Relation between the Proton Hyperfine Interaction and the C13–H1 Spin-Spin Coupling in Free Radicals

Abstract

It is shown that the C¹³–H¹ spin‐spin coupling constant J(C¹³–H¹) and the proton hyperfine constant Q(H¹) in a free radical can be considered as interdependent, and that they both can be estimated by calculating the perturbation produced in the electronic wave functions by the magnetic moment of the proton. For a C–H fragment with an unpaired π electron on the carbon atom an approximate relation is established between Q(H¹) and J(C¹³–H¹). Using the experimental value of J(C¹³–H¹) for the benzene molecule, Q(H¹) is found to have a negative sign and order of magnitude agreement with experiment.