Photochemical Behaviour of Carbamates Structurally Related to Herbicides in Aqueous Media: Nucleophilic Solvent Trapping versus Radical Reactions

Abstract

Irradiation of N-aryl O-aryl carbamates has been carried out in H2O/CH3CN (1 : 1 v/v) solutions at λ>290 nm. When chlorine is on the N-aryl ring, halogen-substituted products are found. These photoproducts derive from the trapping of the intermediate radical cation by water and, even, by acetonitrile leading to phenols and N-arylacetamides (photo-Ritter products), respectively. Unsubstituted N-aryl carbamates slowly undergo photo-Fries reaction.