Unstable intermediates. Part CIII. Electron spin resonance studies of γ-irradiated malonamide and related compounds
Previous workers have presented strong evidence in favour of the formation of radicals of type RCONH in γ-irradiated malonamide and (cyanoacetyl)urea. The e.s.r. spectra assigned to these radicals are characterised by a double splitting of about 80 G, and largely on the basis of this coupling, which was assigned to the NH proton, a σ-structure was postulated. This assignment is questioned particularly because the 14N hyperfine tensor is characteristic of π-radicals. Comparison of single-crystal and powder spectra from irradiated malonamide with those from solids known to contain NH3+ radicals, shows that this species is a possible alternative. Results for cyanoacetylurea rule out this assignment, but the data fit well with expectation for radicals of the type R(H)CN.