VAPOR-PRESSURES AND STANDARD MOLAR ENTHALPIES OF SUBLIMATION OF 7 CRYSTALLINE COPPER(II) BETA-DIKETONATES - THE MEAN MOLAR (CU-O) BOND-DISSOCIATION ENTHALPIES

Vapour pressures as functions of temperature of seven crystalline copp er(II) beta-diketonates, CuL(2), were measured using either the Knudse n mass-loss effusion technique (Oporto apparatus), the simultaneous to rsion and mass-loss effusion technique (Utrecht apparatus), or both. F rom the temperature dependence of the vapour pressure, the standard mo lar enthalpies of sublimation, at the mean temperature of the experime ntal temperature range, Delta(cr)(g) H-m degrees ((T)), were derived, and the standard molar enthalpies of sublimation, at the temperature 2 98.15 K, were calculated: [GRAPHICS] where HACAC, pentane-2,4-dione; H PIPRM, 2,2-dimethylheptane-3,5-dione; HDIBM, 2,6-dimethylheptane-3,5-d ione; HIBPM, 2,2, 6-trimethylheptane-3,5-dione; HDPM, 2,2,6,6-tetramet hylheptane-3,5-dione; HBZAC, 1-phenylbutane-1,3-dione; and HTFAC, 1,1, 1-trifluoropentane-2,4-dione. The consistency of the vapour-pressure m easurements was tested by measuring the vapour pressures of benzoic ac id, at various temperatures, by different experimental techniques: Knu dsen mass-loss effusion, simultaneous torsion and mass-loss effusion t echnique, and spinning rotor. From the standard molar enthalpies of fo rmation of the gaseous complexes, the mean molar (Cu-O) bond-dissociat ion enthalpies were derived.