Question

Which of the following can't be used in Friedel- Crafts' reactions?

• A. $FeC{l}_3$
• B. $FeB{r}_2$
• C. $AlC{l}_3$
• D. $NaCl$

Answer 1

Answer: (D)

Friedel-Craft's reaction : This reaction is used for alkylation or acylation of benzene and is initiated by electrophilic attack on benzene. Electrophile is produced in the presence of any Lewis acid viz $AlC{l}_{3}FeC{l}_3,FeB{r}_3$ etc. $NaCl$ is not a Lewis acid hence, cannot be used.

Electrophile is generated as follows
$C{H}_{3}Cl+AlC{l}_3\to AlC{l}_4^{-}+\underset{{\text{ (Carbocation El }}^{-}+\text{) }}{+C{H}_3}$