elektrophil

Elektrophil is the term used in German-language chemistry for what is generally called an electrophile in English. It describes a chemical species that seeks electrons and accepts an electron pair from a nucleophile during a reaction. In Lewis acid–base theory, an Elektrophil acts as a Lewis acid, accepting an electron pair from a Lewis base.

Electrophiles are typically electron-poor and may be positively charged or highly electron-deficient. They react with nucleophiles, which donate electron pairs to form covalent bonds. Common examples include protons (H+), carbocation intermediates, and neutral Lewis acids such as aluminum chloride (AlCl3), iron(III) chloride (FeCl3), and boron trifluoride (BF3). Carbonyl-derived species that can generate acylium ions (R–CO+) also behave as electrophiles in appropriate conditions.

Electrophiles participate in several fundamental reaction classes. In electrophilic addition, an alkene or alkyne adds to an electrophile to yield a new covalent bond and often an intermediate carbocation. In electrophilic aromatic substitution, an electrophile attacks an activated aromatic ring, leading to substitution for a hydrogen atom. Electrophiles also enable Friedel–Crafts acylation and alkylation, halogenation in the presence of catalysts, and the formation of various functional groups.

Hard and soft electrophiles, concepts from HSAB theory, describe preferences for reaction partners of corresponding hardness or softness. Quantitative measures of electrophilicity exist, such as Mayr’s electrophilicity scale and related computational indices, though practical use often depends on the specific substrate, solvent, and conditions.

Safety and handling depend on the reagent; many electrophiles are reactive, corrosive, or toxic, and require appropriate precautions.