Chapter 9 The electrophilicity index in organic chemistry

We review in this chapter the applications of theoretical scales of global and local electrophilicity to rationalize the reactivity and selectivity for a significant number of reactions in organic chemistry. The model is based on the global electrophilicity index, formerly introduced by Maynard et al. and further formalized by Parr et al. The global electrophilicity index categorizes, within a unique absolute scale, the propensity of electron acceptors to acquire additional electronic charge from the environment. The local extension of this index provides useful information about the active sites of electrophiles, thereby allowing the characterization of the intramolecular selectivity in these systems. These concepts will be illustrated for a series of chemical reactions in organic chemistry, including polar cycloadditions and electrophilic addition reactions, substrate selectivity in electrophilic aromatic substitution (Friedel-Crafts) reactions, hydrolysis of carbonyl compounds, the reactivity of carbenes and carbenium ions and the superelectrophilicity of dicarbenium, oxonium and dicarboxylic acids.