Textbook Question
What product is obtained from the reaction of each of the following alcohols with
a. H2CrO4?
1. 3-pentanol
2. 1-pentanol
3. 2-methyl-2-pentanol
Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds
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. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing CompoundsProblem 19b
Bruice 8th EditionCh. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing CompoundsProblem 19bChapter 11, Problem 19b
What stereoisomers are formed in the following reactions? Which stereoisomer is the major product?
b. the acid-catalyzed dehydration of 3,4-dimethyl-3-hexanol to 3,4-dimethyl-3-hexene
Verified step by step guidance1
Identify the reaction type: The problem involves the acid-catalyzed dehydration of an alcohol, which is an elimination reaction (E1 mechanism). This reaction typically proceeds through the formation of a carbocation intermediate, followed by the elimination of water to form an alkene.
Determine the structure of the starting material: The starting compound is 3,4-dimethyl-3-hexanol. The hydroxyl group (-OH) is attached to the third carbon of the hexane chain, and there are methyl groups on both the third and fourth carbons.
Analyze the carbocation intermediate: During the E1 mechanism, the hydroxyl group is protonated by the acid catalyst, converting it into a good leaving group (water). The departure of water forms a carbocation at the third carbon. This carbocation is tertiary, which is relatively stable. No rearrangement is expected because the carbocation is already in its most stable form.
Determine the possible stereoisomers: The elimination step involves the removal of a β-hydrogen from one of the adjacent carbons (C2 or C4). This can lead to the formation of two possible stereoisomers of 3,4-dimethyl-3-hexene: the E (trans) and Z (cis) isomers. The E isomer has the two largest groups on opposite sides of the double bond, while the Z isomer has them on the same side.
Predict the major product: According to Zaitsev's rule, the more substituted alkene is generally the major product. Additionally, the E (trans) isomer is typically more stable than the Z (cis) isomer due to reduced steric hindrance between substituents. Therefore, the E isomer of 3,4-dimethyl-3-hexene is expected to 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.
Stereoisomerism
Stereoisomerism refers to the phenomenon where compounds have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of their atoms. This can lead to different physical and chemical properties. In organic chemistry, stereoisomers can be classified into enantiomers and diastereomers, which are crucial for understanding the behavior of molecules in reactions.
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Determining when molecules are stereoisomers.
Acid-Catalyzed Dehydration
Acid-catalyzed dehydration is a reaction where an alcohol is converted into an alkene through the removal of a water molecule, facilitated by an acid. This process typically involves protonation of the alcohol, leading to the formation of a carbocation intermediate, which can rearrange and lose a proton to form the double bond. Understanding this mechanism is essential for predicting the stereoisomers formed.
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06:01General features of acid-catalyzed dehydration.
Zaitsev's Rule
Zaitsev's Rule states that in elimination reactions, the more substituted alkene is generally the major product. This is due to the stability of more substituted alkenes, which are favored because they have greater hyperconjugation and less steric strain. Applying this rule helps in determining which stereoisomer will be predominant in the dehydration of alcohols.
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Related Practice
Textbook Question
What alcohol would you treat with phosphorus oxychloride and pyridine to form each of the following alkenes?
a.
b.
Textbook Question
Propose a mechanism for each of the following reactions:
a.
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Textbook Question
What stereoisomers are formed in the following reactions? Which stereoisomer is the major product?
a. the acid-catalyzed dehydration of 1-pentanol to 2-pentene
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Textbook Question
Explain why the following alcohols, when heated with acid, form the same alkene.
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Textbook Question
If the compound shown in the margin is heated in the presence of H2SO4,
a. what constitutional isomer would be formed in greatest yield?
b. what stereoisomer would be formed in greater yield?
1
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