POLAR RADICALS .3. A CASE AGAINST ANCHIMERIC ASSISTANCE IN BROMINATION OF 1-BROMOBUTANE

The photoinitiated bromination of 1-bromobutane with molecular bromine has been reinvestigated. The product distribution obtained at the completion of the reaction was found to be the result of the equilibration of the alkyl radicals which were initially produced by hydrogen abstraction. The alkyl radicals were shown to equilibrate with the hydrogen bromide produced in the reaction, changing the product distribution from that predicted by “normal” polar effects to one which showed an abnormally high yield of 1,2-dibromobutane. The experimental observations clearly rule out participation by a neighboring bromine atom in the rate-determining abstraction step in the halogenation of bromoalkanes. These results are discussed in light of the general problem of bridged bromine intermediates. © 1969, American Chemical Society. All rights reserved.