Kinetic Isotope Effects in Hydrogen Atom Transfer Reactions between Benzylic Carbons

Article abstract of DOI:10.1021/jo00351a003

The kinetic deuterium isotope effect for transfer of hydrogen from tetralin, dihydroanthracene, fluorene, diphenylmethane, triphenylmethane, and acenaphthene to the benzyl radical was measured at 170 deg C.The range of values for the effect was from 6.5 to 8.0.Activation energy parameters were obtained for five of the hydrogen donors.The apparent difference between activation energies for deuterium or hydrogen transfer was <*> 2 kcal/mol for triphenylmethane, diphenylmethane, and tetralin.Applications of several tests indicate that a tunnel effect plays a significant role in these hydrogen transfers.