Textbook Question
Silver-assisted solvolysis of bromomethylcyclopentane in methanol gives a complex product mixture of the following five compounds. Propose mechanisms to account for these products.
(b)
Ch. 7 - Structure and Synthesis of Alkenes; Elimination
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 7, Problem 61b
Propose mechanisms for the following reactions. Additional products may be formed, but your mechanism only needs to explain the products shown.
(b) 
Verified step by step guidance1
Step 1: Protonation of the alcohol group - The reaction begins with the protonation of the hydroxyl group (-OH) on the cyclopentylmethanol molecule by sulfuric acid (H₂SO₄). This forms a good leaving group, water (H₂O), and converts the alcohol into a positively charged intermediate.
Step 2: Formation of a carbocation - The water molecule leaves, resulting in the formation of a carbocation at the benzylic position (the carbon attached to the cyclopentane ring). This carbocation is stabilized due to its proximity to the ring structure.
Step 3: Elimination to form alkenes - The carbocation undergoes elimination reactions to form the observed alkene products. A β-hydrogen is removed from adjacent carbons, leading to the formation of double bonds. This results in the formation of cyclopentene and methylenecyclopentane as products.
Step 4: Rearrangement to form cyclohexene - The carbocation can undergo a ring expansion via a hydride or alkyl shift, leading to the formation of a six-membered ring. This rearrangement results in the formation of cyclohexene as an additional product.
Step 5: Final products - The reaction yields three products: cyclopentene, methylenecyclopentane, and cyclohexene. These products are formed through elimination and rearrangement mechanisms facilitated by the acidic conditions and heat.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acid-Base Reactions
Acid-base reactions are fundamental in organic chemistry, where an acid donates a proton (H+) and a base accepts it. In the context of the given reaction involving H2SO4, a strong acid, understanding how protons are transferred is crucial for predicting the formation of products. This concept helps in identifying the reactive sites in molecules and the resulting changes in their structure.
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The Lewis definition of acids and bases.
Reaction Mechanisms
A reaction mechanism outlines the step-by-step sequence of elementary reactions that lead to the formation of products. It is essential to propose a mechanism for the reactions shown, as it provides insight into the intermediates formed and the transition states involved. Understanding mechanisms allows chemists to predict the outcome of reactions and the stability of intermediates.
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Thermal Decomposition
Thermal decomposition refers to the process where a compound breaks down into simpler substances when heated. In the context of the reaction with heat, recognizing how heat influences the stability of reactants and products is vital. This concept is particularly relevant for understanding how certain functional groups may rearrange or eliminate under heat, leading to the formation of multiple products.
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Related Practice
Textbook Question
Silver-assisted solvolysis of bromomethylcyclopentane in methanol gives a complex product mixture of the following five compounds. Propose mechanisms to account for these products.
(a)
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Textbook Question
Propose mechanisms for the following reactions. Additional products may be formed, but your mechanism only needs to explain the products shown.
(a)
2
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Textbook Question
E1 eliminations of alkyl halides are rarely useful for synthetic purposes because they give mixtures of substitution and elimination products. Explain why the sulfuric acid-catalyzed dehydration of cyclohexanol gives a good yield of cyclohexene even though the reaction goes by an E1 mechanism. (Hint: What are the nucleophiles in the reaction mixture? What products are formed if these nucleophiles attack the carbocation? What further reactions can these substitution products undergo?)
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Textbook Question
Show how you would convert (in one or two steps) 1-phenylpropane to the three products shown below. In each case, explain what unwanted reactions might produce undesirable impurities in the product.
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Textbook Question
Propose mechanisms for the following reactions. Additional products may be formed, but your mechanism only needs to explain the products shown.
(c)
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