Anca Banciu

The standard enthalpies of formation of some dibenzocycloheptane ketones

The heats of combustion of 10,11-dihydro-5 H-dibenzo[a,d]-cycloheptene-5-one (ketone 1), 5 H-dibenzo[a,d]cyclohepten-5-one (ketone 2) and 5,7-dihydro-6H-dibenzo[a,c]cyclohepten-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.

Flow-vacuum pyrolysis of three dibenzocycloalkanones

Abstract The flow-vacuum pyrolyses of 10H-dibenzo[ a,d ]cyclohepten-10-one ( 9 ); 5H-11,12-dihydrodibenzo[ a,d ]cycloocten-10-one ( 10 ) and 11,12-dihydro-6H-dibenzo[ a,e ]cycloocten-5-one ( 11 ) were studied by GC/MS at 1.33 mbar and temperatures between 600 and 900°C. The ketone 9 affords anthracene and small amounts of anthrone. The product distributions of ketones 10 and 11 are very similar: besides anthracene (major product) and 9-methyl-anthracene (minor product) the 5H-10,11-dihydro-dibenzo[ a,d ]cycloheptene ( 2 ) was formed as an isolable intermediate. Trahanovskys pyrolysis mechanism (including spiranes and bridged diradicals) suggested for dibenzosuberones and dibenzocyclooctanes can be extended to ketones 9 – 11 (as well as to hydrocarbon 2 ). Consideration of enantiomeric spiranes as intermediates can conduct to a better understanding of the reaction mechanism.

Flash vacuum pyrolysis (FVP) on zeolites: Pyrolysis of 5-β (hydroxyethyl)-5H-dibenzo[a,d]cycloheptene

FVP of the title alcohol (9) at 0.65 mbar in argon atmosphere at 350 °C in the presence of seven different acidic zeolites afforded 7H-benzo[c]fluorene (13) and 6,11b-dihydro-7H-ben-zo [c]fluorene (12) as main reaction products. The suggested carbocationic reaction mechanism is supported by: 1. (a) the occurrence of two isomeric dibenzo(C9H10)hydrocarbons, namely 1,1a,6,10b-tetrahydro-1,6-methanodibenzo[a,e]cyclopropa[c]cycloheptene (6) and 9,10-dihydro-9,10-propenoanthracene (5), in the pyrolyses of 9 and 2. (b) by the results of FVP of authentic samples of 6 (conducting mainly to hydrocarbons 12 and 13), respectively 5 (affording to greatest extent the minor products observed in pyrolyses of 9).