Reaction of azide radicals with aromatic compounds. Azide as a selective oxidant
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In basic aqueous solution the N/sub 3/.radical is found to oxidize aromatic systems such as aniline and phenoxide ions and their derivatives at rate constants of (3-5) x 10/sup 9/ M/sup -1/s/sup -1/. In contrast to the reactions of OH radicals, where addition to the ring dominates, oxidation appears to be directly by electron transfer. Compounds such as benzene, toluene, and anisole are not observably oxidized by N/sub 3/. Phenol, in its neutral form in acidic solution, is oxidized several orders of magnitude more slowly than is the phenoxide anion. The rate of oxidation of phenols is strongly dependent on substitution, with activating groups increasing the rate in the order para > ortho > meta. N/sub 3/. can be readily prepared radiolytically by OH oxidation of azide. Being a neutral radical which does not absorb significantly above 300 nm it is very promising as a selective oxidant for pulse radiolysis studies. 27 references, 6 figures, 3 tables.