Alkylointi

Alkylointi, commonly translated as alkylation, refers to a family of chemical reactions in which an alkyl group is introduced into a molecule. The process is fundamental in organic synthesis and in refining chemistry, enabling the construction of new carbon–carbon bonds and substitution at heteroatoms. Alkylation can be classified by mechanism and by the nature of the substrate being alkylated.

Two broad classes exist: electrophilic and nucleophilic alkylation. Electrophilic alkylation generates a positively charged alkyl species that attacks an electron-rich center, as in Friedel–Crafts alkylation of arenes with alkyl halides in the presence of a Lewis acid. This route often gives rearrangements and polyalkylation.

Nucleophilic alkylation involves a nucleophile substituting a leaving group on an alkyl electrophile, typically via SN2 or, for hindered centers, SN1 mechanisms. Common nucleophiles include enolates, amines, alkoxides, and thiolates; common electrophiles are primary, secondary or benzylic alkyl halides or sulfonates. Regio- and chemoselectivity depend on substrate and conditions; O- and N-alkylation are common competing pathways.

In industry, alkylation is used to produce high-octane fuels and to assemble complex synthetic targets. A well-known example is the alkylation of isobutane with olefins to yield alkylate gasoline in refinery units using strong acids as catalysts.

Alkylating agents are often hazardous, with many capable of transferring alkyl groups to biomolecules; handling requires appropriate controls and regulatory compliance.