Electrophilic and nucleophilic reagents

Electrophilic reagents are chemical species which, in the course of chemical reactions, acquire electrons, or a share in electrons, from other molecules or ions. Although this definition embraces all oxidizing agents and all Lewis acids, electrophilic reagents are ordinarily thought of as cationic species, such as H⁺, NO₂⁺, Br⁺, or SO₃ (or carriers of these species such as HCl, CH₃COONO₂, or Br₂), which can form stable covalent bonds with carbon atoms. Electrophilic reagents frequently are positively charged ions (cations). See also Acid and base.

Nucleophilic reagents are the opposite of electrophilic reagents. Nucleophilic reagents give up electrons, or a share in electrons, to other molecules or ions in the course of chemical reactions. Nucleophilic reagents frequently are negatively charged ions (anions). Typical nucleophilic reagents are hydroxide ion (OH⁻), halide ions (F⁻, Cl⁻, Br⁻, and I⁻), cyanide ion (CN⁻), ammonia (NH₃), amines, alkoxide ions (such as CH₃O⁻), and mercaptide ions (such as C₆H₅S⁻). See also Substitution reaction.