Question

In a Friedel-Crafts Alkylation, there are multiple continuous reactions. But in the Friedel-Crafts Acylation, the reaction stops after producing the first product. Explain why.

CH3 CH3 CH3C1 AICI: + Нас (Product mixture) CCH3 CH3CCI AlCl3 (Sole product)

Answer 1

In friedel crafts alkylation there is a chance of polyalkyation . Because the alkyl group increases benzene ring electron density and ring becomes activated to another elelctrophilic substitution. Thus continuous reactions takes palce. But in Fridel crafts acylation there is no chance of polyacylation because the acyl group (RC=0) decreases benzene ring electron density and hence the second acylation does not take place and it gives only one product.