Electrofili

Electrofili, in English electrophiles, are electron-deficient species in chemistry that seek electron density from nucleophiles. They accept electron pairs to form new covalent bonds, and in Lewis acid–base terms an electrophile is a Lewis acid—an electron pair acceptor.

Electrofili can be positively charged, such as protons (H+), carbocations (R3C+), or other metal-centered cations, or neutral but highly polarizable entities, such as the carbonyl carbon of aldehydes and ketones or certain halogen-containing species. Their reactivity depends on the availability of an accepting orbital and the stability of the developing bond, influenced by solvent, temperature, and substituents.

Common examples include H+, alkyl halides (R–X) in substitution reactions, carbocations formed in situ, and carbonyl compounds where the carbonyl carbon is attacked by nucleophiles. Electrofili are often generated or activated by Lewis acids such as AlCl3, FeCl3, or BF3, which increase the positive character of a center and facilitate bond formation.

Typical reaction types involve electron flow from a nucleophile to an electrophile: electrophilic aromatic substitution, electrophilic addition to alkenes (for example, protonation or halogenation), and nucleophilic substitutions (SN1, SN2) where the substrate functions as the electrophile. Electrophilic intermediates such as carbocations also appear in rearrangements and polymerization processes.

Hard and soft electrophiles, described by HSAB theory, influence selectivity by preferring different nucleophiles. Electrofili are central to many chemical processes, enabling bond formation, functionalization, and material synthesis. See also electrophile, nucleophile, Lewis acid, electrophilic aromatic substitution.