Textbook Question
Predict the products of the following reactions:
(e)
(f)
Ch. 18 - Ketones and Aldehydes
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 18, Problem 11d
Show how you would accomplish the following synthetic conversions. You may use any additional reagents and solvents you need.
(d) 
Verified step by step guidance1
Step 1: Begin with the starting material, benzaldehyde (PhCHO). To introduce the alkyne functionality, perform a nucleophilic addition reaction using ethynylmagnesium bromide (C≡CHMgBr), a Grignard reagent. This will add the ethynyl group to the carbonyl carbon, forming an alcohol intermediate.
Step 2: After the addition of the ethynyl group, the intermediate will be a secondary alcohol with the structure PhCH(OH)C≡CH. This step involves hydrolysis of the Grignard addition product using water or dilute acid.
Step 3: To extend the alkyne chain, perform an alkylation reaction. Deprotonate the terminal alkyne (C≡CH) using a strong base such as sodium amide (NaNH2) to generate the acetylide anion (C≡C⁻). Then, react this anion with ethyl bromide (CH3CH2Br) to introduce the ethyl group, forming PhCH(OH)C≡CCH2CH3.
Step 4: Ensure stereochemical integrity and verify the product structure. The hydroxyl group remains intact, and the alkyne chain is extended as desired. Use spectroscopic techniques like NMR or IR to confirm the presence of the alcohol and alkyne functionalities.
Step 5: Purify the final product using appropriate methods such as column chromatography or recrystallization to isolate PhCH(OH)C≡CCH2CH3 in high yield and purity.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Aldol Condensation
Aldol condensation is a key reaction in organic chemistry where aldehydes or ketones with alpha-hydrogens react in the presence of a base to form beta-hydroxy aldehydes or ketones. This reaction can lead to the formation of larger carbon skeletons through the formation of carbon-carbon bonds, which is essential for synthesizing complex molecules.
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Crossed Aldol
Alkyne Formation
The formation of alkynes typically involves the elimination of small molecules from alkenes or the dehydrohalogenation of alkyl halides. In this context, the conversion of a compound to an alkyne requires specific reagents, such as strong bases, to facilitate the removal of hydrogen or halogen atoms, resulting in the formation of a triple bond.
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Reagent Selection
Choosing the appropriate reagents and solvents is crucial in organic synthesis to ensure the desired reaction occurs efficiently. For the conversion of PhCHO to the target compound, reagents such as sodium hydroxide for aldol condensation and strong bases like sodium amide for alkyne formation may be necessary to achieve the desired transformations while controlling reaction conditions.
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Related Practice
Textbook Question
Sodium triacetoxyborohydride, NaBH(OAc)3, is a mild reducing agent that reduces aldehydes much more quickly than ketones. It can be used to reduce aldehydes in the presence of ketones, such as in the following reaction:
(b) Propose a mechanism for the reduction of an aldehyde by sodium triacetoxyborohydride.
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Textbook Question
Show how you would accomplish the following synthetic conversions. You may use any additional reagents and solvents you need.
(b)
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Textbook Question
Sodium triacetoxyborohydride, NaBH(OAc)3, is a mild reducing agent that reduces aldehydes much more quickly than ketones. It can be used to reduce aldehydes in the presence of ketones, such as in the following reaction:
(a) Draw a complete Lewis structure for sodium triacetoxyborohydride.
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Textbook Question
Show how you would accomplish the following synthetic conversions. You may use any additional reagents and solvents you need.
(a)
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Textbook Question
Propose mechanisms for
(a) the acid-catalyzed hydration of chloral to form chloral hydrate.
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