Carbon-13 chemical shifts are reported for a series of carcinogenically active and related inactive polynuclear hydrocarbons. Resonance assignments for complex systems such as 3-methylcholanthrene, dibenzanthracenes, benz[a]anthracene and its 7-methyl and 7,12-dimethyl derivative, have been made primarily from a study of simpler models, including phenanthrene, triphenylene, and anthracene. Selective proton decoupling has been employed extensively. Quaternary carbon assignments have been aided by deuterium isotope shift and spin–lattice relaxation time measurements. Vicinal C—D couplings have been found to be unreliable as means of assignment for quaternary carbons.
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Ozubko et al. (1974) studied this question.