SOLVENT-INDUCED SCISSION OF DIARYLMETHANES IN DIHYDROARENE DONOR SOLVENTS - AN EXPERIMENTAL AND MECHANISTIC MODELING STUDY OF HYDROGEN-TRANSFER PATHWAYS

Mechanistic kinetic models derived from thermochemical. data were utilized to quantify the hydrogen-transfer pathways involved in the scission of benzylarene (PhCH(2)-Ar) carbon-carbon bonds in a series of dihydroarene/arene solvent mixtures. The model predicts that free hydrogen atoms (HA) play a dominant role in promoting the scission of strong benzylarene carbon-carbon bonds in both 9,10-dihydrophenanthrene solvent mixtures and cyclic olefins. In 9,10-dihydroanthracene solvent mixtures, the direct transfer of a hydrogen from the dihydroarene to the benzylarene by the reverse radical diproportionation (RRD) pathway is more important than free hydrogen atoms when no diluent is present. We demonstrate the utility of our empirically derived hydrogen-transfer model by comparing the predicted selectivity to the experimental measured selectivity of 2-methylnaphthalene/1-methylnaphthalene (2MN/1MN) in the thermolysis of 1,2'-dinaphthylmethane (1,2'-DNM) in anthracene/9,10-dihydroanthracene (An/AnH(2)) solvent mixtures. Our model shows that a change in the hydrogen-transfer pathway from RRD to HA explains the experimentally observed selectivity of BMN/1MN in An/AnH(2) solvent mixtures.