Domanda del libro di testo
Show how you would accomplish the following synthetic transformations. Show all intermediates.
b. 2,2-dibromobutane → but-2-yne
1232
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Ch.9 - Alkynes
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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TOC.tableOfContents
- 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
Capitolo 9, Problema 33j,k,l
Predict the products of reaction of pent-1-yne with the following reagents.
j. NaNH2
k. H2SO4/HgSO4, H2O
l. Sia2BH, then H2O2, –OH
Guida verificata passo dopo passo1
Step 1: For part (j), when pent-1-yne reacts with NaNH₂, the strong base NaNH₂ deprotonates the terminal alkyne. This results in the formation of a negatively charged acetylide ion (C≡C⁻). The reaction can be represented as: .
Step 2: For part (k), when pent-1-yne reacts with H₂SO₄/HgSO₄ and H₂O, this is an example of an acid-catalyzed hydration reaction. The alkyne undergoes Markovnikov addition of water, where the OH group adds to the more substituted carbon, and the H adds to the less substituted carbon. This forms an enol intermediate, which tautomerizes to a ketone. The product is pentan-2-one.
Step 3: For part (l), when pent-1-yne reacts with Sia₂BH (disiamylborane), followed by H₂O₂ and OH⁻, this is an example of hydroboration-oxidation. The reaction proceeds with anti-Markovnikov addition of water, where the OH group adds to the less substituted carbon, and the H adds to the more substituted carbon. The enol intermediate formed tautomerizes to an aldehyde. The product is pentanal.
Step 4: Summarize the products for each reaction: (j) acetylide ion (C≡C⁻), (k) pentan-2-one, and (l) pentanal. Each reaction demonstrates a different type of reactivity of alkynes: deprotonation, Markovnikov hydration, and anti-Markovnikov hydration.
Step 5: To confirm your understanding, review the mechanisms for each reaction type: (1) deprotonation of terminal alkynes, (2) acid-catalyzed hydration with tautomerization, and (3) hydroboration-oxidation with tautomerization. This will help reinforce the concepts and ensure you can apply them to similar problems.
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Alkyne Reactivity
Alkynes, such as pent-1-yne, are hydrocarbons with at least one carbon-carbon triple bond. Their reactivity is significantly influenced by this triple bond, allowing them to undergo various reactions, including nucleophilic substitutions and additions. Understanding how alkynes react with different reagents is crucial for predicting the products of these reactions.
Video consigliato:
09:11
Alkyne Hydration
Hydroboration-Oxidation
Hydroboration-oxidation is a two-step reaction process used to convert alkynes into alcohols. In the first step, the alkyne reacts with diborane (Sia2BH) to form an organoborane intermediate. The second step involves oxidation with hydrogen peroxide and a base, resulting in the formation of an alcohol. This method is particularly useful for producing anti-Markovnikov alcohols.
Video consigliato:
06:38General properties of hydroboration-oxidation.
Acid-Catalyzed Hydration
Acid-catalyzed hydration of alkynes involves the addition of water across the triple bond in the presence of an acid catalyst, typically sulfuric acid and mercury(II) sulfate. This reaction leads to the formation of ketones or aldehydes, depending on the structure of the alkyne. The mechanism involves the formation of a vinyl cation, which is then attacked by water, highlighting the importance of regioselectivity in product formation.
Video consigliato:
06:34Acid-catalyzed hydration mechanism
Pratica correlata
Domanda del libro di testo
Predict the products of reaction of pent-1-yne with the following reagents.
g. cold, dilute KMnO4
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Domanda del libro di testo
Show how you would accomplish the following synthetic transformations. Show all intermediates.
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Show how you would accomplish the following synthetic transformations. Show all intermediates.
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Predict the products of reaction of pent-1-yne with the following reagents.
d. H2, Pd/BaSO4, quinoline
e. 1 equivalent of Br2
f. 2 equivalents of Br2
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Domanda del libro di testo
Predict the products of reaction of pent-1-yne with the following reagents.
a. 1 equivalent of HCl
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c. excess H2, Ni
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