The electronic structure of chichibabin's hydrocarbon

Abstract

ESR spectra have been measured of the triplet state of Chichibabin's hydrocarbon. The molecules were 13C-labeled at the central carbon atoms and substituted with tertiary butyl groups to eliminate dimerization and other side-reactions. It is found that each unpaired electron interacts predominantly with only one triphenyl methyl moiety. An upper limit to the exchange integral is 7 × 10 7 Hz, whereas MO calculations predict a value orders of magnitude larger. This discrepancy, the so-called biradical paradox, is attributed to the crudeness of the calculations.