The Friedel–Crafts reactions are a set of reactions

Organic reaction

Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, photochemical reactions and redox reactions. In organic synthesis,...

 developed by Charles Friedel

Charles Friedel

Charles Friedel was a French chemist and mineralogist. A native of Strasbourg, France, he was a student of Louis Pasteur at the Sorbonne...

 and James Crafts

James Crafts

James Mason Crafts was an American chemist, best known for developing the Friedel-Crafts alkylation and acylation reactions with Charles Friedel in 1876.-Biography:...

 in 1877. There are two main types of Friedel–Crafts reactions: alkylation

Alkylation

Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbene . Alkylating agents are widely used in chemistry because the alkyl group is probably the most common group encountered in...

 reactions and acylation

Acylation

In chemistry, acylation is the process of adding an acyl group to a compound. The compound providing the acyl group is called the acylating agent....

 reactions. This reaction type is a form of electrophilic aromatic substitution

Electrophilic aromatic substitution

Electrophilic aromatic substitution EAS is an organic reaction in which an atom, usually hydrogen, appended to an aromatic system is replaced by an electrophile...

. The general reaction scheme is shown below.

Several reviews have been written.
Friedel–Crafts alkylation involves the alkylation of an aromatic ring with an alkyl halide using a strong Lewis acid

Lewis acid

]The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in 1923, specifically: An acid substance is one which can employ a lone pair from another molecule in completing the stable group of one of its own atoms. Thus, H+ is a Lewis acid, since it can accept a lone pair,...

 catalyst.