Textbook Question
Figure 23-2 shows that the degradation of D-glucose gives D-arabinose, an aldopentose. Arabinose is most stable in its furanose form. Draw D-arabinofuranose.
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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 7
Draw the Haworth projection for the cyclic structure of D-mannose by laying down the Fischer projection.
Verified step by step guidance1
Start by identifying the Fischer projection of D-mannose. D-mannose is an aldohexose, meaning it has six carbons and an aldehyde group at the top. The hydroxyl (-OH) groups on the chiral carbons are arranged as follows: on the second carbon, the -OH is on the left; on the third carbon, the -OH is on the right; on the fourth carbon, the -OH is on the left; and on the fifth carbon, the -OH is on the right.
Determine the type of cyclic structure D-mannose forms. D-mannose typically forms a six-membered ring (pyranose) by reacting the aldehyde group on carbon 1 with the hydroxyl group on carbon 5, creating a hemiacetal linkage.
Convert the Fischer projection into a Haworth projection. To do this, orient the Fischer projection so that the groups on the right side of the Fischer projection point downward in the Haworth projection, and the groups on the left side point upward. For D-mannose, the -OH on carbon 2 points upward, the -OH on carbon 3 points downward, the -OH on carbon 4 points upward, and the -CH2OH group on carbon 5 points upward.
Add the anomeric carbon configuration. The anomeric carbon (carbon 1) can have two possible configurations: alpha (α) or beta (β). In the α-anomer, the -OH group on carbon 1 points downward, while in the β-anomer, the -OH group on carbon 1 points upward. Decide which anomer to draw based on the problem's requirements or draw both if unspecified.
Complete the Haworth projection by ensuring all atoms and bonds are correctly represented. Verify that the oxygen atom in the ring is between carbons 1 and 5, and that the substituents on each carbon are correctly positioned based on the rules for converting Fischer to Haworth projections.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Haworth Projection
The Haworth projection is a way of representing the cyclic forms of sugars, showing the arrangement of atoms in a three-dimensional perspective. It illustrates the cyclic structure of monosaccharides, where the carbon atoms are represented in a ring format, and the hydroxyl groups and other substituents are positioned above or below the plane of the ring. This representation is crucial for understanding the stereochemistry and reactivity of carbohydrates.
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Monosaccharides - Haworth Projections
Fischer Projection
The Fischer projection is a two-dimensional representation of organic molecules, particularly sugars, that displays the configuration of chiral centers. In this format, the vertical lines represent bonds going back into the plane, while horizontal lines represent bonds coming out of the plane. Converting a Fischer projection to a Haworth projection involves identifying the orientation of substituents around the chiral centers to accurately depict the cyclic structure.
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D-Mannose
D-Mannose is a naturally occurring sugar and an epimer of glucose, differing at the C2 carbon. It is an aldohexose, meaning it contains six carbon atoms and an aldehyde functional group. Understanding the specific stereochemistry of D-mannose is essential for accurately drawing its cyclic form, as the orientation of hydroxyl groups in the Fischer projection directly influences the resulting Haworth projection.
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Related Practice
Textbook Question
Which configuration (R or S) does the bottom asymmetric carbon have for the D series of sugars? Which configuration for the L series?
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Textbook Question
Talose is the C4 epimer of mannose. Draw the chair conformation of D-talopyranose.
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Textbook Question
Allose is the C3 epimer of glucose. Draw the cyclic hemiacetal form of D-allose, first in the chair conformation and then in the Haworth projection.
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Textbook Question
c. Draw d-idose, the C3 epimer of D-talose. Now compare your answers with Figure 23-3.
d. Draw the C4 “epimer” of D-xylose. Notice that this “epimer” is actually an L-series sugar, and we have seen its enantiomer. Give the correct name for this L-series sugar.
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Textbook Question
a. Draw D-allose, the C3 epimer of glucose.
b. Draw D-talose, the C2 epimer of d-galactose
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