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 21a1
Show how the following ketones might be synthesized from the indicated acids, using any necessary reagents.
(a) propiophenone from propionic acid (using alkylation of the acid)
Verified step by step guidance1
Start with the given acid, propionic acid (CH₃CH₂COOH). The goal is to convert this carboxylic acid into a ketone, propiophenone (C₆H₅COCH₂CH₃).
First, convert the carboxylic acid into an acid chloride. This can be achieved by reacting propionic acid with thionyl chloride (SOCl₂) or oxalyl chloride. The reaction produces propionyl chloride (CH₃CH₂COCl) and releases HCl and SO₂ as byproducts.
Next, perform a Friedel-Crafts acylation reaction. React the propionyl chloride with benzene (C₆H₆) in the presence of a Lewis acid catalyst, such as aluminum chloride (AlCl₃). This step introduces the acyl group (CH₃CH₂CO-) onto the benzene ring, forming propiophenone.
After the reaction, perform a workup to neutralize the reaction mixture and isolate the product. This typically involves quenching the reaction with water or dilute acid to remove the catalyst and any remaining reagents.
Finally, purify the product, propiophenone, using techniques such as distillation or recrystallization to ensure it is free of impurities.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Alkylation of Carboxylic Acids
Alkylation of carboxylic acids involves the introduction of an alkyl group to the acid, typically through a reaction with an alkyl halide in the presence of a base. This process allows for the formation of a new carbon-carbon bond, which is essential for synthesizing ketones from acids. In the case of propionic acid, the alkylation can lead to the formation of a propanoyl group, which is a precursor to propiophenone.
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Carboxylic Acids Nomenclature
Reagents for Alkylation
Common reagents used in the alkylation of carboxylic acids include alkyl halides and strong bases such as sodium hydride or lithium diisopropylamide (LDA). The base deprotonates the carboxylic acid, generating a carbanion that can then attack the alkyl halide, resulting in the formation of a new carbon chain. Choosing the right alkyl halide is crucial for achieving the desired ketone structure.
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Formation of Ketones
Ketones are organic compounds characterized by a carbonyl group (C=O) flanked by two carbon atoms. In the synthesis of propiophenone from propionic acid, the alkylation process introduces an additional carbon chain, leading to the formation of the ketone. Understanding the structure and reactivity of ketones is vital for predicting their behavior in further reactions and their applications in organic synthesis.
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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 synthesize the following compounds from the appropriate carboxylic acids or acid derivatives.
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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
Draw the following sugars using Haworth projections:
b. α-D-tagatopyranose
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