Reactions with Aromatic Compounds of Recoiling Bromine Atoms Formed from the ^76,77Kr –* ^76,77Br Transformations. Liquid-Phase Reactions

Bromine atoms produced via the ⁷⁶Kr(EC)⁷⁶Br and ⁷⁷Kr(β⁺/EC)⁷⁷Br transformations were reacted with simple benzenoid compounds in the liquid phase. For both ⁷⁶Kr and ⁷⁷Kr, bromodeprotonation resulted in a reactivity constant p+⋍ -0.6, with higher yields for ⁷⁶Br. Whereas bromodeprotonation was hypothesized to occur via formation of a product-determining σ-complex by radical bromine species, ipso substitution was described in terms of a two-step addition-elimination mechanism in which bond breakage is product determining. While radical bromine species are probably involved in substituent displacements from monosubstituted arenes, polysubstituted aromatic compounds activated to nucleophilic attack were shown to involve an additional nucleophilic reaction pathway.