Alkylaatioon

Alkylaatioon, commonly written as alkylation in English, is a chemical reaction in which an alkyl group (R–) is transferred to a substrate. The process increases the carbon framework of the target and can target carbon, nitrogen, oxygen, or sulfur sites. Alkylation is widely used in organic synthesis, petrochemistry, and biochemistry to modify reactivity, introduce side chains, or build more complex molecules.

Two broad classes of mechanisms are involved. In nucleophilic alkylation, a nucleophile attacks an electrophilic alkyl partner, often with loss of a leaving group (SN2 or SN1 pathways). In electrophilic alkylation, an electrophilic alkylating agent transfers an alkyl group to an nucleophilic ring or atom, as seen in Friedel–Crafts-type alkylations of arenes under strong acid or Lewis acid catalysis. O- or N-alkylation refers to alkyl groups added to oxygen or nitrogen centers, respectively, and can be driven by similar catalysts or reagents.

Industrial and practical relevance is broad. In petroleum refining, alkylation combines light olefins with isobutane under acidic catalysis to produce high-octane alkylates for gasoline. In organic synthesis and pharmaceuticals, alkylation is used to append alkyl chains to nucleophiles, to protect or modify functional groups, and to influence pharmacokinetic properties. Selectivity challenges include regio- and stereochemistry, as well as unwanted polyalkylation or rearrangements in some substrates. Due to the variety of alkylating agents, many alkylation processes require careful control of catalysts, temperature, and reaction conditions to achieve the desired product while minimizing side reactions and safety risks.