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Synthesis of Sulfanilamide: Acetylation of Aniline

1) Why is an acetyl group added to aniline (making acetanilide) and then removed to regenerate the amine group in sulfanilamide?
2) "Dissolve 5.0 g (0.054 mol) of aniline in 135 mL of water and 4.5 mL (0.054 mol) of concentrated of hydrochloric acid; if the solution is colored, filter it by suction through a pad of decolorizing charcoal. Measure out 6.2 mL (0.065 mol) of acetic anhydride; also prepare a solution of 5.3 g (0.065 mol) of anhydrous sodium acetate in 30 mL of water. Add the acetic anhydride to the solution of aniline hydrochloride with stirring and immediately add all of the sodium acetate solution. Stir, cool in ice, and collect the product. It should be colorless, with a melting point close to 1140C. Because the acetaniline must be completely dry for use in the next step, it is advisable to put the material in a tared 125-mL Erlenmeyer flask and to heat this on a steam or sand bath under evacuation until the weight is constant."
Why is aqueous HCl combined with aniline in the above procedure? Explain your answer. Calculate the theoretical yield using the Limiting Reactant.
3) Suppose you plan to make up the specified aqueous solution of sodium acetate after you combine acetic anhydride with the aqueous solution of aniline. Why is this not an appropriate strategy? Explain your answer.
4) Show step by step the mechanism for acetylation of aniline with acetic anhydride.
5) How are unreacted aniline and acetic anhydride separated from the acetanilide product in the procedure for #2?
6) Why is aniline soluble in aqueous hydrochloric acid whereas acetanilide is not? Explain your answer through illustration if necessary.

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Solution Summary

The acetylation reaction in the synthesis of sulfanilamide is discussed. Questions are answered in detail.

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