Photochemistry of N-alkylsuccinimide in methanol and ethanol: An experimental and calculated investigation

The photochemistry of N-R-succinimide (R = H, Me, Et) in methanol and ethanol was investigated. Two kinds of photo-reduction products, i.e. 5-alkoxy-N-R-2-pyrrolidinone (2) and 5-(1-hydroxyalkyl)-5-alkoxy-N-R-2-pyrrolidinone (3) (alkoxy: MeO and EtO, R: Me and Et) have been identified. The formation of 2 relates to a continuous two-step H-abstraction, which is rare in the photolysis of common ketones. However, in the case of succinimide, a new pinacolic product, 5,5′-dihydroxy-5,5′-bis(2-pyrrolidinone) (4), was found for the first time. DFT calculations have been carried out in order to study the aggregation behaviors of succinimide during the photochemical process. The strong tendency to form succinimide dimer (1c–1c) via reciprocal intermolecular hydrogen-bonds is in good explanation for the generation of product 4.