Textbook Question
Show how the following ketones might be synthesized from the indicated acids, using any necessary reagents.
(b) methyl cyclohexyl ketone from cyclohexanecarboxylic acid
Ch. 20 - Carboxylic Acids
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 20, Problem 23b
Propose mechanisms for the nucleophilic acyl substitutions to form N-methylacetamide as shown on the previous page.
Verified step by step guidance1
Step 1: Identify the starting material and the product. The starting material is benzoyl chloride (PhCOCl), and the product is N-methylacetamide (PhCONHCH3). This reaction involves nucleophilic acyl substitution, where the chlorine atom is replaced by the N-methylamide group.
Step 2: Recognize the nucleophile and base. Methylamine (CH3NH2) acts as the nucleophile, and sodium hydroxide (NaOH) serves as the base to neutralize the HCl byproduct formed during the reaction.
Step 3: Initiate the mechanism with the nucleophilic attack. The lone pair of electrons on the nitrogen atom of CH3NH2 attacks the carbonyl carbon of benzoyl chloride, forming a tetrahedral intermediate. This step is driven by the electrophilic nature of the carbonyl carbon due to the electron-withdrawing chlorine atom.
Step 4: Collapse of the tetrahedral intermediate. The tetrahedral intermediate collapses, expelling the chloride ion (Cl⁻) as a leaving group and forming the amide bond (C-N). This step restores the carbonyl group in the product.
Step 5: Neutralization of the byproduct. The expelled HCl reacts with NaOH to form NaCl and water, ensuring the reaction proceeds efficiently without acid buildup. The final product, N-methylacetamide, is formed.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Nucleophilic Acyl Substitution
Nucleophilic acyl substitution is a fundamental reaction in organic chemistry where a nucleophile attacks the carbonyl carbon of an acyl compound, leading to the replacement of a leaving group (such as a halide) with the nucleophile. This mechanism is crucial for forming amides, esters, and other derivatives from carboxylic acids and their derivatives.
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Mechanism Steps
The mechanism of nucleophilic acyl substitution typically involves several key steps: nucleophilic attack on the carbonyl carbon, formation of a tetrahedral intermediate, and subsequent elimination of the leaving group. Understanding these steps is essential for predicting the outcome of the reaction and the stability of intermediates formed during the process.
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Role of Base Catalysis
In the provided reaction, sodium hydroxide (NaOH) acts as a base that can deprotonate the nucleophile (methylamine, CH3NH2), enhancing its nucleophilicity. Base catalysis is often employed in nucleophilic acyl substitutions to facilitate the reaction by increasing the reactivity of the nucleophile and stabilizing the transition state.
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Related Practice
Textbook Question
Propose mechanisms for the nucleophilic acyl substitutions to form ethyl benzoate as shown on the previous page.
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Textbook Question
Show how you would use an acid chloride as an intermediate to synthesize
(b) phenyl propionate (CH3CH2COOPh) from propionic acid and phenol.
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Textbook Question
Give the IUPAC names of the following compounds.
(a) CH3CH2C≡CCOOH
(b) CH3CH(NH2)CH(OH)COOH
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Textbook Question
Propose a mechanism for the reaction of benzoic acid with oxalyl chloride. This mechanism begins like the thionyl chloride reaction, to give a reactive mixed anhydride. Nucleophilic acyl substitution by chloride ion gives a tetrahedral intermediate that eliminates a leaving group, which then fragments into carbon dioxide, carbon monoxide, and chloride ion.
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Textbook Question
Show how you would use an acid chloride as an intermediate to synthesize.
(a) N-phenylbenzamide (PhCONHPh) from benzoic acid and aniline.
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