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.
(e)
230
views
Ch. 7 - Structure and Synthesis of Alkenes; Elimination
Wade9th EditionOrganic ChemistryISBN: 9780135213728
Not the one you use?Change textbookSelect a different textbook
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 64b
Protonation converts the hydroxy group of an alcohol to a good leaving group. Suggest a mechanism for each reaction.
(b) 
Verified step by step guidance1
Step 1: Protonation of the alcohol group - The hydroxyl group (-OH) of the alcohol is protonated by sulfuric acid (H2SO4), converting it into a better leaving group (water, H2O). This occurs because the acidic environment provides a proton (H+), which attaches to the oxygen atom of the hydroxyl group.
Step 2: Formation of a carbocation - After protonation, the water molecule leaves, generating a carbocation intermediate. The stability of the carbocation is crucial, and in this case, the tertiary carbocation is formed due to the presence of three alkyl groups attached to the carbon, which stabilize the positive charge through hyperconjugation and inductive effects.
Step 3: Rearrangement of the carbocation - If necessary, the carbocation may undergo rearrangement to form a more stable carbocation. In this case, no rearrangement is needed as the tertiary carbocation is already highly stable.
Step 4: Elimination reaction - Heat promotes the elimination of a proton from a β-carbon (a carbon adjacent to the carbocation). This elimination leads to the formation of a double bond (alkene) in the product. The most stable alkene is formed, following Zaitsev's rule, which states that the more substituted alkene is favored.
Step 5: Final product formation - The reaction results in the formation of the cyclic alkene product, where the double bond is positioned in the most stable configuration within the ring structure.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
3mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Protonation of Alcohols
Protonation is the addition of a proton (H+) to a molecule, which in the case of alcohols, converts the hydroxy (-OH) group into a better leaving group, water (H2O). This process enhances the electrophilicity of the carbon atom bonded to the hydroxy group, facilitating subsequent reactions such as elimination or substitution.
Recommended video:
Guided course
01:01
How to name alcohols
Elimination Reactions
Elimination reactions involve the removal of a small molecule from a larger one, typically resulting in the formation of a double bond. In the context of alcohols, after protonation, the leaving group departs, and a β-hydrogen is often removed, leading to the formation of alkenes. This is a key step in dehydration reactions, commonly catalyzed by acids like sulfuric acid.
Recommended video:
Guided course
00:40Recognizing Elimination Reactions.
Mechanism of Acid-Catalyzed Reactions
The mechanism of acid-catalyzed reactions typically involves multiple steps, including protonation, formation of a carbocation, and elimination. In the provided reaction, sulfuric acid protonates the alcohol, forming a carbocation intermediate, which then undergoes elimination to yield an alkene. Understanding this mechanism is crucial for predicting the products and the reaction pathway.
Recommended video:
Guided course
06:34Acid-catalyzed hydration mechanism
Related Practice
Textbook Question
a. Design an alkyl halide that will give only 2,4-diphenylpent-2-ene upon treatment with potassium tert-butoxide (a bulky base that promotes E2 elimination).
b. What stereochemistry is required in your alkyl halide so that only the following stereoisomer of the product is formed?
845
views
Textbook Question
A chemist allows some pure (2S,3R)-3-bromo-2,3-diphenylpentane to react with a solution of sodium ethoxide (NaOCH2CH3) in ethanol. The products are two alkenes: A (cis-trans mixture) and B, a single pure isomer. Under the same conditions, the reaction of (2S,3S)-3-bromo-2,3-diphenylpentane gives two alkenes, A (cis-trans mixture) and C. Upon catalytic hydrogenation, all three of these alkenes (A, B, and C) give 2,3-diphenylpentane. Determine the structures of A, B, and C; give equations for their formation; and explain the stereospecificity of these reactions.
1654
views
Textbook Question
Pure (S)-2-bromo-2-fluorobutane reacts with methoxide ion in methanol to give a mixture of (S)-2-fluoro-2-methoxybutane and three fluoroalkenes.
a. Use mechanisms to show which three fluoroalkenes are formed.
2163
views
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.
(d)
250
views
Textbook Question
Protonation converts the hydroxy group of an alcohol to a good leaving group. Suggest a mechanism for each reaction.
(a)
998
views