Chemically Induced Dynamic Nuclear Polarization

Abstract

Alkyl radicals are generated by reactions of phenyl radicals in binary mixtures of substituted alkanes. CIDNP-NMR spectra of their reaction products are explained by S - T 0 -transitions in radical pairs formed in free radical encounters. From comparisons of calculated and observed CIDNP spectra the (g-factor and the proton hyperfine coupling constant of · CHCl 2 are determined [g = 2.0080 ± 0.0003, a = (- 17.0 ± 1.0) G]. The inclusion of nuclear relaxation in free radicals in quantitative CIDNP treatments is discussed, and evidence for the radical pair mechanism causing CIDNP of phenyl derivatives during dibenzoylperoxide decompositions is presented.