Textbook Question
Make models of the following compounds, and predict the products formed when they react with the strong bases shown.
(b) meso-1,2-dibromo-1,2-diphenylethane + (CH3CH2)3N:
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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 27d
Make models of the following compounds, and predict the products formed when they react with the strong bases shown.
(d) 
Verified step by step guidance1
Step 1: Identify the type of reaction. The presence of NaOH in acetone suggests that this is an E2 elimination reaction, which typically occurs with strong bases and favors anti-coplanar geometry.
Step 2: Analyze the structure of the substrate. The molecule is a bicyclic compound with a chlorine atom attached to a carbon. The hydrogen atom on the adjacent carbon is positioned anti-coplanar to the chlorine atom, which is a requirement for E2 elimination.
Step 3: Determine the leaving group and the proton to be abstracted. In this case, the chlorine atom is the leaving group, and the base (NaOH) will abstract the anti-coplanar hydrogen from the adjacent carbon.
Step 4: Predict the product of the elimination. The removal of the hydrogen and chlorine will result in the formation of a double bond between the two carbons involved in the elimination. The bicyclic structure will remain intact, but a new alkene will be formed.
Step 5: Consider stereochemistry and regioselectivity. Since anti-coplanar geometry is required, the elimination will occur in a specific direction dictated by the spatial arrangement of the substituents. Ensure the double bond is placed correctly in the bicyclic structure.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
E2 Elimination Mechanism
The E2 elimination mechanism is a concerted reaction where a strong base abstracts a proton from a β-carbon while a leaving group departs from the α-carbon, resulting in the formation of a double bond. This mechanism requires the hydrogen and leaving group to be anti-coplanar, meaning they must be on opposite sides of the molecule, which facilitates the elimination process.
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Drawing the E2 Mechanism.
Anti-Coplanar vs. Syn-Coplanar
In E2 reactions, anti-coplanar arrangements are preferred because they allow for optimal orbital overlap during the transition state, leading to more stable products. Syn-coplanar arrangements, where the hydrogen and leaving group are on the same side, are less common and typically occur when free rotation around the bond is restricted, such as in cyclic compounds.
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Role of Strong Bases
Strong bases, like NaOH, are crucial in E2 reactions as they effectively deprotonate the β-hydrogen, facilitating the elimination of the leaving group. The choice of solvent, such as acetone, can also influence the reaction pathway and product distribution, as polar aprotic solvents can stabilize the transition state and enhance the reactivity of the base.
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Related Practice
Textbook Question
Make models of the following compounds, and predict the products formed when they react with the strong bases shown.
(c) (d,l)-1,2-dibromo-1,2-diphenylethane + (CH3CH2)3N:
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Textbook Question
When the following stereoisomer of 2-bromo-1,3-dimethylcyclohexane is treated with sodium methoxide, no E2 reaction is observed. Explain why this compound cannot undergo the E2 reaction in the chair conformation.
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Textbook Question
Predict the elimination products of the following reactions, and label the major products.
b. trans-1-bromo-2-methylcyclohexane + NaOCH3 in CH3OH
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Textbook Question
Make models of the following compounds, and predict the products formed when they react with the strong bases shown.
(a)
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Textbook Question
Predict the elimination products of the following reactions, and label the major products.
a. cis-1-bromo-2-methylcyclohexane + NaOCH3 in CH3OH
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