ESR Studies of Naphthoquinones and Related Compounds. Hyperfine Interaction by the Methoxyl Group as a Conformational Probe

ESR spectra were run on a large number of methoxy-substituted para-semiquinones. With the help of MO calculations it was deduced that methoxyl hyperfine interaction in these systems is, in part, a function of the spin density on the ether oxygen. By the use of model compounds it was further deduced that only one conformational isomer is effective in giving rise to splitting. A semiempirical value for |QOCH3| was calculated to be 5.6 G.