In organic chemistry, a nucleophilic addition reaction is an addition reaction where a chemical compound with an electron-deficient or electrophilic double or triple bond, a π bond, reacts with electron-rich reactant, termed a nucleophile, with disappearance of the double bond and creation of two new single, or σ, bonds. The reactions are involved in the biological synthesis of compounds in the metabolism of every living organism, and are used by chemists in academia and industries such as pharma to prepare most new complex organic chemicals, and so are central to organic chemistry. Addition reactions require the presence of groups with multiple bonds in the electrophile: carbon–heteroatom multiple bonds as in carbonyls, imines, and nitriles, or carbon–carbon double or triple bonds.