Textbook Question
Predict the products you would expect from the reaction of NaBH4 with the following compounds. You may assume that these reactions take place in methanol as the solvent.
(d)
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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 23c,d
Point out the flaws in the following incorrect Grignard syntheses.
(c) 
(d) 
Verified step by step guidance1
Step 1: Analyze the reaction in (c). The Grignard reagent, cyclohexylmagnesium bromide (C6H11MgBr), is reacting with acetone (CH3COCH3) under acidic conditions (H3O+). The expected product should involve the addition of the Grignard reagent to the carbonyl group of acetone, forming a tertiary alcohol. However, the product shown is incorrect.
Step 2: Identify the flaw in (c). The product depicted has a tertiary alcohol with an incorrect alkyl group attached to the carbon bearing the hydroxyl group. The Grignard reagent adds the cyclohexyl group to the carbonyl carbon, not the tert-butyl group shown in the product.
Step 3: Analyze the reaction in (d). The starting material is a cyclic ketone with a hydroxyl group (a hydroxy ketone). The Grignard reagent, ethylmagnesium bromide (CH3CH2MgBr), is expected to react with the ketone group, followed by acidic workup (H3O+). The product shown is incorrect.
Step 4: Identify the flaw in (d). The product depicted has two hydroxyl groups, one of which is attached to the carbon that originally had the ketone group. This is not possible because the Grignard reagent reacts with the ketone to form an alcohol, but it cannot introduce a second hydroxyl group at the same carbon.
Step 5: Conclude the analysis. In both cases, the Grignard reagent reacts with the carbonyl group to form an alcohol, but the products shown are inconsistent with the expected mechanism of Grignard reactions. The errors involve incorrect structural representations of the final products.
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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 to form carbon-carbon bonds. They are created by reacting an alkyl or aryl halide with magnesium metal in an anhydrous ether solvent. Understanding their reactivity and the conditions required for their formation is crucial for analyzing any synthetic pathway involving them.
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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 context of Grignard reactions, the Grignard reagent acts as a nucleophile, attacking carbonyl compounds to form alcohols. Recognizing the role of nucleophiles and electrophiles is essential for identifying flaws in synthetic routes.
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Reaction Conditions
The reaction conditions, including solvent choice, temperature, and the presence of moisture, are critical in organic reactions, particularly with Grignard reagents, which are sensitive to water. Any moisture can lead to the hydrolysis of Grignard reagents, rendering them ineffective. Understanding the importance of maintaining anhydrous conditions is vital for evaluating the success of Grignard syntheses.
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Related Practice
Textbook Question
Predict the products you would expect from the reaction of NaBH4 with the following compounds. You may assume that these reactions take place in methanol as the solvent.
(c) Ph-COOH
1647
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Textbook Question
Point out the flaws in the following incorrect Grignard syntheses.
(a)
1715
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Textbook Question
Predict the products you would expect from the reaction of NaBH4 with the following compounds. You may assume that these reactions take place in methanol as the solvent.
(a) CH3–(CH2)8–CHO
1704
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1
rank
Textbook Question
Predict the products of the following reactions.
(d)
(e)
901
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Textbook Question
Point out the flaws in the following incorrect Grignard syntheses.
(b)
1235
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