Textbook Question
Write a balanced equation for each reaction, showing the major product you expect.
(d)
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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 55f
Predict the dehydrohalogenation product(s) that result when the following alkyl halides are heated in alcoholic KOH. When more than one product is formed, predict the major and minor products.
(f) 
Verified step by step guidance1
Step 1: Analyze the structure of the given alkyl halide. The molecule is a bicyclic compound with two bromine atoms attached to adjacent carbons in a trans configuration. This setup is ideal for an E2 elimination reaction, as the anti-periplanar geometry is satisfied.
Step 2: Recall the mechanism of dehydrohalogenation in the presence of alcoholic KOH. The reaction proceeds via an E2 elimination mechanism, where a base abstracts a proton from a β-carbon, and the leaving group (Br) departs simultaneously, forming a double bond.
Step 3: Identify the β-hydrogens available for elimination. In this case, the β-hydrogens are located on the carbons adjacent to the carbons bearing the bromine atoms. The anti-periplanar geometry ensures that elimination can occur effectively.
Step 4: Predict the possible products. The elimination of HBr from either bromine atom can lead to the formation of two different alkenes. The double bond can form between the two carbons bearing the bromine atoms or between one of these carbons and a neighboring carbon.
Step 5: Determine the major and minor products. According to Zaitsev's rule, the more substituted alkene is generally the major product. Analyze the substitution pattern of the possible alkenes to predict which one will be the major product.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Dehydrohalogenation
Dehydrohalogenation is an elimination reaction where a hydrogen atom and a halogen atom (like bromine) are removed from adjacent carbon atoms in an alkyl halide, resulting in the formation of an alkene. This reaction typically occurs under basic conditions, such as with alcoholic KOH, which facilitates the removal of the halide and proton.
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03:02
The dehydrohalogenation mechanism.
Zaitsev's Rule
Zaitsev's Rule states that in elimination reactions, the more substituted alkene is usually the major product. This is because more substituted alkenes are generally more stable due to hyperconjugation and the inductive effect, leading to a preference for their formation over less substituted alkenes.
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01:18Defining Zaitsev’s Rule
Regioselectivity
Regioselectivity refers to the preference of a chemical reaction to yield one structural isomer over others when multiple products are possible. In the context of dehydrohalogenation, regioselectivity helps predict which alkene product will be favored based on the stability of the resulting double bond and the arrangement of substituents.
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05:09Heck Reaction
Related Practice
Textbook Question
Using cyclohexane as your starting material, show how you would synthesize each of the following compounds. (Once you have shown how to synthesize a compound, you may use it as the starting material in any later parts of this problem.)
a. bromocyclohexane
b. cyclohexene
c. ethoxycyclohexane
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Textbook Question
Predict the dehydrohalogenation product(s) that result when the following alkyl halides are heated in alcoholic KOH. When more than one product is formed, predict the major and minor products.
(a)
(b)
(c)
1
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Textbook Question
Predict the dehydrohalogenation product(s) that result when the following alkyl halides are heated in alcoholic KOH. When more than one product is formed, predict the major and minor products.
(d)
(e)
1
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Textbook Question
Show how you would prepare cyclopentene from each compound.
a. cyclopentanol
b. cyclopentyl bromide
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Textbook Question
Using cyclohexane as your starting material, show how you would synthesize each of the following compounds. (Once you have shown how to synthesize a compound, you may use it as the starting material in any later parts of this problem.)
d. 3-bromocyclohex-1-ene
e. cyclohexa-1,3-diene
f. cyclohexanol
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