Additioreaktio

Additioreaktio is a term used in chemistry to describe a class of reactions in which two molecules add together to form a single product, typically by addition across a multiple bond such as a carbon–carbon double bond. In organic chemistry, activation occurs when an unsaturated substrate reacts with a reagent that supplies atoms to the pi bond, converting it into a saturated single bond.

Common types include electrophilic additions, where an electron-deficient species adds to alkenes or alkynes (for example, hydration to give alcohols, hydrohalogenation to give alkyl halides, and halogenation to give vicinal dihalides). Radical additions also occur, such as anti-Markovnikov hydrohalogenation and radical additions of HBr to alkenes. Hydrogenation is a prominent example, where H2 adds across a double bond in the presence of a metal catalyst.

Stereochemistry varies by mechanism: halogenation typically proceeds with anti addition; hydrogenation proceeds in a syn fashion on many catalysts. Regioselectivity such as Markovnikov or anti-Markovnikov outcomes arises from the mechanism and catalysts; peroxide-initiated hydrohalogenation can invert the usual regiochemistry.

Applications include the preparation of alcohols, alkyl halides, and polymers via addition polymerization of alkenes. Understanding additioreaktio is fundamental in organic synthesis and industrial chemistry, contributing to the design of routes to fine chemicals and materials.

See also: addition reaction, electrophilic addition, radical addition, hydrohalogenation, hydration, polymerization.