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 39g,h
Bruice 8th EditionCh. 7 - The Reactions of Alkynes • An Introduction to Multistep SynthesisProblem 39g,hChapter 8, Problem 39g,h
What is the major product of the reaction of 1 mol of propyne with each of the following reagents?
g. excess H2, Pd/C
h. H2/Lindlar catalyst
Verified step by step guidance1
Step 1: Understand the structure of propyne. Propyne is an alkyne with the molecular formula C3H4. It contains a triple bond between the first and second carbon atoms (CH≡C-CH3).
Step 2: Analyze the reaction with excess H2 and Pd/C. In the presence of excess hydrogen gas (H2) and a palladium catalyst (Pd/C), the triple bond in propyne undergoes complete hydrogenation. This means the triple bond is reduced to a single bond, and all π bonds are replaced with σ bonds, resulting in a fully saturated alkane.
Step 3: Predict the product for excess H2 and Pd/C. The major product of this reaction is propane (CH3-CH2-CH3), as the triple bond is completely reduced to a single bond, and hydrogen atoms are added to the carbons involved in the triple bond.
Step 4: Analyze the reaction with H2 and Lindlar catalyst. The Lindlar catalyst is a poisoned catalyst that selectively reduces alkynes to alkenes without further reducing the alkene to an alkane. In this case, the triple bond in propyne is partially hydrogenated to form a cis-alkene.
Step 5: Predict the product for H2 and Lindlar catalyst. The major product of this reaction is cis-propene (CH3-CH=CH2), as the Lindlar catalyst ensures the addition of hydrogen atoms occurs on the same side of the molecule, resulting in a cis configuration.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Hydrogenation
Hydrogenation is a chemical reaction that involves the addition of hydrogen (H2) to unsaturated hydrocarbons, such as alkenes and alkynes, converting them into saturated hydrocarbons. In the context of propyne, hydrogenation can lead to the formation of propane when excess hydrogen is used, as it fully saturates the triple bond.
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The definition of hydrogenation.
Catalysts
Catalysts are substances that increase the rate of a chemical reaction without being consumed in the process. In the case of propyne reactions, palladium on carbon (Pd/C) is a common catalyst for complete hydrogenation, while Lindlar's catalyst, which is a poisoned palladium catalyst, selectively hydrogenates alkynes to cis-alkenes, preventing further reduction to alkanes.
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Alkyne Reactivity
Alkynes, characterized by their carbon-carbon triple bonds, exhibit unique reactivity patterns compared to alkenes and alkanes. They can undergo various reactions, including hydrogenation, where the triple bond can be converted to a double bond or a single bond, depending on the conditions and reagents used, influencing the final product formed in the reaction.
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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
What is the major product of the reaction of 1 mol of propyne with each of the following reagents?
d. Br2 (2 mol)/CH2Cl2
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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?
e. aqueous H2SO4, HgSO4
f. R2BH in THF followed by H2O2/HO− /H2O
Textbook Question
What is the major product of the reaction of 1 mol of propyne with each of the following reagents?
c. Br2 (1 mol)/CH2Cl2
1
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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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