Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

26. Amines

Amines by Reduction

Organic Chemistry

26. Amines

Amines by Reduction

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3:40 minutes

Problem 31a

Textbook Question

Show how to prepare the following aromatic amines by aromatic nitration, followed by reduction. You may use benzene and toluene as your aromatic starting materials.
(a) aniline

Verified step by step guidance

Step 1: Begin with benzene as the aromatic starting material. Benzene is a simple aromatic compound with a six-membered ring and alternating double bonds.

Step 2: Perform aromatic nitration on benzene. This involves reacting benzene with a mixture of concentrated nitric acid (HNO₃) and concentrated sulfuric acid (H₂SO₄). The reaction introduces a nitro group (-NO₂) onto the benzene ring, forming nitrobenzene. The general reaction is: C₆H₆ + HNO₃ → C₆H₅NO₂ + H₂O.

Step 3: Reduce the nitro group (-NO₂) in nitrobenzene to an amino group (-NH₂). This reduction can be achieved using reagents such as tin (Sn) and hydrochloric acid (HCl), or catalytic hydrogenation (H₂ with a metal catalyst like Pd/C). The reaction converts nitrobenzene to aniline (C₆H₅NH₂).

Step 4: If toluene is used as the starting material instead of benzene, the nitration reaction will preferentially occur at the ortho and para positions relative to the methyl group (-CH₃) due to its electron-donating nature. This results in a mixture of ortho-nitrotoluene and para-nitrotoluene.

Step 5: Reduce the nitro group in para-nitrotoluene to form para-toluidine (C₆H₄CH₃NH₂). This compound is structurally similar to aniline but contains a methyl group on the ring. If pure aniline is required, benzene should be used as the starting material.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Aromatic Nitration

Aromatic nitration is a chemical reaction that introduces a nitro group (-NO2) into an aromatic ring, typically using a mixture of concentrated nitric acid and sulfuric acid. This electrophilic substitution reaction is facilitated by the formation of a nitronium ion (NO2+), which acts as the electrophile. The position of substitution is influenced by the existing substituents on the aromatic ring, which can either activate or deactivate the ring towards further electrophilic attacks.

Reduction of Nitro Compounds

The reduction of nitro compounds involves converting the nitro group (-NO2) into an amine group (-NH2). This transformation can be achieved through various methods, including catalytic hydrogenation or using reducing agents like iron and hydrochloric acid. The reduction process is crucial for synthesizing aromatic amines, as it allows for the functionalization of the aromatic ring, leading to compounds like aniline, which is a key building block in organic synthesis.

Electrophilic Aromatic Substitution (EAS)

Electrophilic Aromatic Substitution (EAS) is a fundamental reaction mechanism in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. This process is characterized by the formation of a sigma complex (arenium ion) and is influenced by the nature of substituents already present on the ring. Understanding EAS is essential for predicting the outcomes of reactions involving aromatic compounds, such as the nitration and subsequent reduction to form aromatic amines.

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