Elektrofilai

Elektrofilai, commonly called electrophiles in English, are chemical species that seek electron density and act as electron pair acceptors in reactions. They are typically Lewis acids, meaning they accept electrons from nucleophiles during bond formation. Electrophiles are often positively charged or highly polarized, making them susceptible to attack by nucleophiles such as carbon- or heteroatom-centered lone pairs.

Common examples of electrophiles include protons (H+), nitronium ion (NO2+), halonium ions, carbocations, acylium ions, boron trifluoride (BF3), aluminum chloride (AlCl3), and sulfur trioxide (SO3). Many organic reactions proceed via electrophiles generated in situ, such as acetyl cations in Friedel–Crafts acylation or protonated alkenes in electrophilic additions to double bonds.

Electrophiles are often discussed in the hard and soft acid–base (HSAB) framework. Hard electrophiles prefer hard nucleophiles, and soft electrophiles prefer soft nucleophiles, influencing reaction rates and selectivity. In organic synthesis, electrophiles participate in several key reaction types, including electrophilic addition to alkenes (e.g., H+ or X+ adding to a carbon–carbon multiple bond) and electrophilic aromatic substitution, where an electron-rich aromatic ring reacts with an electrophile to form a substituted product.

The concept is central to many industrial and laboratory processes, including nitration, sulfonation, and various acylation and alkylation methods. The term elektrofilai derives from roots meaning “electron-loving,” reflecting their tendency to accept electron pairs during chemical bonding.