Ketones hydroxy aromatic, iodination

A computational study of the reaction of benzene and other arenes with bromine indicates the inherent competition between substitution and addition processes, and shows that both, 2-cis and 1,4-syn additions may compete with the classical substitution pathway involving Wheland intermediates. The bromination of the dipyrromethene dye (3) has been found to occur in a stepwise manner in the order 2,6- followed by 3,5- and Anally 1,7-positions. There have been kinetic and mechanistic studies of the bromination of sulfanilic acid using A-bromosuccinimide and of salicyclic acid with bromine. The kinetics of the iodination of substituted hydroxy aromatic ketones using iodine and iodic acid have also been reported. " ... 

The fluorescence efficiencies of aromatic molecules are reduced by heavy atom substituents such as bromine and iodine and by certain other groups such as aldehyde and keto as well as nitro groups. However, in many cases the substituents that decrease the intensity of fluorescence enhance the intensity of phosphorescence. Consequently, aromatic nitro compounds, bromo- and iodo-derivatives, aldehydes, ketones, and some A-heterocyclics tend to fluoresce very weakly or not at all. However, most of them phosphoresce quite intensely. On the other hand, many substituents that are electron donors such as amino, hydroxy, and methoxy often tend to increase the quantum yields of fluorescence of molecules to which they are attached. 

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