Textbook Question
Show how you would add Grignard reagent to acid chloride or ester to synthesize the following alcohols.
a. Ph3C–OH
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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 17c
Show how you would add Grignard reagent to acid chloride or ester to synthesize the following alcohols.
c. dicyclohexylphenylmethanol
Verified step by step guidance1
Step 1: Understand the reaction mechanism. Grignard reagents (R-MgX) are highly nucleophilic and react with acid chlorides or esters to form alcohols. In this case, the target alcohol is dicyclohexylphenylmethanol, which requires two equivalents of the Grignard reagent to add to the carbonyl group.
Step 2: Identify the starting material. To synthesize dicyclohexylphenylmethanol, you need an acid chloride or ester with a phenyl group attached to the carbonyl carbon. For example, phenylacetyl chloride or phenyl acetate can be used as the starting material.
Step 3: Select the Grignard reagent. The Grignard reagent should contain the cyclohexyl group (C₆H₁₁). For this synthesis, cyclohexylmagnesium bromide (C₆H₁₁-MgBr) is an appropriate choice.
Step 4: Perform the reaction. Add two equivalents of cyclohexylmagnesium bromide to the acid chloride or ester under anhydrous conditions. The first equivalent reacts with the carbonyl group to form a ketone intermediate, and the second equivalent reacts with the ketone to produce the tertiary alcohol.
Step 5: Workup and purification. After the reaction is complete, perform an acidic workup (e.g., using dilute HCl) to protonate the alkoxide intermediate and isolate the alcohol. Purify the product using techniques such as recrystallization or chromatography to obtain dicyclohexylphenylmethanol.
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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 that are highly reactive and used in organic synthesis. They are formed by reacting alkyl or aryl halides with magnesium metal in dry ether. Grignard reagents act as nucleophiles, attacking electrophilic centers such as carbonyl groups in aldehydes, ketones, esters, and acid chlorides, leading to the formation of alcohols after hydrolysis.
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Carbonation of Grignard Reagents
Acid Chlorides and Esters
Acid chlorides and esters are important functional groups in organic chemistry. Acid chlorides are derived from carboxylic acids by replacing the hydroxyl group with a chlorine atom, making them highly reactive. Esters, on the other hand, are formed from the reaction of carboxylic acids with alcohols. Both can react with Grignard reagents to form tertiary alcohols, with acid chlorides being more reactive than esters.
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Synthesis of Alcohols
The synthesis of alcohols from Grignard reagents involves nucleophilic addition to carbonyl compounds. When a Grignard reagent reacts with an acid chloride or ester, it forms a tetrahedral intermediate, which upon hydrolysis yields the corresponding alcohol. This method is particularly useful for constructing complex alcohols, such as dicyclohexylphenylmethanol, by carefully selecting the appropriate Grignard reagent and carbonyl compound.
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Related Practice
Textbook Question
A formate ester, such as ethyl formate, reacts with an excess of a Grignard reagent to give (after protonation) secondary alcohols with two identical alkyl groups.
(a) Propose a mechanism to show how the reaction of ethyl formate with an excess of allylmagnesium bromide gives, after protonation, hepta-1,6-dien-4-ol.
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Textbook Question
Propose a mechanism for the reaction of acetyl chloride with phenylmagnesium bromide to give 1,1-diphenylethanol.
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Textbook Question
Show how you would synthesize following tertiary alcohol by adding an appropriate Grignard reagent to a ketone.
d. 2-cyclopentylpentan-2-ol
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Textbook Question
A formate ester, such as ethyl formate, reacts with an excess of a Grignard reagent to give (after protonation) secondary alcohols with two identical alkyl groups.
(b) Show how you would use reactions of Grignard reagents with ethyl formate to synthesize the following secondary alcohols.
(i) pentan-3-ol
(ii) diphenylmethanol
(iii) trans,trans-nona-2,7-dien-5-ol
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Textbook Question
Show how you would synthesize the following alcohol by adding Grignard reagents to ethylene oxide.
(a) 2-phenylethanol
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