THE STANDARD ENTHALPIES OF FORMATION OF SOME DIBENZOCYCLOHEPTANE KETONES

The heats of combustion of 10,11-dihydro-5H-dibenzo[a,d]-cycloheptene- 5-one (ketone 1), 5H-dibenzo[a,d]cyclohepten-5-one (ketone 2) and 5,7- dihydro-6H-dibenzo[a,c]cyclo-hepten-6-one (ketone 4) were measured by means of a Gallenkamp adiabatic bomb calorimeter. Uncertainties in the determination of the heats of combustion ranged between 0.25% and 2%. The enthalpies of formation and of atomization for the three compound s were derived. The experimental values of the heats of atomization in the solid state were compared with those calculated using the Allen-S kinner bond energy scheme (for the liquid state). Conclusions concerni ng the resonance energies of the three compounds are drawn.