Textbook Question
Propose mechanisms for the following reactions.
(a)
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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 45a
Synthesize from benzene. (Hint: All of these require diazonium ions.)
(a) 3-ethylbenzoic acid
Verified step by step guidance1
Step 1: Start with benzene as the base compound. Perform a Friedel-Crafts alkylation using ethyl chloride (CH₃CH₂Cl) and aluminum chloride (AlCl₃) as a catalyst to introduce an ethyl group onto the benzene ring, forming ethylbenzene.
Step 2: Nitrate the ethylbenzene by reacting it with a mixture of concentrated nitric acid (HNO₃) and sulfuric acid (H₂SO₄). This introduces a nitro group (-NO₂) onto the benzene ring, forming nitroethylbenzene. The nitro group will preferentially go to the meta position relative to the ethyl group due to the electron-donating nature of the ethyl group.
Step 3: Reduce the nitro group (-NO₂) to an amino group (-NH₂) by using a reducing agent such as tin (Sn) and hydrochloric acid (HCl), forming meta-ethylaminobenzene.
Step 4: Convert the amino group (-NH₂) into a diazonium ion (-N₂⁺) by treating the compound with sodium nitrite (NaNO₂) and hydrochloric acid (HCl) at 0–5°C. This forms meta-ethylbenzenediazonium chloride.
Step 5: Replace the diazonium group (-N₂⁺) with a carboxylic acid group (-COOH) by performing a Sandmeyer reaction using copper(I) cyanide (CuCN), followed by hydrolysis of the resulting nitrile group (-CN) with aqueous acid or base. This yields 3-ethylbenzoic acid.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Benzene and its Derivatives
Benzene is a fundamental aromatic hydrocarbon characterized by its stable ring structure and delocalized π-electrons. Understanding benzene's reactivity is crucial, as it undergoes electrophilic substitution reactions rather than addition, allowing for the introduction of various substituents, such as carboxylic acids or alkyl groups, onto the ring.
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02:49
Aromatic synthesis starting with benzene/benzene derivatives
Diazonium Ions
Diazonium ions are highly reactive intermediates formed from primary aromatic amines and nitrous acid. They play a pivotal role in organic synthesis, particularly in the formation of substituted aromatic compounds through reactions like Sandmeyer or azo coupling, which are essential for synthesizing compounds like 3-ethylbenzoic acid from benzene.
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Electrophilic Substitution Reactions
Electrophilic substitution reactions are a class of reactions where an electrophile replaces a hydrogen atom on an aromatic ring. This mechanism is vital for modifying aromatic compounds, allowing for the introduction of functional groups, such as carboxylic acids, which is necessary for synthesizing 3-ethylbenzoic acid from benzene using diazonium ions.
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01:47Nucleophiles and Electrophiles can react in Substitution Reactions.
Related Practice
Textbook Question
Synthesize from benzene. (Hint: All of these require diazonium ions.)
(d) 4-methoxyaniline
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Textbook Question
The following drugs are synthesized using the methods in this chapter and in previous chapters. Devise a synthesis for each, starting with any compounds containing no more than six carbon atoms.
(b) Methamphetamine, once considered a safe diet pill, but now known to be addictive and destructive to brain tissue.
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Textbook Question
The following drugs are synthesized using the methods in this chapter and in previous chapters. Devise a synthesis for each, starting with any compounds containing no more than six carbon atoms.
(c) Dopamine, one of the neurotransmitters in the brain. Parkinson’s disease is thought to result from a dopamine deficiency.
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Textbook Question
Synthesize Novocaine from benzene and any other reagents of four carbons or fewer.
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Textbook Question
Synthesize from benzene. (Hint: All of these require diazonium ions.)
(c) 2-methyl-5-hydroxybenzoic acid
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