BIMOLECULAR FORMATION OF RADICALS BY H-TRANSFER .2. H-TRANSFER REACTIONS OF PHENALENE

The uncatalysed H transfer from phenalane (7) to alpha-methylstyrene 2) and the selfreaction (d) of phenalene (7) are quantitative transformations in the presence of an excess of 9,10-dihydroanthracene (1) (DHA) in diphenyl ether at 200 - 250-degrees-C. In this system phenalene (7) is consumed only in reaction (d) because the phenalenyl radicals (9) are captured by DHA (1) to give phenalene (7) and 9,10-dihydroanthryl radicals (3). The latter disproportionate rapidly. Accordingly, phenalene (7) acts as a catalyst for the hydrogenation of a-methylstyrene (2) by DHA (1). The activation parameters of the two reactions (e) and (d) were obtained from kinetic experiments between 200 - 250-degrees-C. They allow the determination of the C - H bond enthalpy DELTAH(diss) of phenalene (7) (65.3 kcal mol-1) at the methylene position.