ELECTROPHILIC BROMINATION OF CARBON-CARBON DOUBLE-BONDS - STRUCTURE, SOLVENT AND MECHANISM

This chapter discusses the experimental conditions, under which it is possible to obtain data relevant to the study of the bromination mechanism, and presents the evidence for the occurrence of charge transfer complexes and cationic intermediates on the reaction pathway. The chapter presents the kinetic substituent and solvent effects on this cation-forming halogenation; these effects are discussed in terms of kinetic selectivity, transition-state shifts and solvation. From an energetic point of view, free bromine addition can be considered as an ionization process leading from a neutral reagent to a cation-anion pair in a single elementary step, most work on this electrophilic addition can be used to understand how charge separation and stabilization occur in the organic reactions. Bromination thus appears as a suitable model, and is complementary to the conventional heterolytic substitutions. The association of kinetics and stereochemistry is particularly useful for obtaining data on the structure, open or bridged depending on the substituents of bromination intermediates. © 1993, Academic Press Limited.