# How do you alkylate benzene?

You can do it via a Friedel-Crafts Alkylation, where you have an alkyl halide and a strong Lewis acid catalyst. Commonly we use ${\text{FeX}}_{3}$ where $\text{X}$ is often $\text{Cl}$ or $\text{Br}$.
The mechanism is as follows, and is very similar to Friedel-Crafts Acylation (and even draws parallels with the benzene halogenation reaction where you have ${\text{X}}_{2}$ in ${\text{FeX}}_{3}$...):