Textbook Question
Show the products of the following acetylide alkylation reactions. [Make sure your product has the correct number of carbons.]
(c)
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Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
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Table of contents
- Ch. 2 - General Chemistry Translated: Finding the Electrons114
- Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis109
- Ch. 4 - Acids and Bases: Electron Flow144
- Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics118
- Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space112
- Ch. 7 - Principles of Green (Organic) Chemistry3
- Ch. 8 - Alkenes I: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes II: Oxidation and Reduction150
- Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions101
- Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions108
- Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes172
- Ch. 13 - Alcohols, Ethers and Related Compounds: Substitution and Elimination239
- Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution I: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution II: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems I: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems II: Pericyclic Reactions54
- Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring62
- Ch. 25 - Amines: Structure, Reactions, and Synthesis27
- Ch. 26 - Amino Acids, Proteins, and Peptide Synthesis9
- Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids54
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
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Mullins 1st EditionCh. 10 - Alkynes: Electrophilic Addition and Redox ReactionsProblem 45b
Mullins 1st EditionCh. 10 - Alkynes: Electrophilic Addition and Redox ReactionsProblem 45bChapter 9, Problem 45b
Show the products of the following acetylide alkylation reactions. [Make sure your product has the correct number of carbons.]
(b) 
Verified step by step guidance1
Step 1: Recognize that the reaction involves acetylide alkylation. The starting material is acetylene (H-C≡C-H), which will undergo deprotonation to form an acetylide ion.
Step 2: The first reagent, NaNH₂ (2 equivalents), is a strong base that will deprotonate both hydrogens on the acetylene molecule, forming the acetylide ion (C≡C²⁻). This ion is highly nucleophilic.
Step 3: The second reagent, bromocyclopentane (2 equivalents), is an alkyl halide. The acetylide ion will attack the carbon attached to the bromine in an SN2 reaction, displacing the bromine and forming a new carbon-carbon bond.
Step 4: Since 2 equivalents of bromocyclopentane are used, the acetylide ion will react twice, adding two cyclopentyl groups to the acetylene molecule. This results in a product with two cyclopentyl groups attached to the original triple bond.
Step 5: Verify the final product structure by ensuring the correct number of carbons and connectivity. The product will have a total of 12 carbons: 2 from the acetylene and 10 from the two cyclopentyl groups.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acetylide Ion Formation
Acetylide ions are formed by deprotonating terminal alkynes using strong bases like sodium amide (NaNH2). This reaction generates a nucleophilic acetylide ion, which can then participate in nucleophilic substitution reactions with alkyl halides, allowing for the formation of longer carbon chains.
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Nucleophilic Substitution Reactions
Nucleophilic substitution reactions involve the replacement of a leaving group (like bromine in the provided reaction) by a nucleophile (the acetylide ion). The mechanism can follow either an SN2 pathway, where the nucleophile attacks the electrophile directly, or an SN1 pathway, which involves the formation of a carbocation intermediate. The choice of mechanism depends on the structure of the substrate and the conditions of the reaction.
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Carbon Count in Organic Synthesis
In organic synthesis, it is crucial to account for the number of carbon atoms in the products. The reaction of an acetylide ion with an alkyl halide adds the carbon chain of the halide to the acetylide, thus increasing the total carbon count. Ensuring the correct number of carbons in the final product is essential for maintaining the integrity of the molecular structure and for further synthetic applications.
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Related Practice
Textbook Question
Show the products of the following acetylide alkylation reactions. [Make sure your product has the correct number of carbons.]
(a)
1083
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Textbook Question
For the alkynes shows here, show the product(s) expected to form when treated under the following conditions: (v) HCl (2 equiv.). If you expect two products, show both.
(c)
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Textbook Question
For the alkynes shows here, show the product(s) expected to form when treated under the following conditions: (ix) Br2 (2 equiv.). If you expect two products, show both.
(f)
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Textbook Question
Show the products of the following acetylide alkylation reactions. [Make sure your product has the correct number of carbons.]
(d)
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Textbook Question
Complete the following synthesis by providing the necessary reagents.
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