Electrophilic Substitution of Heteroaromatic Compounds with Six-Membered Rings

The limited amount of quantitative data available on the electrophilic substitution of heterocycles is surveyed. Initial objectives are first to determine the species undergoing substitution and then to find out the amount by which the heterocyclic atom or group activates or deactivates the ring by comparison with the corresponding benzenoid compound. When sufficient data are available it is hoped to correlate this by means of a Hammett-type treatment or by MO methods.