Photoreactions of aromatic compounds—XVIII : Photoinduced aromatic substitution in liquid ammonia, ammonia/methanol and ammonia/watert

Abstract

m-Nitroanisole and some substituted m-methoxynitrobenzenes upon illumination in liquid ammonia, ammonia/methanol or ammonia/water undergo substitution of the m-OMe group by the amino group—a reaction possibly starting from the lowest π,π* singlet and comparable with the photohydrolysis of these compounds. Nitrobenzene, the dinitrobenzenes and chloronitrobenzenes on photoreaction in liquid ammonia are substituted at the para/ortho and not at the meta position. Nitrobenzene upon irradiation in liquid ammonia yields two unstable photoproducts ; a substance with an absorption maximum at 335 nm, which does not seem to be an intermediate in the formation of the stable product p-nitroaniline: and the nitrobenzene radical anion which may be an intermediate. Excited singlet and triplet states appear both to function as starting levels for the animation of nitrobenzene.