Elektrofili

Elektrofili, or electrophiles, are chemical species that accept electron pairs from nucleophiles during chemical reactions. In Lewis theory they are Lewis acids, typically electron-poor or positively charged, and are attracted to electron-rich sites in other molecules. Electrofili can be neutral yet electron-deficient or positively charged ions such as protons or nitronium ions. Common examples include H+, carbocation species, NO2+, acylium ions (RCO+), and certain Lewis acids like boron trifluoride (BF3) or aluminum chloride (AlCl3).

Electrofili react by accepting electron density from nucleophiles, forming new covalent bonds. The most familiar contexts are electrophilic addition to carbon–carbon double bonds (alkenes) and electrophilic aromatic substitution on benzene rings, where the electrophile temporarily forms a sigma complex before deprotonation restores aromaticity. In SN1-type reactions, the substrate often acts as the electrophile, losing a leaving group to generate a carbocation that is subsequently attacked by a nucleophile.

In organic synthesis, controlling electrophilicity enables a range of functionalizations, such as nitration with nitronium ion NO2+, acylation via acylium ions in Friedel–Crafts reactions, and halogenation using activated halogen species. Factors that influence electrophilicity include substituents that withdraw electron density, solvent effects, and the hard–soft acid–base concept, which helps predict which nucleophiles will pair with a given electrophile. Overall, the concept of elektrofili is central to understanding how many common organic transformations proceed.