This lecture covers the reactivity of aromatic compounds, focusing on electrophilic addition and substitution reactions. It explains how multiple bonds in aromatic systems differ from olefins, the mechanism of electrophilic aromatic substitutions, regioselectivity, and examples of reactions such as bromination, Friedel-Crafts alkylation, and sulfonation. The lecture also discusses regioselectivity in electrophilic substitutions directed by previous substituents and the learning outcomes related to the weak nucleophilic nature of aromatic systems.