Question:
Which of the following yields Tarry product during oxidation:
Which of the following yields Tarry product during oxidation:
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To successfully nitrate aniline without generating tarry products, the amino group must first be "protected" by acetylation (reacting with acetic anhydride to form acetanilide). After nitration of the ring, the acetyl group is removed via hydrolysis.
Updated On: Apr 21, 2026
- oxidation of aniline by nitric acid (Nitration of aniline)
- Sulphonation of aniline
- Bromination of aniline
- Friedal carft alkylation of aniline
- Friedal craft acylation of aniline
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The Correct Option is A
Solution and Explanation
Step 1: Understanding the Concept:
Aniline (\(\text{C}_6\text{H}_5\text{NH}_2\)) is an aromatic amine where the \(\text{-NH}_2\) group strongly activates the benzene ring towards electrophilic substitution. However, this same \(\text{-NH}_2\) group makes the molecule highly susceptible to oxidation by strong oxidizing agents.
Step 2: Key Formula or Approach:
The approach requires evaluating the reagents used in each reaction option and determining if they act as strong oxidizing agents capable of destructively oxidizing the delicate amino group on the aromatic ring.
Step 3: Detailed Explanation:
Let's analyze the given reactions:
- A) Nitration of aniline: The standard reagent for nitration is a mixture of concentrated nitric acid (\(\text{HNO}_3\)) and concentrated sulfuric acid. Nitric acid is not only a nitrating agent but also a very powerful oxidizing agent. When aniline is treated directly with this mixture, the highly sensitive amino group is severely oxidized, leading to the formation of a complex mixture of dark, intractable, "tarry" oxidation products, severely reducing the yield of the desired nitroanilines.
- B) Sulphonation of aniline: This involves heating aniline with concentrated sulfuric acid. It forms an intermediate anilinium hydrogen sulfate, which rearranges to form sulfanilic acid. It does not produce tarry oxidation products.
- C) Bromination of aniline: Aniline reacts rapidly with bromine water to form a white precipitate of 2,4,6-tribromoaniline. While the ring is highly activated, bromine water does not cause the massive tarry oxidation seen with nitric acid.
- D) & E) Friedel-Crafts reactions: Aniline does not undergo Friedel-Crafts alkylation or acylation. The lone pair on the nitrogen atom strongly coordinates with the Lewis acid catalyst (e.g., \(\text{AlCl}_3\)), forming an insoluble salt complex. This deactivates the ring and stops the reaction. It yields no product, let alone a tarry one.
Step 4: Final Answer:
Direct nitration with nitric acid causes severe oxidation resulting in tarry products.
Aniline (\(\text{C}_6\text{H}_5\text{NH}_2\)) is an aromatic amine where the \(\text{-NH}_2\) group strongly activates the benzene ring towards electrophilic substitution. However, this same \(\text{-NH}_2\) group makes the molecule highly susceptible to oxidation by strong oxidizing agents.
Step 2: Key Formula or Approach:
The approach requires evaluating the reagents used in each reaction option and determining if they act as strong oxidizing agents capable of destructively oxidizing the delicate amino group on the aromatic ring.
Step 3: Detailed Explanation:
Let's analyze the given reactions:
- A) Nitration of aniline: The standard reagent for nitration is a mixture of concentrated nitric acid (\(\text{HNO}_3\)) and concentrated sulfuric acid. Nitric acid is not only a nitrating agent but also a very powerful oxidizing agent. When aniline is treated directly with this mixture, the highly sensitive amino group is severely oxidized, leading to the formation of a complex mixture of dark, intractable, "tarry" oxidation products, severely reducing the yield of the desired nitroanilines.
- B) Sulphonation of aniline: This involves heating aniline with concentrated sulfuric acid. It forms an intermediate anilinium hydrogen sulfate, which rearranges to form sulfanilic acid. It does not produce tarry oxidation products.
- C) Bromination of aniline: Aniline reacts rapidly with bromine water to form a white precipitate of 2,4,6-tribromoaniline. While the ring is highly activated, bromine water does not cause the massive tarry oxidation seen with nitric acid.
- D) & E) Friedel-Crafts reactions: Aniline does not undergo Friedel-Crafts alkylation or acylation. The lone pair on the nitrogen atom strongly coordinates with the Lewis acid catalyst (e.g., \(\text{AlCl}_3\)), forming an insoluble salt complex. This deactivates the ring and stops the reaction. It yields no product, let alone a tarry one.
Step 4: Final Answer:
Direct nitration with nitric acid causes severe oxidation resulting in tarry products.
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