A. An unknown liquid boiling around 185 +/- 5 degrees C in 5% HCl but is insolub

Question

A. An unknown liquid boiling around 185 +/- 5 degrees C in 5% HCl but is insoluble in water and in a pH 5.5 buffer. Shaking the unknown with p-touluenesulfonyl chloride in aqueous NaOH produces a clear solution that, when acidified, yields a white precipitate. Give its name and structure.

B. An unknown liquid boiling around 185 +/- 5 degrees C in 5% HCl and in a pH 5.5 buffer but is insoluble in water. Shaking the unknown with p-touluenesulfonyl chloride in aqueous NaOH produces a white precipitate that doesn't dissolve in dilute HCl. Give its name and structure.

Explanation / Answer

A.) The unknown is aniline. Aniline is a primary amine, with a BP of 184, within the tolerance given. Under the Hinsberg test conditions (as stated in the question) with aniline, the product would be soluble in NaOH, and once acidified would precipitate. B.) The unknown is N-ethylbenzamide. This is a secondary amine, with a BP of 183, within the tolerance given. The Hinsberg test with a 2nd amine yields an immediately insoluble precipitate before acidification.

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