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Muneer Ahmed

What is the purpose of adding hydrochloric acid in the reaction mixture?

Carlos Torres  Follow

I am basing this on the procedure from the University of Michigan: http://www.umich.edu/~chem216/216%20S11-Expt%201.pdf

The purpose of adding HCl is to convert aniline to its hydrochloride salt. This makes aniline soluble in water.

Typically, this reaction can be done without HCl. While aniline does not dissolve in water, it reacts quite well with acetic anhydride when the two are mixed in water.

I haven’t done the reaction with HCl, but it may well increase the yield somewhat by improving contact between the reactants.

Edit to address the further question in the comments:

Sodium acetate is a base. Its purpose is to generate small amounts of free aniline by deprotonating the hydrochloride salt. This free aniline is what reacts with acetic anhydride

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Barbara Carlson  Follow

What reaction mixture are you talking about? What reaction? Can you be more specific? There can be dozens of reasons why you want to add HCl to a certain reaction:

  1. you may want to reach a specific pH value;
  2. the H+ ions released me be catalysing the reaction;
  3. you need to protonate a given species for the reaction to get going.

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