Textbook Question
Answer Problem 39 , parts a–h, using 2-butyne as the starting material instead of propyne.
d. Br2 (2 mol)/CH2Cl2
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Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
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Bruice 8th EditionCh. 7 - The Reactions of Alkynes • An Introduction to Multistep SynthesisProblem 40f
Bruice 8th EditionCh. 7 - The Reactions of Alkynes • An Introduction to Multistep SynthesisProblem 40fChapter 8, Problem 40f
Answer Problem 39, parts a–h, using 2-butyne as the starting material instead of propyne.
f. R2BH in THF followed by H2O2/HO− /H2O
Verified step by step guidance1
Identify the starting material, 2-butyne, which is an alkyne with the structure CH≡C-CH2-CH3. The triple bond is located between the first and second carbons.
Understand the reagents: R2BH in THF is a hydroboration reagent that adds a boron atom and a hydrogen atom across the triple bond in a syn-addition manner. This step converts the alkyne into a trialkylborane intermediate.
Recognize the second step: H2O2/HO−/H2O is used to oxidize the trialkylborane intermediate into an enol. The enol then tautomerizes to form a carbonyl compound (a ketone or aldehyde).
Determine regioselectivity: Hydroboration-oxidation of terminal alkynes typically leads to the formation of aldehydes, while internal alkynes like 2-butyne yield ketones. The boron adds to the less substituted carbon of the triple bond, following anti-Markovnikov selectivity.
Conclude the product: The reaction of 2-butyne with R2BH followed by H2O2/HO−/H2O will result in the formation of a ketone, specifically 2-butanone, due to the internal alkyne structure and the regioselectivity of the reaction.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Hydroboration-Oxidation
Hydroboration-oxidation is a two-step reaction process used to convert alkenes and alkynes into alcohols. In the first step, a borane reagent (like R2BH) adds across the triple bond of the alkyne, forming a trialkylborane intermediate. The second step involves oxidation with hydrogen peroxide and a base, which replaces the boron with a hydroxyl group, yielding an alcohol. This method is notable for its anti-Markovnikov selectivity.
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General properties of hydroboration-oxidation.
Alkyne Reactivity
Alkynes, characterized by their carbon-carbon triple bonds, exhibit unique reactivity compared to alkenes and alkanes. They can undergo various reactions, including addition reactions, where reagents add across the triple bond. The reactivity of alkynes is influenced by their hybridization and the presence of electron-withdrawing groups, making them versatile intermediates in organic synthesis.
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Regioselectivity
Regioselectivity refers to the preference of a chemical reaction to yield one structural isomer over others when multiple possibilities exist. In the context of hydroboration-oxidation, the reaction is regioselective, favoring the formation of the less substituted alcohol due to the mechanism of boron addition. Understanding regioselectivity is crucial for predicting the outcome of reactions involving unsaturated hydrocarbons.
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Related Practice
Textbook Question
Answer Problem 39, parts a–h, using 2-butyne as the starting material instead of propyne.
h. H2/Lindlar catalyst
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Textbook Question
Answer Problem 39 , parts a–h, using 2-butyne as the starting material instead of propyne.
c. Br2 (1 mol)/CH2Cl2
2
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Textbook Question
Answer Problem 39, parts a–h, using 2-butyne as the starting material instead of propyne.
e. aqueous H2SO4, HgSO4
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Textbook Question
Answer Problem 39, parts a–h, using 2-butyne as the starting material instead of propyne.
g. excess H2, Pd/C
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Textbook Question
What is each compound's systematic name?
a. CH3C☰CCH2CH2CH2CH═CH2
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