MediumChemistryHigh School (11–12)Organic Compounds with Functional Groups › AminesNumerical

Aniline, 18.6 g, is converted to p-nitroaniline in three steps: acetylation, nitration and…

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Aniline, $18.6\ \text{g}$ , is converted to p-nitroaniline in three steps: acetylation, nitration and hydrolysis. Use $M = 93$ for aniline, $135$ for acetanilide, $180$ for p-nitroacetanilide and $138\ \text{g/mol}$ for p-nitroaniline. The yields are $95\ \%$ for acetylation, $70\ \%$ for the nitration that gives the para product, and $90\ \%$ for hydrolysis. Find the mass of acetanilide after step 1, the mass of p-nitroacetanilide after step 2, the mass of p-nitroaniline after step 3 and the overall yield of the three steps.

Need a reminder? The key ideaShow

The amino group activates the ring and directs to the ortho and para positions. Bromine water gives 2,4,6-tribromoaniline. In strong acid, aniline becomes the anilinium ion, which directs meta. An acetyl group protects the amine: acetylate, react, hydrolyse. The yields of the steps multiply. The ratio of the ion to the free amine is $\dfrac{[\text{BH}^+]}{[\text{B}]} = 10^{\text{p}K_a - \text{pH}}$ .

The worked solution

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