Textbook Question
Develop syntheses for the following compounds. As starting materials, you may use cyclopentanol, alcohols containing no more than four carbon atoms, and any common reagents and solvents.
(b) 1-chloro-1-ethylcyclopentane
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Ch.11 - Reactions of Alcohols
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 11, Problem 37b
To practice working through the early parts of a multistep synthesis, devise syntheses of
(b) 3-ethylpentan-2-one from compounds containing no more than three carbon atoms.
Verified step by step guidance1
Step 1: Begin by identifying the target molecule, 3-ethylpentan-2-one. It is a ketone with a five-carbon chain and an ethyl group attached to the third carbon. The goal is to synthesize this molecule using starting materials with no more than three carbon atoms.
Step 2: Plan the synthesis by breaking down the target molecule into smaller fragments. Notice that the molecule can be constructed by combining a three-carbon fragment (propyl group) and a two-carbon fragment (ethyl group). Consider using an aldol condensation reaction to form the carbon-carbon bond between these fragments.
Step 3: Select appropriate starting materials. For the three-carbon fragment, use propanal (CH₃CH₂CHO), which contains an aldehyde functional group. For the two-carbon fragment, use ethyl acetate (CH₃COOCH₂CH₃), which contains an ester functional group. Both starting materials meet the requirement of containing no more than three carbon atoms.
Step 4: Perform an aldol condensation reaction. First, generate the enolate ion from ethyl acetate by treating it with a strong base such as sodium ethoxide (NaOEt). The enolate ion will act as a nucleophile and attack the carbonyl carbon of propanal, forming a β-hydroxyketone intermediate.
Step 5: Dehydrate the β-hydroxyketone intermediate to form the α,β-unsaturated ketone. Then, perform hydrogenation (reduction) using a catalyst like palladium on carbon (Pd/C) to reduce the double bond, yielding 3-ethylpentan-2-one as the final product.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Multistep Synthesis
Multistep synthesis involves a series of chemical reactions that transform starting materials into a desired product through intermediate compounds. Understanding this concept is crucial for planning synthetic routes, as it requires knowledge of reaction mechanisms, functional group transformations, and the ability to strategize the sequence of reactions to achieve the target molecule efficiently.
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Multistep Synthesis
Carbon Skeleton and Functional Groups
The carbon skeleton refers to the arrangement of carbon atoms in a molecule, which determines its structure and reactivity. In this question, recognizing how to manipulate a carbon skeleton with no more than three carbon atoms to build up to 3-ethylpentan-2-one is essential. Additionally, understanding functional groups and their reactivity will guide the selection of appropriate reactions to introduce necessary features into the molecule.
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02:36Identifying Functional Groups
Reagents and Reaction Conditions
Different reagents and reaction conditions can significantly influence the outcome of a chemical reaction. Knowledge of which reagents can facilitate specific transformations, such as alkylation or oxidation, is vital for devising a successful synthesis. Additionally, understanding the conditions under which these reactions occur, such as temperature and solvent choice, is important for optimizing yields and minimizing side reactions.
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Related Practice
Textbook Question
To practice working through the early parts of a multistep synthesis, devise syntheses of
(a) pentan-3-one from alcohols containing no more than three carbon atoms.
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Textbook Question
A student wanted to use the Williamson ether synthesis to make (R)-2-ethoxybutane. He remembered that the Williamson synthesis involves an SN2 displacement, which takes place with inversion of configuration. He ordered a bottle of (S)-butan-2-ol for his chiral starting material. He also remembered that the SN2 goes best on primary halides and tosylates, so he made ethyl tosylate and sodium (S)-but-2-oxide. After warming these reagents together, he obtained an excellent yield of 2-ethoxybutane.
a. What enantiomer of 2-ethoxybutane did he obtain? Explain how this enantiomer results from the SN2 reaction of ethyl tosylate with sodium (S)-but-2-oxide.
b. What would have been the best synthesis of (R)-2-ethoxybutane?
c. How can this student convert the rest of his bottle of (S)-butan-2-ol to (R)-2-ethoxybutane?
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Textbook Question
Develop syntheses for the following compounds. As starting materials, you may use cyclopentanol, alcohols containing no more than four carbon atoms, and any common reagents and solvents.
(c)
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Textbook Question
Phenols (pKa ≈ 10) are more acidic than other alcohols, so they are easily deprotonated by sodium hydroxide or potassium hydroxide. The anions of phenols (phenoxide ions) can be used in the Williamson ether synthesis, especially with very reactive alkylating reagents such as dimethyl sulfate. Using phenol, dimethyl sulfate, and other necessary reagents, show how you would synthesize methyl phenyl ether.
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Textbook Question
Develop syntheses for the following compounds. As starting materials, you may use cyclopentanol, alcohols containing no more than four carbon atoms, and any common reagents and solvents.
(a) trans-cyclopentane-1,2-diol
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