Textbook Question
Name the epimers of D-glucose.
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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 36a
Identify the sugar in each description.
a. An aldopentose that is not D-arabinose forms D-arabinitol when it is reduced with NaBH4.
Verified step by step guidance1
Step 1: Understand the problem. The question asks us to identify an aldopentose (a five-carbon sugar with an aldehyde group) that is not D-arabinose but forms D-arabinitol upon reduction with sodium borohydride (NaBH4). Reduction of an aldose with NaBH4 converts the aldehyde group (-CHO) into a primary alcohol (-CH2OH), resulting in a sugar alcohol (alditol).
Step 2: Recall the structure of D-arabinose. D-arabinose is an aldopentose with a specific stereochemistry at its chiral centers. When reduced, it forms D-arabinitol, a sugar alcohol with the same stereochemistry as D-arabinose.
Step 3: Consider other aldopentoses. The aldopentoses include D-ribose, D-xylose, D-lyxose, and D-arabinose. Since the problem specifies that the sugar is not D-arabinose, we need to determine which of the remaining aldopentoses also forms D-arabinitol upon reduction.
Step 4: Analyze stereochemistry. Reduction of an aldopentose preserves the stereochemistry of its chiral centers. Therefore, the aldopentose that forms D-arabinitol upon reduction must have the same stereochemical configuration as D-arabinose at all chiral centers except the carbonyl carbon (C1).
Step 5: Identify the sugar. Compare the stereochemistry of the remaining aldopentoses (D-ribose, D-xylose, and D-lyxose) to that of D-arabinose. The aldopentose with the same stereochemistry as D-arabinose at C2, C3, and C4 is the correct answer. This sugar will form D-arabinitol upon reduction with NaBH4.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Aldopentose
An aldopentose is a type of monosaccharide that contains five carbon atoms and an aldehyde functional group. The general formula for aldopentoses is C5H10O5. Understanding the structure and properties of aldopentoses is crucial for identifying specific sugars based on their chemical reactions and transformations.
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Reduction with NaBH4
Sodium borohydride (NaBH4) is a common reducing agent used in organic chemistry to convert carbonyl groups (aldehydes and ketones) into alcohols. When an aldopentose is reduced with NaBH4, the aldehyde group is transformed into a primary alcohol, leading to the formation of sugar alcohols, such as d-arabinitol in this case.
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Sugar Alcohols
Sugar alcohols, or polyols, are organic compounds derived from sugars by reducing the carbonyl group to an alcohol group. They are often used as sweeteners and have different physical properties compared to their parent sugars. Recognizing the relationship between sugars and their corresponding sugar alcohols is essential for understanding biochemical pathways and reactions in organic chemistry.
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Related Practice
Textbook Question
What product or products are obtained when D-galactose reacts with each of the following?
f. ethanol + HCl
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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
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
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.
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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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