THE PHOTOCHEMICAL REACTION OF CERIUM(IV) AMMONIUM NITRATE WITH ALKENES. RATE AND MECHANISM FOR THE ADDITION OF THE NITRATE RADICAL TO ALKENES

Article abstract of DOI:10.1016/S0040-4020(01)90103-6

The photochemical reaction of cerium(IV) ammonium nitrate (CAN) in acetonitrile with cyclohexene, 1-octene and a series of styrene derivatives leads to the formation of 1,2-dinitrate adducts in high yields.The reaction takes place by the intermediacy of the nitrate radical which forms in the photolysis of CAN.The reaction rate of NO3^. with the olefinic substrates has been determined by the laser flash photolysis technique.High values of reactiviy are observed, the second order rate constants ranging from 5E8 to 9E9 1/M*s.The plot of the rate data for substituted styrenes against Σ⁺ values is linear and affords a ρ value of -0.97.It has also been found that the kinetic data fit in with the Rehm-Weller equation for electron transfer processes, thus suggesting that the transfer of an electron from the substrate to the attacking radical is the first (and rate determining) step in the reaction of styrene derivatives with NO3^..This suggestion is also supported by the observation that trans-β-methylstyrene is more reactive than α-methylstyrene, in line with the easier oxidizability of the former substrate and in contrast with what is observed in free radical additions.Kinetic data for 1-octene and cyclohexene do not fit the Rehm-Weller plot and the mechanistic attribution to the reaction of these substrates with nitrate radical is uncertain.