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

19. Reactions of Aromatics: EAS and Beyond

Diazo Retrosynthesis

Organic Chemistry

19. Reactions of Aromatics: EAS and Beyond

Diazo Retrosynthesis

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Problem 34

Textbook Question

Draw the structure of the activated benzene ring and the diazonium ion used in the synthesis of each of the following compounds, whose structures can be found on page 607.
b. methyl orange

Verified step by step guidance

Identify the structure of methyl orange, which is an azo dye. It contains an azo group (-N=N-) linking two aromatic rings, one of which is substituted with a sulfonic acid group (-SO3H) and the other with a methyl group (-CH3).

Understand that the synthesis of methyl orange involves a diazonium coupling reaction. This reaction requires a diazonium ion and an activated benzene ring. The diazonium ion is typically derived from an aromatic amine through diazotization.

Determine the structure of the diazonium ion. In this case, the diazonium ion is derived from sulfanilic acid (an aromatic amine with a -SO3H group). The diazonium ion is formed by treating sulfanilic acid with sodium nitrite (NaNO2) and hydrochloric acid (HCl) under cold conditions, resulting in the structure: \( \text{C}_6\text{H}_4\text{SO}_3^-\text{N}_2^+ \).

Identify the activated benzene ring. The coupling partner in this reaction is N,N-dimethylaniline, which has a benzene ring activated by the electron-donating dimethylamino group (-N(CH3)2). This group increases the electron density on the benzene ring, making it more reactive toward electrophilic attack by the diazonium ion.

Combine the diazonium ion and the activated benzene ring. The diazonium ion acts as an electrophile and reacts with the activated benzene ring of N,N-dimethylaniline at the para position relative to the -N(CH3)2 group. This forms the azo bond (-N=N-) and results in the structure of methyl orange.

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Key Concepts

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

Activated Benzene Ring

An activated benzene ring is a benzene derivative that has substituents that increase its reactivity towards electrophilic aromatic substitution. These substituents, such as -OH or -NH2, donate electron density to the ring, making it more nucleophilic. Understanding the structure and reactivity of activated benzene is crucial for predicting the outcomes of reactions involving electrophiles.

Diazonium Ion

A diazonium ion is a positively charged species with the general formula R-N2^+, where R is an aryl group. It is formed by the reaction of an aromatic amine with nitrous acid and is a key intermediate in various organic reactions, particularly in the synthesis of azo compounds. The diazonium ion can undergo substitution reactions to introduce new functional groups onto the aromatic ring.

Methyl Orange Structure

Methyl orange is a pH indicator that changes color based on the acidity of the solution. Its structure includes a diazo compound linked to a sulfonic acid group, which contributes to its solubility and color change properties. Understanding the molecular structure of methyl orange is essential for recognizing how it interacts with acids and bases, as well as its synthesis from diazonium ions.

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