The Presence of Two Reactive Intermediates in the Photolysis of N-Bromosuccinimide: Kinetic Proofs

Article abstract of DOI:10.1021/jo00264a005

The direct photolysis of N-bromosuccinimide in the presence of an olefin (to scavenge bromine and its atoms) was shown to products the ring-opened product β-bromopropionamide from two reactive intermediates as confirmed by kinetic analysis of competing reactions of the ring opening and addition to benzene.The reactive intermediates were assigned to the succinimidyl radical and the precursor in agreement with the previous publication.The plots of relative quantum efficiencies of β-bromopropionamide against benzene concentrations were shown to be consistent with mathematical predictions derived from the proposed reaction scheme.These established that while both the precursor and succinimidyl radical underwent the ring-openning reaction, only the latter showed the reactivity of attacking benzene.The precursor can be either another state of the succinimidyl radical or an excited state of NBS; evidence to distinguish between these is not available.It is surmised that failure to recognize the presence of the precursor in the direct photolysis of N-bromosuccinimide has contributed to the protracted controversy in the current literatures.