A2-Level Benzene, Aromatic Chemistry

  • Acylation of benzene involves the substitution of an acyl group onto a benzene ring:


  • Acyl chlorides are reacted with a halogen carrier (AlCl ) to form an acyl ion, which acts as a strong electrophile and reacts with the benzene ring in an electrophilic substitution reaction. 

  • The reaction requires warm conditions, and HCl is formed as a product.



Acylation of Arenes


Acylation of benzene refers to the substitution of an acyl group (RCO⁻) onto a benzene ring. In order to be substituted onto the ring, the acyl group must be an electrophile, and the carbon atom in the acyl group must have a positive charge.




Acyl chlorides are an easy way to form an acyl group with a positive charge on the carbon atom. As with the alkylation of arenes, a halogen carrier is used to break the bond between the carbon atom and the chlorine atom in an acyl chloride.







The electrophile formed can then react with benzene in a standard electrophilic substitution reaction.




HCl is formed at the end of the reaction. The tetra ion formed from the halogen carrier reacts with the hydrogen ion released during the reaction, forming HCl and the original halogen carrier again.