Textbook Question
Without referring to the chapter, draw the chair conformations of
(d) N-acetylglucosamine, glucose with the C2 oxygen atom replaced by an acetylated amino group.
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Ch. 23 - Carbohydrates and Nucleic 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 23, Problem 47c
Without referring to the chapter, draw the chair conformations of
(c) β-D-galactopyranose (the C4 epimer of glucose).
Verified step by step guidance1
Understand the structure of β-D-galactopyranose: It is a six-membered cyclic sugar (pyranose form) with the hydroxyl group at the anomeric carbon (C1) in the beta configuration (equatorial position). Galactose is the C4 epimer of glucose, meaning the configuration of the hydroxyl group at C4 is different from that of glucose.
Draw the basic chair conformation of a six-membered ring: Start by sketching a cyclohexane chair structure. Label the carbon atoms from C1 to C6 in a clockwise direction, with C1 at the top right corner.
Place the substituents on the ring: Add the hydroxyl groups and hydrogen atoms to each carbon based on the stereochemistry of β-D-galactopyranose. For β-D-galactopyranose: (1) At C1, place the hydroxyl group in the equatorial position and the hydrogen in the axial position. (2) At C2, place the hydroxyl group in the equatorial position. (3) At C3, place the hydroxyl group in the axial position. (4) At C4, place the hydroxyl group in the axial position (this is the key difference from glucose). (5) At C5, place the hydroxyl group in the equatorial position. (6) At C6, place the CH2OH group in the equatorial position.
Verify the stereochemistry: Double-check that the substituents match the stereochemistry of β-D-galactopyranose, ensuring that the hydroxyl group at C4 is in the axial position, distinguishing it from glucose.
Finalize the drawing: Clearly label the chair conformation with all substituents, ensuring the beta configuration at C1 and the correct stereochemistry at all other carbons. This will give you the chair conformation of β-D-galactopyranose.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Chair Conformation
The chair conformation is a three-dimensional representation of cyclohexane and its derivatives, which minimizes steric strain and torsional strain. In this conformation, the carbon atoms are arranged in a way that allows for staggered bonds, making it the most stable form of cyclohexane. Understanding chair conformations is crucial for visualizing the spatial arrangement of substituents on cyclic structures, such as sugars.
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Understanding what a conformer is.
Anomeric Carbon
The anomeric carbon is the carbon atom in a sugar that is derived from the carbonyl carbon during the formation of a cyclic structure. In pyranoses, this carbon is typically the first carbon (C1) and is crucial for determining the alpha or beta configuration of the sugar. The orientation of the hydroxyl group on the anomeric carbon relative to the CH2OH group defines whether the sugar is in the alpha or beta form, which is essential for understanding the properties of carbohydrates.
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Epimers
Epimers are a specific type of diastereomer that differ in configuration at only one stereogenic center. In the case of b-D-galactopyranose and glucose, they differ at the C4 position, making them C4 epimers. Recognizing epimers is important in carbohydrate chemistry as it influences the physical and chemical properties of sugars, including their reactivity and biological roles.
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Related Practice
Textbook Question
Use Figure 23-3 (the D family of aldoses) to name the following aldoses.
(a) the C2 epimer of D-arabinose
(b) the C3 epimer of D-mannose
(c) the C3 epimer of D-threose
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Textbook Question
Without referring to the chapter, draw the chair conformations of
(b) α-D-allopyranose (the C3 epimer of glucose).
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Textbook Question
Glucose is the most abundant monosaccharide. From memory, draw glucose in
(a) the Fischer projection of the open chain.
(b) the most stable chair conformation of the most stable pyranose anomer.
(c) the Haworth projection of the most stable pyranose anomer.
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Textbook Question
Classify the following monosaccharides. (Examples: D-aldohexose, L-ketotetrose.)
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Textbook Question
Without referring to the chapter, draw the chair conformations of
(a) β-D-mannopyranose (the C2 epimer of glucose).
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