Nucleophilic substitution is a fundamental reaction in organic chemistry where an electron-rich nucleophile replaces a leaving group in a molecule. This type of reaction is commonly used in the synthesis of organic compounds, such as pharmaceuticals and materials. Nucleophilic substitution can occur through various mechanisms, such as SN1 (substitution nucleophilic unimolecular) and SN2 (substitution nucleophilic bimolecular), depending on the reactivity of the substrate and nucleophile involved. Research in nucleophilic substitution focuses on understanding the factors that influence reaction rates, regioselectivity, and stereoselectivity, as well as developing new methodologies for efficient and selective substitutions.