Friedel-Crafts alkylation

The Friedel-Crafts alkylation is a name reaction in organic chemistry. It is used to add alkyl groups to aromatic rings using a Lewis acid like aluminium chloride as a catalyst.

 Materials 
The Friedel-Crafts alkylation starts with an aromatic compound like benzene () and an alkyl halide like ethyl chloride (). A small amount of a Lewis acid, usually aluminium chloride, is added to be a catalyst.

Alkenes can be used in place of alkyl halides by using a Brønsted acid as the catalyst. This version of the reaction is common in the chemical industry.

 Mechanism 
The Friedel-Crafts alkylation is a type of electrophilic aromatic substitution with two carbocation intermediates. First, the alkyl halide reacts with the catalyst, making a carbocation and an anionic Lewis adduct:

If starting from an alkene and Brønsted acid, the carbocation is instead made from protonation of the alkene:

The carbocation is a strong electrophile, so it is attracted to the many electrons in the aromatic ring. The carbocation reacts with the ring, making a new covalent bond between carbon atoms to form a larger arenium intermediate,

Finally, the adduct abstracts a hydrogen ion from the larger carbocation, which regenerates the catalyst and releases the hydrogen halide byproduct:

The net reaction is

 References 

Category:Name reactions