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The lab sheet says the following :

Reaction of 2,6-dimethylaniline with α-chloroacetyl chloride to α-chloro-2,6-dimethylacetanilide

This reaction is carried out in glacial (anhydrous) acetic acid as the solvent. The acetic acid reacts with 2, 6-dimethylaniline to establish an equilibrium between it and its acetate salt.

What is the purpose of establishing an equilibrium between 2,6-dimethylaniline and its salt here?

EDIT: This is the source of the quoted text & the procedure to synthesize lidocaine : https://tigerweb.towson.edu/jdiscord/www/332_lab_info/summer2016chem332labs/webexpt_lidocaine_a.pdf

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    $\begingroup$ Please don’t point us to a document but quote and include the contents here. $\endgroup$ – Jan Oct 3 '16 at 21:36
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I think acetic acid is used because it allows you to play funny games with the varying solubility of reactants, products, and by-products. Note that the final product is not soluble in acetic acid/water mixture, but the reactants and salt by-products are. This means that instead of performing an extract in a separatory funnel (extra step, plus you'll need to evaporate solvent and purify), you can just filter the solid product directly from the rest of liquid.

This is the kind of simplifying "magic" you can get when the process chemists get a stab at designing how to run the reaction.

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