CYCLOPENT[bc]ACENAPHTHYLENE: A PUTATIVE INTERMEDIATE ON THE PATHWAY FOR THERMAL CYCLODEHYDROGENATION OF PHENANTHRENE

Phenanthrene, the archetypal obay regiono polycyclic aromatic hydrocarbon (PAH), loses two hydrogen atoms when subjected to flash vacuum pyrolysis (FVP) at 1100 degrees C and suffers a major skeletal rearrangement to form pyracylene (1), along with 1-, 3-, and 4-ethynylacenaphthylene (2, 3, and 4, respectively). Evidence is presented that implicates cyclopenta[bc]acenaphthylene (7) as a key intermediate on the reaction pathway from phenanthrene to these four C14H8 products.