Rückstoßbromierung aromatischer Verbindungen

In the neutron irradiation of bromobenzene in a mixture with other halogene benzenes, a non statistical distribution for the formation of position isomeric $^{82}$Br-labelled dibromo- and bromohalogene benzenes was observed. For the elucidation of the reaction mechanism, toluene, which acts as a scavenger for the predominantly formed radicalic bromine, was added to the irradiation samples. Under the conditions mentioned, brominations occuring in the aromatic nucleus must have taken place by an electrophilic substitution. The non statistical formation of the position isomeric radioactive labelled compounds is due to different activation entropies of the reactive positions in the molecule. They, on the other hand, may be reflected by action ofpolarisation and polarisability effects