Textbook Question
What is the major product of the reaction of 1 mol of propyne with each of the following reagents?
i. sodium amide
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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 40c
Bruice 8th EditionCh. 7 - The Reactions of Alkynes • An Introduction to Multistep SynthesisProblem 40cChapter 8, Problem 40c
Answer Problem 39 , parts a–h, using 2-butyne as the starting material instead of propyne.
c. Br2 (1 mol)/CH2Cl2
Verified step by step guidance1
Identify the starting material: The starting material is 2-butyne, which is an alkyne with the structure CH3-C≡C-CH3. It contains a triple bond between the second and third carbons.
Understand the reagent: The reagent is Br2 (1 mol) in CH2Cl2. Bromine (Br2) is a halogen that reacts with alkynes to add across the triple bond. The solvent, CH2Cl2 (dichloromethane), is inert and does not participate in the reaction.
Determine the reaction type: This is a halogenation reaction. When 1 mol of Br2 is used with an alkyne, it adds across the triple bond to form a dihaloalkene (a compound with two bromine atoms and a double bond).
Predict the product: The triple bond in 2-butyne will react with 1 mol of Br2 to form (E)-2,3-dibromo-2-butene. The addition of bromine is typically anti-addition, meaning the bromine atoms will add to opposite sides of the double bond, resulting in the trans (E) isomer.
Write the reaction mechanism: The reaction proceeds via the formation of a bromonium ion intermediate. The triple bond attacks Br2, forming a cyclic bromonium ion. Then, the second bromine ion (Br⁻) attacks the more substituted carbon of the bromonium ion, leading to the anti-addition product.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Alkyne Reactivity
Alkynes, such as 2-butyne, are hydrocarbons with a carbon-carbon triple bond. This triple bond makes them more reactive than alkenes and alkanes, allowing them to undergo various addition reactions. Understanding the reactivity of alkynes is crucial for predicting the products formed when they react with halogens like Br2.
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Alkyne Hydration
Electrophilic Addition
Electrophilic addition is a fundamental reaction mechanism in organic chemistry where an electrophile reacts with a nucleophile, leading to the formation of a more stable product. In the case of 2-butyne reacting with Br2, the triple bond acts as a nucleophile, attacking the electrophilic bromine molecule, resulting in the addition of bromine across the triple bond.
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Solvent Effects
The choice of solvent can significantly influence the outcome of a chemical reaction. In this case, CH2Cl2 (dichloromethane) is a polar aprotic solvent that can stabilize the transition state during the electrophilic addition of Br2 to 2-butyne. Understanding solvent effects is essential for optimizing reaction conditions and predicting product distributions.
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Related Practice
Textbook Question
Answer Problem 39, parts a–h, using 2-butyne as the starting material instead of propyne.
a. HBr (1 mol)
b. HBr (2 mol)
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Textbook Question
Answer Problem 39 , parts a–h, using 2-butyne as the starting material instead of propyne.
d. Br2 (2 mol)/CH2Cl2
1
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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
What is the major product of the reaction of 1 mol of propyne with each of the following reagents?
j. the product of part i followed by 1-chloropropane
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Textbook Question
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
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