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Mechanism of tritium-atom-promoted isotope exchange in the benzene ring: application to tritium labeling of biologically important aryl compounds

Journal Article · · J. Phys. Chem.; (United States)
DOI:https://doi.org/10.1021/j150669a043· OSTI ID:6120955
Reaction of thermal tritium atoms, generated by microwave activation of T/sub 2/ gas, with benzene and biphenyl was studied at approx. -50 and -196/sup 0/C. The saturation reactions (i.e., benzene ..-->.. cyclohexane-t/sub 6/) predominated over isotope exchange (i.e. benzene ..-->.. benzene-t) at-196/sup 0/C. However, significant exchange labeling occurred at approx. -50/sup 0/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/sup 0/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 benzene or cyclohexane, whereas it could not be labeled otherwise.
Research Organization:
Univ. of California, Berkeley
DOE Contract Number:
AC03-76SF00098
OSTI ID:
6120955
Journal Information:
J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 88:25; ISSN JPCHA
Country of Publication:
United States
Language:
English