Preparation of ethyl benzene from acylation of benzene yields acetophenone which on reduction gives ethyl benzene. The complete reactions can be shown as:
The direct alkylation cannot be performed because polysubstitution product is formed. Due to disadvantage of polysubstitution, the Friedel-Crafts alkylation reaction is not used for the preparation of alkyl benzene. Instead of that, Friedel-Crafts acylation is used.