Textbook Question
Show how you would accomplish the following synthetic transformations. Show all intermediates.
g. cyclodecyne → trans-cyclodecene
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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 34i
Show how you would accomplish the following synthetic transformations. Show all intermediates.
i. hex-1-yne → hexanal, CH3(CH2)4CHO
Verified step by step guidance1
Step 1: Analyze the transformation. The starting material is hex-1-yne, an alkyne, and the product is hexanal, an aldehyde. This indicates that the triple bond in hex-1-yne must be converted into a single bond, and the terminal carbon must be oxidized to form the aldehyde functional group.
Step 2: Select the appropriate reaction. To convert a terminal alkyne into an aldehyde, hydroboration-oxidation is a suitable method. This involves two steps: (a) hydroboration using a reagent like disiamylborane (R2BH) or 9-BBN, and (b) oxidation using hydrogen peroxide (H2O2) in a basic solution (NaOH).
Step 3: Perform hydroboration. Add disiamylborane (R2BH) to hex-1-yne. The boron atom selectively adds to the less substituted carbon of the triple bond, forming an organoborane intermediate.
Step 4: Oxidize the organoborane intermediate. Treat the organoborane with hydrogen peroxide (H2O2) in the presence of a base (NaOH). This step converts the boron-attached carbon into an aldehyde group, yielding hexanal.
Step 5: Verify the product. The final product is hexanal, CH3(CH2)4CHO, which matches the desired transformation. Ensure all intermediates and reagents are accounted for in the mechanism.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Alkyne Hydroboration-Oxidation
This reaction involves the addition of borane (BH3) to an alkyne, followed by oxidation with hydrogen peroxide (H2O2) in the presence of a base. For hex-1-yne, this process converts the terminal alkyne into an aldehyde, specifically hexanal, by forming a trialkyl borane intermediate that is subsequently oxidized.
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06:38
General properties of hydroboration-oxidation.
Markovnikov's Rule
Markovnikov's Rule states that in the addition of HX to an alkene or alkyne, the hydrogen atom will attach to the carbon with the greater number of hydrogen atoms already attached. This principle is crucial in predicting the formation of intermediates during the hydroboration of hex-1-yne, leading to the correct regioselectivity in the final product, hexanal.
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Synthetic Pathways and Intermediates
Understanding synthetic pathways involves recognizing the sequence of reactions and intermediates that lead from a starting material to a desired product. In this case, identifying the intermediates formed during the hydroboration and subsequent oxidation steps is essential for illustrating the transformation of hex-1-yne to hexanal.
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Related Practice
Textbook Question
Show how you would accomplish the following synthetic transformations. Show all intermediates.
j. trans-hex-2-ene → cis-hex-2-ene
1244
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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
1021
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Textbook Question
Show how you would accomplish the following synthetic transformations. Show all intermediates.
f. cyclodecyne → cis-cyclodecene
1314
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Textbook Question
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
949
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Textbook Question
Show how you would accomplish the following synthetic transformations. Show all intermediates.
h. hex-1-yne → hexan-2-one, CH3COCH2CH2CH2CH3
1375
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