Textbook Question
Answer the following questions about the eight aldopentoses:
a. Which are enantiomers?
b. Which are C-2 epimers?
Ch. 20 - The Organic Chemistry of Carbohydrates
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
Chapter 21, Problem 36b
Identify the sugar in each description.
b. A sugar that is not D-altrose forms D-altraric acid when it is oxidized with nitric acid.
Verified step by step guidance1
Step 1: Understand the problem. The question asks us to identify a sugar that, when oxidized with nitric acid, forms D-altraric acid. This involves understanding the oxidation process and the structure of D-altraric acid.
Step 2: Recall the oxidation reaction with nitric acid. When a sugar is treated with nitric acid, both the aldehyde group (or ketone group) and the primary alcohol group are oxidized to carboxylic acids. This reaction converts aldoses or ketoses into dicarboxylic acids.
Step 3: Analyze the structure of D-altraric acid. D-altraric acid is a meso compound derived from D-altrose. It has two carboxylic acid groups at the ends of the molecule and specific stereochemistry at its chiral centers. This stereochemistry is key to identifying the sugar precursor.
Step 4: Determine the sugar precursor. Since the sugar is not D-altrose but forms D-altraric acid upon oxidation, it must be a diastereomer of D-altrose. Diastereomers have the same molecular formula but differ in the configuration of one or more chiral centers.
Step 5: Compare the stereochemistry of D-altrose with its diastereomers. Identify the diastereomer that, upon oxidation, would yield the same stereochemical arrangement as D-altraric acid. This sugar is the answer to the problem.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
D-Altraric Acid Formation
D-Altraric acid is a dicarboxylic acid formed from the oxidation of certain sugars. When sugars are oxidized, their aldehyde or alcohol groups can be converted into carboxylic acids. In this case, the oxidation of a sugar that is not d-altrose leads to the formation of D-altraric acid, indicating specific structural features of the sugar involved.
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Oxidation Reactions in Sugars
Oxidation reactions in organic chemistry involve the loss of electrons or an increase in oxidation state. For sugars, this often means converting hydroxyl groups into carbonyl groups or carboxylic acids. Understanding how different sugars react to oxidizing agents, like nitric acid, is crucial for identifying their structures and derivatives.
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Sugar Classification
Sugars can be classified based on their structure and functional groups, such as aldoses and ketoses. D-altrose is an aldose, which contains an aldehyde group. Recognizing the differences between various sugars, including their stereochemistry and functional groups, is essential for determining which sugar is being described in the context of oxidation reactions.
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Related Practice
Textbook Question
Name the epimers of D-glucose.
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Textbook Question
Identify the sugar in each description.
c. A ketose that, when reduced with NaBH4, forms D-altritol and D-allitol.
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Textbook Question
Identify the sugar in each description.
a. An aldopentose that is not D-arabinose forms D-arabinitol when it is reduced with NaBH4.
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Textbook Question
What product or products are obtained when d-galactose reacts with each of the following?
g.
1. hydroxylamine/trace acid
2. acetic anhydride/∆
3. HO-/H2O
Textbook Question
D-Xylose and D-lyxose are formed when d-threose undergoes a Kiliani–Fischer synthesis. D-Xylose is oxidized to an optically inactive aldaric acid, whereas D-lyxose forms an optically active aldaric acid. What are the structures of D-xylose and D-lyxose?
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