Mechanism of Tritium-Atom-Promoted Isotope Exchange in the Benzene Ring: Application to Tritium Labeling of Biologically Important Aryl Compounds

Article abstract of DOI:10.1021/j150669a043

Reaction of thermal tritium atoms, generated by microwave activation os T₂ gas, with benzene and biphenyl was studies at ca.-50 and -196 deg C.The saturation reactions (i.e.,benzene->cyclohexane-t₆)predominated over isotope exchange (i.e.,benzene->benzene-t( at -196 deg C.However, significant exchange labeling occurred at ca.-50 deg C, with a concomitant reduction in the yields of saturated products.This reversal in labeled product yields at the different temperatures is due, in part, to the faster rate of H expulsion from the intermediate cyclohexadienyl radical at -50 deg C and to the increased mobility of the warmer matrix that retards multiple T- reactions with the same aryl molecule by covering up singly tritiated intermediates.The less volatile aryl compound, biphenyl, was labeled in a diffusionally active matrix of either benezene or cyclohexane, whereas it could not be labeled otherwise.