Textbook Question
Show how you would convert aniline to the following compounds.
(a) fluorobenzene
(b) chlorobenzene
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Ch. 19 - Amines
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 19, Problem 24
Propose a mechanism for the synthesis of methyl orange.
Verified step by step guidance1
Step 1: Begin by identifying the two reactants in the synthesis of methyl orange. The first reactant is dimethylaniline (N(CH3)2 group attached to a benzene ring), and the second reactant is a diazonium salt derived from sulfanilic acid (COOH group and diazonium group attached to a benzene ring). This reaction is an example of an azo coupling reaction.
Step 2: Prepare the diazonium salt. Sulfanilic acid is treated with sodium nitrite (NaNO2) and hydrochloric acid (HCl) under cold conditions to form the diazonium salt. The reaction involves the formation of nitrous acid (HNO2), which reacts with the amine group (-NH2) of sulfanilic acid to produce the diazonium ion (-N≡N⁺).
Step 3: Activate the dimethylaniline for electrophilic substitution. The dimethylaniline acts as the nucleophile in the azo coupling reaction. The electron-donating dimethylamino group (-N(CH3)2) increases the electron density on the benzene ring, making it more reactive toward the electrophilic diazonium ion.
Step 4: Perform the azo coupling reaction. The diazonium ion reacts with the dimethylaniline at the para position relative to the dimethylamino group. This position is favored due to steric and electronic effects. The reaction forms a new azo bond (-N=N-) between the two aromatic rings.
Step 5: Finalize the product. The resulting compound is methyl orange, an azo dye. It contains the dimethylaniline moiety connected to the sulfanilic acid moiety via the azo bond. The structure includes the -N=N- linkage, the dimethylamino group, and the sulfonic acid group (-SO3H) from sulfanilic acid.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Diazo Compounds
Diazo compounds are organic compounds containing two nitrogen atoms connected by a double bond (N=N). They are typically generated from primary amines and are highly reactive, often used in coupling reactions to form azo compounds. In the synthesis of methyl orange, diazo compounds play a crucial role in the formation of the azo linkage that characterizes the dye.
Azo Coupling Reaction
Azo coupling is a reaction between a diazonium salt and an activated aromatic compound, leading to the formation of azo compounds, which contain the -N=N- functional group. This reaction is essential in dye chemistry, as it allows for the creation of vibrant colors. In the case of methyl orange, the coupling of a diazonium salt with an aromatic amine is a key step in its synthesis.
Electrophilic Aromatic Substitution
Electrophilic aromatic substitution (EAS) is a fundamental reaction in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. This mechanism is vital for introducing functional groups into aromatic compounds. In the synthesis of methyl orange, EAS is involved when the diazonium salt acts as the electrophile, reacting with the aromatic amine to form the final product.
Related Practice
Textbook Question
Predict the products from the reactions of the following amines with sodium nitrite in dilute HCl.
(b) N-ethylhexan-2-amine
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Textbook Question
Give the expected products of lithium aluminum hydride reduction of the following compounds (followed by hydrolysis).
(a) butyronitrile
(b) N-cyclohexylacetamide
(c) ε-caprolactam
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Textbook Question
Predict the products from the reactions of the following amines with sodium nitrite in dilute HCl.
(d) aniline
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Textbook Question
Predict the products from the reactions of the following amines with sodium nitrite in dilute HCl.
(c) piperidine
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Textbook Question
Show how you would convert aniline to the following compounds.
(c) 1,3,5-trimethylbenzene
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