Textbook Question
Show how you would add a Grignard reagent to an ester or a nitrile to synthesize
(c) pentan-2-one.
1
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Ch. 21 - Carboxylic Acid Derivatives
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 21, Problem 28b
Show how you would add a Grignard reagent to an ester or a nitrile to synthesize
(b) heptan-4-ol.
Verified step by step guidance1
Identify the target molecule, heptan-4-ol, which is a secondary alcohol with seven carbon atoms. This means the Grignard reagent must add to a precursor molecule to form this structure.
Choose the appropriate precursor molecule. For an ester, the Grignard reagent will add twice to form a tertiary alcohol. For a nitrile, the Grignard reagent will add once to form a ketone, which can then be reduced to a secondary alcohol.
For the ester pathway: Select an ester with a three-carbon chain (e.g., ethyl propanoate). React it with a Grignard reagent containing a four-carbon chain (e.g., butylmagnesium bromide, \( \text{C}_4\text{H}_9\text{MgBr} \)). The first addition forms a ketone intermediate, and the second addition forms the tertiary alcohol.
For the nitrile pathway: Select a nitrile with a three-carbon chain (e.g., propanenitrile). React it with the same Grignard reagent (butylmagnesium bromide). This forms a ketone intermediate (heptan-4-one) after hydrolysis. Reduce the ketone to a secondary alcohol using a reducing agent like \( \text{NaBH}_4 \) or \( \text{LiAlH}_4 \).
Ensure proper reaction conditions: For the Grignard reaction, use an anhydrous ether solvent to prevent deactivation of the Grignard reagent. For the reduction step, use appropriate conditions for the chosen reducing agent. Finally, confirm the structure of heptan-4-ol using spectroscopic techniques like \( ^1\text{H NMR} \) or IR spectroscopy.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Grignard Reagents
Grignard reagents are organomagnesium compounds represented as R-MgX, where R is an organic group and X is a halogen. They are highly reactive nucleophiles that can add to electrophiles, such as carbonyl compounds. In the context of synthesizing alcohols, Grignard reagents can react with esters or nitriles to form alcohols after hydrolysis.
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Ester Reactivity
Esters are organic compounds formed from the reaction of an alcohol and a carboxylic acid. They contain a carbonyl group (C=O) adjacent to an ether group (C-O). When a Grignard reagent is added to an ester, it first forms a tetrahedral intermediate, which then leads to the formation of a tertiary alcohol after hydrolysis, making it a key step in synthesizing heptan-4-ol.
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Nitrile Reactivity
Nitriles are organic compounds containing a cyano group (C≡N) and can be converted into primary amines or alcohols through nucleophilic addition. When a Grignard reagent reacts with a nitrile, it adds to the carbon of the cyano group, forming an intermediate that can be hydrolyzed to yield a primary alcohol. This pathway is also relevant for synthesizing heptan-4-ol.
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Related Practice
Textbook Question
Draw a mechanism for the acidic hydrolysis of the magnesium salt shown below to acetophenone.
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Textbook Question
Draw a mechanism for the reaction of propanoyl chloride with 2 moles of phenylmagnesium bromide.
1
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Textbook Question
Show how Friedel–Crafts acylation might be used to synthesize the following compounds.
a. acetophenone
1
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Textbook Question
Show how Friedel–Crafts acylation might be used to synthesize the following compounds.
b. benzophenone
8
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Textbook Question
Show how you would add a Grignard reagent to an ester or a nitrile to synthesize
(a) 4-phenylheptan-4-ol.
1
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