Textbook Question
Which of following ethers cannot be made by a Williamson ether synthesis?
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Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides
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. 9 - Substitution and Elimination Reactions of Alkyl HalidesProblem 96d
Bruice 8th EditionCh. 9 - Substitution and Elimination Reactions of Alkyl HalidesProblem 96dChapter 10, Problem 96d
For each of the following alkyl halides, indicate the stereoisomer that would be obtained in greatest yield in an E2 reaction.
d. 3-bromo-3,4-dimethylhexane
Verified step by step guidance1
Identify the substrate: The given compound is 3-bromo-3,4-dimethylhexane, which is a tertiary alkyl halide. Tertiary alkyl halides are highly favorable for E2 elimination reactions due to steric hindrance that disfavors substitution reactions.
Recall the E2 mechanism: E2 elimination is a one-step concerted reaction where a base abstracts a β-hydrogen (hydrogen on a carbon adjacent to the carbon bearing the leaving group), and the leaving group (in this case, bromine) departs simultaneously, forming a double bond.
Determine the β-hydrogens: In 3-bromo-3,4-dimethylhexane, the β-carbons are the carbons adjacent to the carbon bonded to the bromine (C-3). These are C-2 and C-4. Examine the hydrogens on these β-carbons to identify possible elimination sites.
Apply anti-periplanar geometry: For the E2 reaction to proceed, the β-hydrogen and the leaving group (bromine) must be in an anti-periplanar (coplanar but opposite) arrangement. Analyze the Newman projection or the 3D structure of the molecule to determine which β-hydrogen satisfies this geometric requirement.
Predict the major product: The major product of the E2 reaction will be the most stable alkene, which is typically the more substituted alkene (Zaitsev's rule). Compare the possible alkenes formed by elimination at C-2 and C-4, and identify the stereoisomer with the greatest yield based on stability and anti-periplanar geometry.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
E2 Reaction Mechanism
The E2 (bimolecular elimination) reaction is a concerted process where a base abstracts a proton while a leaving group departs, resulting in the formation of a double bond. This mechanism typically requires a strong base and is stereospecific, favoring the formation of the more stable alkene. Understanding the stereochemistry involved is crucial for predicting the major product.
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09:36
Drawing the E2 Mechanism.
Stereochemistry and Alkene Stability
Stereochemistry refers to the spatial arrangement of atoms in molecules, which significantly influences the stability of alkenes. In E2 reactions, the formation of trans alkenes is generally favored over cis due to reduced steric strain. Recognizing the stereochemical outcomes helps in determining which isomer will be produced in greater yield.
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04:28Understanding trends of alkene stability.
Substituent Effects on Elimination Reactions
The presence and position of substituents on the alkyl halide can greatly affect the outcome of E2 reactions. Bulky groups near the leaving group can hinder the approach of the base, while more substituted alkenes are typically more stable due to hyperconjugation and inductive effects. Analyzing the structure of 3-bromo-3,4-dimethylhexane is essential to predict the major product.
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Related Practice
Textbook Question
For each of the following alkyl halides, indicate the stereoisomer that would be obtained in greatest yield in an E2 reaction.
c. 3-bromo-2,3-dimethylpentane
d. 3-bromo-3,4-dimethylhexane
Textbook Question
For each of the following alkyl halides, indicate the stereoisomer that would be obtained in greatest yield in an E2 reaction.
a. 3-bromo-2,2,3-trimethylpentane
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Textbook Question
What are the products of the following reactions?
a.
b.
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Textbook Question
When 2-bromo-2,3-dimethylbutane reacts with a strong base, two alkenes (2,3-dimethyl-1-butene and 2,3-dimethyl-2-butene) are formed.
a. Which of the bases (A, B, C, or D) would form the highest percentage of the 1-alkene?
b. Which would give the highest percentage of the 2-alkene?
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Textbook Question
For each of the following alkyl halides, indicate the stereoisomer that would be obtained in greatest yield in an E2 reaction.
b. 4-bromo-2,2,3,3-tetramethylpentane
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