Friedel-Craft reaction
| Friedel-Crafts reaction | |
|---|---|
| Named after |
Charles Friedel James Crafts |
| Reaction type | Coupling reaction |
| Identifiers | |
| RSC ontology ID | RXNO:0000369 |
| Friedel-Crafts alkylation | |
|---|---|
| Named after |
Charles Friedel James Crafts |
| Reaction type | Coupling reaction |
| Identifiers | |
| Organic Chemistry Portal | friedel-crafts-alkylation |
| RSC ontology ID | RXNO:0000046 |
| Friedel-Crafts acylation | |
|---|---|
| Named after |
Charles Friedel James Crafts |
| Reaction type | Coupling reaction |
| Identifiers | |
| Organic Chemistry Portal | friedel-crafts-acylation |
| RSC ontology ID | RXNO:0000045 |
The Friedel–Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877 to attach substituents to an aromatic ring. Friedel–Crafts reactions are of two main types: alkylation reactions and acylation reactions. Both proceed by electrophilic aromatic substitution.
Friedel–Crafts alkylation involves the alkylation of an aromatic ring with an alkyl halide using a strong Lewis acid catalyst. With anhydrous ferric chloride as a catalyst, the alkyl group attaches at the former site of the chloride ion. The general mechanism is shown below.
This reaction suffers from the disadvantage that the product is more nucleophilic than the reactant. Consequenly, overalkylation occurs. Furthermore, the reaction is only very useful for tertiary carbon and secondary alkylating agents. Otherwise the incipient carbocation (R+) will undergo a carbocation rearrangement reaction.
Steric hindrance can be exploited to limit the number of alkylations, as in the t-butylation of 1,4-dimethoxybenzene.
Alkylations are not limited to alkyl halides: Friedel–Crafts reactions are possible with any carbocationic intermediate such as those derived from alkenes and a protic acid, Lewis acid, enones, and epoxides. An example is the synthesis of neophyl chloride from benzene and methallyl chloride:
...
Wikipedia