Photochemical production of the electrophilic cyano-radical: homolytic aromatic cyanation

The reaction of cyano-radicals, produced by the photolysis of cyanogen iodide, with aromatic compounds afforded aromatic nitriles. The isomer ratios and the relative reactivities were determined for a variety of monosubstituted benzenes and the results indicated that the cyano-radical preferably attacks relatively electronegative sites. The partial rate factors for the meta- and para-positions correlate with σ+ to give a slope of –0·42. It is concluded that cyano-radical possesses a slight electrophilic character.