Textbook Question
Show how you would accomplish the following synthetic transformations. Show all intermediates.
j. trans-hex-2-ene → cis-hex-2-ene
1
views
Ch.9 - Alkynes
Wade9th EditionOrganic ChemistryISBN: 9780135213728
Not the one you use?Change textbookSelect a different textbook
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 35a,b
Show how you would synthesize the following compounds from acetylene and any other needed reagents:
(a) 6-phenylhex-1-en-4-yne
(b) cis-1-phenylpent-2-ene
Verified step by step guidance1
Step 1: Begin with acetylene (C₂H₂) as the starting material. To elongate the carbon chain, perform an alkylation reaction. First, deprotonate acetylene using a strong base like sodium amide (NaNH₂) to generate the acetylide ion. Then, react the acetylide ion with an appropriate alkyl halide (e.g., 1-bromobutane for part (a) and 1-bromopropane for part (b)) to add the desired carbon chain.
Step 2: For part (a), introduce the phenyl group. Use a second alkylation step by deprotonating the terminal alkyne again with NaNH₂ and reacting it with benzyl bromide (C₆H₅CH₂Br). This will attach the phenyl group to the chain. For part (b), the phenyl group can be introduced similarly, but ensure the chain length matches the target compound.
Step 3: To create the double bond in part (b), perform a partial hydrogenation of the alkyne using a Lindlar catalyst (Pd/CaCO₃, poisoned with quinoline). This will selectively reduce the alkyne to a cis-alkene. For part (a), retain the triple bond in the structure as required.
Step 4: For part (a), adjust the position of the triple bond and double bond as needed. Use hydroboration-oxidation (BH₃ followed by H₂O₂/NaOH) to convert the terminal alkyne into an alkene. Ensure the double bond is positioned correctly in the hex-1-en-4-yne structure.
Step 5: Verify the stereochemistry and connectivity of the final products. For part (b), ensure the cis configuration of the alkene is preserved. For part (a), confirm the phenyl group and the triple bond are correctly positioned in the 6-phenylhex-1-en-4-yne structure.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
4mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Alkyne Synthesis
Alkynes are hydrocarbons containing at least one carbon-carbon triple bond. They can be synthesized from simpler compounds like acetylene through various reactions, including elimination and coupling reactions. Understanding the mechanisms of these reactions is crucial for constructing more complex alkynes from simpler starting materials.
Recommended video:
Guided course
09:11
Alkyne Hydration
Electrophilic Addition Reactions
Electrophilic addition reactions involve the addition of electrophiles to nucleophilic sites in alkenes and alkynes. This concept is essential for synthesizing compounds like cis-1-phenylpent-2-ene, where the orientation of the addition can lead to different stereoisomers. Recognizing how to control regioselectivity and stereochemistry is vital in organic synthesis.
Recommended video:
Guided course
05:39Features of Addition Mechanisms.
Reagents and Reaction Conditions
The choice of reagents and reaction conditions significantly influences the outcome of organic reactions. For synthesizing the specified compounds, reagents such as bromine, lithium diisopropylamide (LDA), or Grignard reagents may be required. Understanding how these reagents interact with acetylene and other substrates is key to achieving the desired products.
Recommended video:
Guided course
01:52Reagents
Related Practice
Textbook Question
Predict the products formed when CH3CH2–C≡C:–Na+ reacts with the following compounds.
a. ethyl bromide
b. tert-butyl bromide
c. formaldehyde
5
views
Textbook Question
Show how you would accomplish the following synthetic transformations. Show all intermediates.
i. hex-1-yne → hexanal, CH3(CH2)4CHO
2
views
Textbook Question
Show how you would accomplish the following synthetic transformations. Show all intermediates.
h. hex-1-yne → hexan-2-one, CH3COCH2CH2CH2CH3
1
views
Textbook Question
Show how you would synthesize the following compounds, starting with acetylene and any compounds containing no more than four carbon atoms.
a. hex-1-yne
b. hex-2-yne
c. cis-hex-2-ene
1
views
Textbook Question
Predict the products formed when CH3CH2–C≡C:–Na+ reacts with the following compounds.
(d) cyclohexanone
(e) CH3CH2CH2CHO
1
views