Textbook Question
The aldaric acid of D-glucose forms two five-membered-ring lactones. Draw their structures.
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 53
A D-aldopentose is oxidized by nitric acid to an optically active aldaric acid. A Wohl degradation of the aldopentose leads to a monosaccharide that is oxidized by nitric acid to an optically inactive aldaric acid. Identify the D-aldopentose.
Verified step by step guidance1
Step 1: Understand the problem. The d-aldopentose is oxidized by nitric acid to form an optically active aldaric acid. This means the aldaric acid has chiral centers and is not a meso compound. Additionally, performing a Wohl degradation on the aldopentose reduces its carbon chain by one, resulting in a monosaccharide that, when oxidized by nitric acid, forms an optically inactive aldaric acid (a meso compound).
Step 2: Recall the oxidation of aldoses by nitric acid. Nitric acid oxidizes both the aldehyde group at C-1 and the primary alcohol group at the terminal carbon (C-5 in a pentose) to carboxylic acids, forming an aldaric acid. For the aldaric acid to be optically active, it must have chiral centers and lack a plane of symmetry.
Step 3: Analyze the Wohl degradation. The Wohl degradation removes the C-1 carbon (the aldehyde group) of the aldopentose, resulting in an aldose with one fewer carbon atom. The resulting aldose is then oxidized by nitric acid to form an aldaric acid. For this aldaric acid to be optically inactive, it must be a meso compound, meaning it has a plane of symmetry.
Step 4: Identify the d-aldopentose. The d-aldopentose must satisfy both conditions: (1) its oxidation by nitric acid produces an optically active aldaric acid, and (2) after a Wohl degradation, the resulting aldose produces an optically inactive (meso) aldaric acid upon oxidation. Based on these criteria, the d-aldopentose is D-glucose, as its structure aligns with these oxidation and symmetry properties.
Step 5: Verify the solution. Confirm that the oxidation of D-glucose by nitric acid produces an optically active aldaric acid (D-glucaric acid) and that the Wohl degradation of D-glucose produces D-arabinose, which, when oxidized by nitric acid, forms an optically inactive (meso) aldaric acid (meso-arabinaric acid). This confirms the identification of the d-aldopentose as D-glucose.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
D-Aldopentose
A D-aldopentose is a five-carbon sugar (pentose) with an aldehyde group at one end and hydroxyl groups on the other carbons. The 'D' designation indicates the configuration of the sugar, specifically that the hydroxyl group on the penultimate carbon is on the right in a Fischer projection. Common examples include ribose and arabinose, which are important in biological systems.
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Monosaccharides - D and L Isomerism
Aldaric Acid
Aldaric acid is a type of dicarboxylic acid formed from the oxidation of both the aldehyde and the primary alcohol groups of aldoses. This results in a compound with two carboxylic acid functional groups. The optical activity of aldaric acids can vary depending on the structure of the parent aldose, influencing their behavior in chemical reactions and interactions.
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Wohl Degradation
Wohl degradation is a chemical reaction that involves the conversion of aldoses into monosaccharides by cleaving the carbon chain. This process typically results in the formation of a shorter-chain sugar and can lead to changes in optical activity. The reaction is significant in carbohydrate chemistry for determining the structure and properties of sugars.
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Related Practice
Textbook Question
Draw the mechanism for the interconversion of α-D-glucose and β-D-glucose in dilute HCl.
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Textbook Question
The disaccharide lactulose consists of a D-galactopyranose subunit and a D-fructofuranose subunit joined by a β-1,4′-glycosidic linkage. After treatment of lactulose with 1. excess CH3I/Ag2O, 2. HCl/H2O, the d-galactopyranose subunit was found to have one nonmethylated OH group, whereas the D-fructofuranose subunit had two. Draw the structure of ⍺-lactulose.
Textbook Question
A hexose was obtained after (+)-glyceraldehyde underwent three successive Kiliani–Fischer syntheses. Identify the hexose from the following experimental information: oxidation with nitric acid forms an optically active aldaric acid; a Wohl degradation followed by oxidation with nitric acid forms an optically inactive aldaric acid; and a second Wohl degradation forms erythrose.
Textbook Question
Hyaluronic acid, a component of connective tissue, is the fluid that lubricates joints. It is a polymer of alternating N-acetyl-D-glucosamine and D-glucuronic acid subunits joined by β-1,3′-glycosidic linkages. Draw a short segment of hyaluronic acid.
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Textbook Question
Draw the mechanism for the formation of β-lactose from ⍺-D-galactose and β-D-glucose in dilute HCl.
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