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)
3
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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 40d
Bruice 8th EditionCh. 7 - The Reactions of Alkynes • An Introduction to Multistep SynthesisProblem 40dChapter 8, Problem 40d
Answer Problem 39 , parts a–h, using 2-butyne as the starting material instead of propyne.
d. Br2 (2 mol)/CH2Cl2
Verified step by step guidance1
Identify the starting material: The starting material is 2-butyne, which is a terminal alkyne with the structure CH3-C≡C-CH3.
Understand the reagent: The reagent is Br2 (2 mol) in CH2Cl2. Bromine (Br2) in an inert solvent like dichloromethane (CH2Cl2) is used to add bromine atoms across the triple bond of the alkyne.
Determine the reaction type: This is a halogenation reaction. When an alkyne reacts with 2 equivalents of Br2, the triple bond is fully saturated, resulting in a tetrahalide product.
Write the reaction mechanism: In the first step, one equivalent of Br2 adds across the triple bond, converting it into a dibromoalkene (CH3-CBr=CHBr-CH3). In the second step, the remaining equivalent of Br2 adds across the double bond, resulting in a tetrahalide (CH3-CBr2-CBr2-CH3).
Verify the product: The final product is 2,2,3,3-tetrabromobutane, where all four bromine atoms are added to the original carbon atoms of the triple bond.
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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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Electrophilic Addition
Electrophilic addition is a fundamental reaction mechanism in organic chemistry where an electrophile reacts with a nucleophile, resulting in the formation of a more saturated compound. In the case of 2-butyne reacting with Br2, the triple bond acts as a nucleophile, attacking the electrophilic bromine, leading to the formation of a dibrominated product.
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Stereochemistry of Addition Reactions
Stereochemistry refers to the spatial arrangement of atoms in molecules and how this affects their chemical behavior. When Br2 adds to 2-butyne, the stereochemical outcome can lead to different isomers, such as cis and trans forms, depending on the reaction conditions. Understanding stereochemistry is essential for predicting the specific products and their configurations in addition reactions.
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Related Practice
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
2
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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
2
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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
5
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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
2
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