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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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 39i
Bruice 8th EditionCh. 7 - The Reactions of Alkynes • An Introduction to Multistep SynthesisProblem 39iChapter 8, Problem 39i
What is the major product of the reaction of 1 mol of propyne with each of the following reagents?
i. sodium amide
Verified step by step guidance1
Step 1: Understand the structure of propyne. Propyne is an alkyne with the molecular formula C3H4. Its structure includes a triple bond between the first and second carbon atoms (CH≡C-CH3). The terminal hydrogen on the first carbon is acidic due to the sp hybridization of the carbon atom.
Step 2: Recognize the role of sodium amide (NaNH2) in the reaction. Sodium amide is a strong base that can deprotonate the acidic terminal hydrogen of propyne, forming a carbanion (acetylide ion). This reaction is a typical acid-base reaction.
Step 3: Write the chemical equation for the reaction. The reaction can be represented as: CH≡C-CH3 + NaNH2 → CH≡C⁻ + Na⁺ + NH3. Here, the acetylide ion (CH≡C⁻) is formed as the major product.
Step 4: Understand the significance of the acetylide ion. The acetylide ion is a nucleophile and can participate in further reactions, such as alkylation or addition reactions, depending on the reagents added subsequently.
Step 5: Note that no additional products are formed in this step unless further reagents are introduced. The major product of this reaction is the acetylide ion (CH≡C⁻), which is stabilized by the sodium cation (Na⁺).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Alkynes and Their Reactivity
Alkynes, such as propyne, are hydrocarbons containing at least one carbon-carbon triple bond. This triple bond makes alkynes more reactive than alkenes and alkanes, allowing them to undergo various reactions, including nucleophilic substitutions and eliminations. Understanding the reactivity of alkynes is crucial for predicting the products of their reactions with different reagents.
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Alkyne Hydration
Nucleophilic Substitution Reactions
Nucleophilic substitution reactions involve the replacement of a leaving group by a nucleophile. In the case of propyne reacting with sodium amide (NaNH2), the amide ion acts as a strong nucleophile, attacking the terminal carbon of the alkyne. This reaction can lead to the formation of an alkyne anion, which can further react with electrophiles to form new products.
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Formation of Alkynide Ions
When propyne reacts with sodium amide, it can generate an alkynide ion, which is a negatively charged species formed by deprotonation of the terminal hydrogen of the alkyne. This ion is highly reactive and can participate in further reactions, such as nucleophilic attacks on alkyl halides, leading to the formation of larger carbon chains. Recognizing the formation of alkynide ions is essential for predicting the major product of the reaction.
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Related Practice
Textbook Question
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
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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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1
rank
Textbook Question
Answer Problem 39 , parts a–h, using 2-butyne as the starting material instead of propyne.
c. Br2 (1 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
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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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