elektrofilik

Elektrofilik, or electrophilic in English, describes the property of a chemical species that seeks to accept electron density from a nucleophile during a reaction. An electrophile is typically electron-poor and bears a positive charge or a highly polarized atom, making it capable of forming a bond by accepting an electron pair.

Common electrophiles include protons (H+), carbocations, and electron-poor species such as boron trifluoride (BF3), sulfur trioxide (SO3), and the nitronium ion (NO2+). In many organic reactions, electrophiles react with nucleophiles such as alkenes, arenes, or carbonyl compounds. The interaction often proceeds via electrophilic addition or electrophilic aromatic substitution, processes in which the electrophile attaches to an electron-rich site and is followed by further steps that restore stable bonding.

Mechanistically, electrophilicity drives the rate-determining steps of these reactions. In electrophilic addition to alkenes, the pi bond donates electron density to the electrophile, forming a new bond and frequently generating a carbocation intermediate that is trapped by a nucleophile or deprotonated. In electrophilic aromatic substitution, the aromatic ring donates electron density to the electrophile, forming a non-aromatic intermediate that is subsequently rearomatized.

Factors influencing electrophilicity include the presence of Lewis acids that increase the positive character of the electrophile, solvent polarity, temperature, and substituents that stabilize developing charge. Electrophilicity can be assessed theoretically using indices such as the electrophilicity index or by related parameters like LUMO energy and acceptor numbers, which correlate with reaction rates and selectivity. Electrophiles are central to many synthetic strategies, including halogenation, nitration, sulfonation, and other functionalization reactions, but they can be highly reactive and require careful handling.