Photodegradation of Some Alkyl N-Arylcarbamates

Article abstract of DOI:10.1021/jo01299a031

The UV photodegradation of a number of alkyl N-arylcarbamates in solution has been investigated.A mechanism for the photodegradation process is proposed.The initial excitation of the carbamate moiety involves a ?,?(excited) transition into an excited singlet state.Chemical change from this excited state proceeds primarily via homolytic cleavage of the nitrogen to alkoxycarbonyl bond to provide a radical pair in a solvent cage.The quantum efficiency for carbamate disappearance is low.The major indentifiable products are amines and photo-Fries rearrangement products (where formation is possible).The arylaminyl radical is proposed as a major reaction intermediate.It is suggested that the failure for the sum of quantum yields of formation for degradation products (amines and photo-Fries rearrangement products) to coincide with quantum yields for carbamate disappearance is due to reactions (e.g., coupling) of the aminyl radicals.The quantum yield for carbamate disappearance is independent of both methyl group substitution on the phenyl ring and excitation wavelength.In contrast, the quantum yield for the disappearance of the parent arylamine, a carbamate photodegradation product, does show dependence on these factors.