Textbook Question
Show how you would use Grignard syntheses to prepare the following alcohol from the indicated starting material and any other necessary reagents.
(a) octan-3-ol from hexanal, CH3(CH2)4CHO
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Ch.10 - Structure and Synthesis of Alcohols
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 10, Problem 39g
Show how you would use Grignard syntheses to prepare the following alcohol from the indicated starting material and any other necessary reagents.
(g) cyclopentylphenylmethanol from benzaldehyde (Ph–CHO)
Verified step by step guidance1
Identify the target alcohol and the starting material: The target alcohol is cyclopentylphenylmethanol, and the starting material is benzaldehyde (Ph-CHO). The Grignard reagent will be used to introduce the cyclopentyl group to the benzaldehyde.
Prepare the Grignard reagent: React cyclopentyl bromide (C5H9Br) with magnesium (Mg) in anhydrous ether to form cyclopentylmagnesium bromide (C5H9MgBr). This is the nucleophilic reagent that will attack the carbonyl group of benzaldehyde.
Perform the Grignard reaction: Add the Grignard reagent (C5H9MgBr) to benzaldehyde (Ph-CHO) in an anhydrous ether solvent. The nucleophilic carbon in the Grignard reagent will attack the electrophilic carbon of the carbonyl group, forming a tetrahedral alkoxide intermediate.
Protonate the alkoxide intermediate: After the Grignard reaction, perform an acidic workup by adding a dilute acid (e.g., HCl or H2SO4) to protonate the alkoxide intermediate. This step converts the alkoxide into the desired alcohol, cyclopentylphenylmethanol.
Verify the product: Confirm the structure of the product using spectroscopic techniques such as NMR or IR to ensure that cyclopentylphenylmethanol has been successfully synthesized.
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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, typically represented as R-MgX, where R is an organic group and X is a halogen. They are highly reactive and can act as nucleophiles, attacking electrophilic carbon centers in carbonyl compounds. In the context of synthesizing alcohols, Grignard reagents can react with aldehydes or ketones to form alcohols after subsequent hydrolysis.
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Carbonation of Grignard Reagents
Nucleophilic Addition
Nucleophilic addition is a fundamental reaction mechanism in organic chemistry where a nucleophile attacks an electrophilic carbon atom, leading to the formation of a new bond. In the case of Grignard synthesis, the nucleophile (Grignard reagent) adds to the carbonyl carbon of benzaldehyde, resulting in the formation of an alkoxide intermediate, which can be protonated to yield the desired alcohol.
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Alcohol Formation
The formation of alcohols from carbonyl compounds involves the reduction of the carbonyl group. In the Grignard synthesis, after the nucleophilic addition of the Grignard reagent to the carbonyl carbon, the resulting alkoxide can be converted to an alcohol by adding water or an acid. This process is crucial for transforming the initial reactants into the target alcohol, cyclopentylphenylmethanol in this case.
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Related Practice
Textbook Question
Show how you would accomplish the following transformations. You may use any additional reagents you need.
(c)
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Textbook Question
Show how you would use Grignard syntheses to prepare the following alcohol from the indicated starting material and any other necessary reagents.
(e) benzyl alcohol (Ph–CH2–OH) from bromobenzene (Ph–Br)
672
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Textbook Question
Show how you would accomplish the following transformations. You may use any additional reagents you need.
(d)
1592
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Textbook Question
Show how you would use Grignard syntheses to prepare the following alcohol from the indicated starting material and any other necessary reagents.
(d) 2-cyclohexylethanol from bromocyclohexane
616
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Textbook Question
Show how you would accomplish the following transformations. You may use any additional reagents you need.
(b)
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