Textbook Question
Show how you would convert
a. oct-3-yne to cis-oct-3-ene.
b. pent-2-yne to trans-pent-2-ene.
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Ch.9 - Alkynes
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 9, Problem 9
Show how you would synthesize 2-phenylhex-3-yn-2-ol, starting with acetophenone (PhCOCH3) and any other reagents you need. ("2-ol" means there is an OH group on C2.)
Verified step by step guidance1
Step 1: Begin with acetophenone (PhCOCH3). Perform an alkylation reaction to introduce a hexynyl group at the alpha position. Use a strong base like NaNH2 to deprotonate the alpha hydrogen of acetophenone, forming an enolate ion. Then, react this enolate with 1-bromo-3-hexyne to attach the hexynyl group.
Step 2: After the alkylation, you will have 2-phenylhex-3-yn-2-one. To convert the ketone group into an alcohol group, perform a reduction reaction. Use a reducing agent such as NaBH4 (sodium borohydride) or LiAlH4 (lithium aluminum hydride) to selectively reduce the ketone to a secondary alcohol.
Step 3: Ensure stereoselectivity during the reduction step if necessary, as the product is 2-phenylhex-3-yn-2-ol. The reducing agent will add a hydrogen atom to the carbonyl carbon, forming the alcohol group.
Step 4: Purify the product using techniques such as recrystallization or column chromatography to isolate 2-phenylhex-3-yn-2-ol from any side products or unreacted reagents.
Step 5: Confirm the structure of the synthesized compound using spectroscopic methods such as NMR (nuclear magnetic resonance) and IR (infrared spectroscopy) to verify the presence of the alcohol group (-OH) and the alkyne (-C≡C-) functionality.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Alkyne Synthesis
Alkyne synthesis involves the formation of carbon-carbon triple bonds, which can be achieved through various methods such as elimination reactions or coupling reactions. In this case, the synthesis of 2-phenylhex-3-yn-2-ol requires the introduction of a triple bond at the correct position in the carbon chain, which can be accomplished using reagents like sodium amide or alkyl halides.
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Alkyne Hydration
Nucleophilic Addition to Carbonyls
Nucleophilic addition to carbonyl compounds, such as acetophenone, is a fundamental reaction in organic chemistry. In this process, a nucleophile attacks the electrophilic carbon of the carbonyl group, leading to the formation of an alcohol. This step is crucial for synthesizing the desired alcohol functional group in 2-phenylhex-3-yn-2-ol.
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Functional Group Interconversion
Functional group interconversion refers to the transformation of one functional group into another, which is essential in organic synthesis. In this synthesis, converting the ketone group of acetophenone into an alcohol group is necessary. This can be achieved through reduction reactions, such as using lithium aluminum hydride (LiAlH4), to facilitate the conversion while maintaining the overall structure of the molecule.
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Related Practice
Textbook Question
When 2,2-dibromo-1-phenylpropane is heated overnight with sodium amide at 150°C, the major product (after addition of water) is a different foul-smelling compound of formula C9H8. Propose a structure for this product, and give a mechanism to account for its formation.
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Textbook Question
Show how you would synthesize each compound, beginning with acetylene and any necessary additional reagents
(a)
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Textbook Question
When 2,2-dibromo-1-phenylpropane is heated overnight in fused KOH at 200 C, the major product is a foul-smelling compound of formula C9H8. Propose a structure for this product, and give a mechanism to account for its formation.
Problem-Solving Hint:
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Textbook Question
Show how you would synthesize each compound, beginning with acetylene and any necessary additional reagents
(c)
(d)
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Textbook Question
Show how you would synthesize each compound, beginning with acetylene and any necessary additional reagents
(b)
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