Acylation of aromatic rings

An acyl group, -COR (pronounced a-sil), is introduced onto the ring when an aromatic compound reacts with a carboxylic acid chloride, RCOCl, in the presence of AICI3. For example, reaction of benzene with acetyl chloride yields the ketone, acetophenone. 

Mechanism of the Friedel-Crafts acylation reaction. The electrophile is a resonance-itabilized acyl cation, whose electrostatic potential map indicates carbon as the most positive atom (blue). 

Unlike the multiple substitutions that often occur in Friedel-Crafts alkylations, acylations never occur more than once on a ring because the product acylbenzene is always less reactive than the nonacylated starting material. We ll account for these reactivity differences in the next section. 

Problem 16.6 Identify the carboxylic acid chloride that might be used in a Friedel-Crafts acylation reaction to prepare each of the foilomng acylbenaenes  

Onlj one product can form when an electrophilic substitution occurs on benzene, but what would happen if we were to carry out a reaction on an aromatic ring that already has a substituent A substituent already present on the ring has two effects  

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One of the most useful reac tions of acyl chlorides was presented in Section 12 7 Friedel-Crafts acylation of aromatic rings takes place when arenes are treated with acyl chlorides in the presence of aluminum chloride... 

Alkylation and Acylation of Aromatic Rings The Friedel-Crafts Reaction 555... 

Acylation of aromatic rings with nitriles (Hoesch)... 

The useful disconnection 6a corresponds to Friedel-Crafts acylation of aromatic rings and is the obvious one on the ketone 6 having the perfume of hawthorn blossom. Reaction2 of ether 7 with MeCOCl and AICI3 gives 6 in 94-96% yield—a good reaction indeed. 

Friedel-Crafts Acylation of Aromatic Rings In the presence of aluminum chloride, acyl halides acylate benzene, halobenzenes, and activated benzene derivatives. Friedel-Crafts acylation is discussed in detail in Section 17-11. 

Bromination of Aromatic Rings 593 Other Aromatic Substitutions 597 Alkylation of Aromatic Rings The Friedel-Crafts Reaction Acylation of Aromatic Rings 604 Substituent Effects in Substituted Aromatic Rings 605 An Explanation of Substituent Effects 610 Trisubstituted Benzenes Additivity of Effects... 

Acyl halides are used to synthesize aromatic ketones, through Friedel-Crafts acylation of aromatic rings (review Sec. 4.9.d). 

Discovered in 1877, the Friedel-Crafts reaction is one of the more important and useful organic transformations. This class of reactions is generally considered to include all Lewis acid-promoted electrophilic alkylations and acylations of aromatic rings. Due to their synthetic utility, Friedel-Crafts reactions have been extensively studied and used across a broad and diverse area of chemical research. 

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