The photosensitised oxidation of amines. Part I. The use of benzophenone as a sensitiser

Abstract

Product studies are reported on the benzophenone-sensitised photo-oxidation of primary, secondary, and tertiary aliphatic amines and N-alkylanilines. Aliphatic amines gave aldehydes and imines, whereas N-alkylanilines were dealkylated but did not give imines. Amines which are known physical quenchers of singlet oxygen were efficiently oxidised. The reactivity of these compounds, and the type of products formed in the reaction, are explainable in terms of a mechanism in which hydrogen atom abstraction from the amine by triplet ketone is the primary chemical reaction. The results are not in accord with the participation of singlet oxygen. Quantum yield measurements of oxygen uptake, amine disappearance, and product formation are consistent with the proposed mechanism.