Bimolekulare Radikalbildung durch H‐Transfer, 2. H‐Transferreaktionen mit Phenalen

Abstract

Bimolecular Formation of Radicals by H‐Transfer, 2 [1] . – H‐Transfer Reactions of Phenalene The uncatalysed H transfer from phenalane ( 7 ) to α1‐methyl‐styrene ( 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°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 α1‐methylstyrene ( 2 ) by DHA ( 1 ). The activation parameters of the two reactions (e) and (d) were obtained from kinetic experiments between 200–250°C. They allow the determination of the CH bond enthalpy δ H diss of phenalene ( 7 ) (65.3 kcal mol –1 ) at the methylene position.