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 compounds were derived. The experimental values of the heats of atomization in the solid state were compared with those calculated using the Allen-Skinner bond energy scheme (for the liquid state). Conclusions concerning the resonance energies of the three compounds are drawn.