed scheme the enthalpy of formation for biphenyl-4-yl has been calculated.