# Friedel-Crafts synthesis - How is HCl produced?

In the mechanism for the acetylation of bromobenzene, how is $\ce{HCl}$ gas produced?

The reactants are acetic anhydride, bromobenzene, $\ce{AlCl3}$ and dichloromethane.

Initially, 4-bromoacetophenone is made, accompanied -by as far as I know - with acetic acid and the regeneration of $\ce{AlCl3}$.

How then is $\ce{HCl}$ produced?

To remove the $\ce{AlCl3}$ at the end, 3 $\ce{H2O}$ are added and $\ce{HCl}$ gas is produced then.

I'm trying to think of ways that $\ce{HCl}$ gas is produced prior to that, however. Could a chlorine of the aluminate ion deprotonate the arenium ion?

Could dichloromethane (solvent) donate a $\ce{Cl-}$ to $\ce{AlCl3}$?

• I suspect your suggestion is correct. $\ce{[AlCl3(OOCCH3)]-}$ loses a chlorine instead of the acetate when deprotonating arenium ion to form $\ce{HCl}$ as a byproduct – bon Feb 2 '15 at 18:40

• I have a question..Are you sure $AlCl_3$ doesn't attack on the middle oxygen? – user35508 Dec 6 '18 at 11:17