Electron resonance spectra of some radicals derived from acetylenes and nitriles

The electron resonance spectra of a series of radicals derived by hydrogen abstraction from substrates containing carbon-carbon or carbon-nitrogen triple bonds have been studied in fluid solutions. The radicals ·CH2CN, ·CH2C ≡ CH and ·CH2C ≡ C·CH3 which have a linear heavy-atom framework show interesting temperature dependent line-width variations. These are attributed to spin-rotational interactions arising from anisotropic molecular reorientation. It is suggested that the motion about the long axis of these radicals is inertial in character. The equilibrium geometries and hyperfine coupling constants of the propargyl and cyanomethyl radicals have been estimated from INDO-LCAO-SCF calculations.