Molecular-Orbital Treatment of Isotropic Hyperfine Interactions in Simple Aliphatic Radicals

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Abstract
The problem of isotropic hyperfineinteractions in the EPRspectra of aliphatic free radicals is approached from the molecular‐orbital picture of hyperconjugation. The ethyl, methylethyl, and 1,1‐dimethylethyl radicals are treated by this approximation; with a reasonable choice of parameters, the results can be correlated rather well with our present knowledge of aliphatic radicals. The calculated coupling constants of methyl group hydrogens are of the order of 15 to 25 gauss, do not decrease radically with the presence of additional methyl groups, and are very nearly proportional to the molecular‐orbital unpaired electron density at the central carbon atom.