Textbook Question
Show how the following ketones might be synthesized from the indicated acids, using any necessary reagents.
(a) propiophenone from propionic acid (using alkylation of the acid)
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Ch. 20 - Carboxylic Acids
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 20, Problem 20b
Draw the following sugars using Haworth projections:
b. α-D-tagatopyranose
Verified step by step guidance1
Understand the problem: You are tasked with drawing the Haworth projection of α-D-tagatopyranose. This involves converting the sugar from its Fischer projection to its cyclic (Haworth) form, specifically in the pyranose (six-membered ring) form.
Step 1: Identify the structure of D-tagatose in its Fischer projection. D-tagatose is a ketohexose, meaning it has six carbons and a ketone group at the second carbon. The hydroxyl groups (-OH) on carbons 3, 4, and 5 are arranged as follows: left, right, and right, respectively, in the Fischer projection.
Step 2: Cyclize the sugar into its pyranose form. The hydroxyl group on carbon 5 attacks the carbonyl carbon (C2, the ketone group) to form a six-membered ring. This creates a new chiral center at C2, which determines the α or β anomer. For the α-anomer, the newly formed hydroxyl group at C2 will point down in the Haworth projection.
Step 3: Draw the six-membered ring (pyranose) structure. Place oxygen as one of the ring atoms, and arrange the remaining carbons (C1 through C6) around the ring. Ensure that the substituents (hydroxyl groups and hydrogens) are placed correctly based on the Fischer projection. For D-sugars, the CH2OH group at C5 points up in the Haworth projection.
Step 4: Finalize the Haworth projection for α-D-tagatopyranose. Ensure that the hydroxyl group at C2 (the anomeric carbon) points down (α-anomer), and the other substituents are placed according to the stereochemistry of the original Fischer projection. Double-check the orientation of all groups to ensure accuracy.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Haworth Projections
Haworth projections are a way to represent the cyclic forms of sugars, particularly monosaccharides. They depict the sugar in a cyclic structure, showing the orientation of the hydroxyl groups and the anomeric carbon. This representation helps visualize the stereochemistry of the sugar, which is crucial for understanding its reactivity and interactions.
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Monosaccharides - Haworth Projections
Anomeric Carbon
The anomeric carbon is the carbon atom in a sugar that was the carbonyl carbon in its open-chain form. In cyclic sugars, it becomes a new stereocenter, leading to two possible configurations: alpha (α) and beta (β). The configuration of the anomeric carbon significantly influences the sugar's properties and its role in biological systems.
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D- and L- Configuration
The D- and L- configuration of sugars refers to the orientation of the hydroxyl group on the penultimate carbon (the second-to-last carbon) in the Fischer projection. D-sugars have the hydroxyl group on the right, while L-sugars have it on the left. This classification is essential for distinguishing between different sugar isomers and understanding their biological functions.
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Related Practice
Textbook Question
Show how the following ketones might be synthesized from the indicated acids, using any necessary reagents.
(b) methyl cyclohexyl ketone from cyclohexanecarboxylic acid
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Textbook Question
Show how you would synthesize the following compounds from the appropriate carboxylic acids or acid derivatives.
1339
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Textbook Question
Propose a mechanism for the reaction of benzoic acid with oxalyl chloride. This mechanism begins like the thionyl chloride reaction, to give a reactive mixed anhydride. Nucleophilic acyl substitution by chloride ion gives a tetrahedral intermediate that eliminates a leaving group, which then fragments into carbon dioxide, carbon monoxide, and chloride ion.
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Textbook Question
Show how to synthesize the following compounds, using appropriate carboxylic acids and amines.
(c)
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