Textbook Question
Draw the structure that completes the mutarotation reaction between the two cyclic forms of (a) galactose and (b) fructose.
b.
Ch.20 Carbohydrates
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187
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Table of contents
- Ch.1 Matter and Measurements27
- Ch.2 Atoms and the Periodic Table20
- Ch.3 Ionic Compounds8
- Ch.4 Molecular Compounds23
- Ch.5 Classification & Balancing of Chemical Reactions12
- Ch.6 Chemical Reactions: Mole and Mass Relationships28
- Ch.7 Chemical Reactions: Energy, Rate and Equilibrium64
- Ch.8 Gases, Liquids and Solids24
- Ch.9 Solutions52
- Ch.10 Acids and Bases25
- Ch.11 Nuclear Chemistry22
- Ch.12 Introduction to Organic Chemistry: Alkanes57
- Ch.13 Alkenes, Alkynes, and Aromatic Compounds47
- Ch.14 Some Compounds with Oxygen, Sulfur, or a Halogen50
- Ch.15 Aldehydes and Ketones45
- Ch.16 Amines42
- Ch.17 Carboxylic Acids and Their Derivatives57
- Ch.18 Amino Acids and Proteins82
- Ch.19 Enzymes and Vitamins63
- Ch.20 Carbohydrates44
- Ch.21 The Generation of Biochemical Energy65
- Ch.22 Carbohydrate Metabolism45
- Ch.23 Lipids42
- Ch.24 Lipid Metabolism33
- Ch.25 Protein and Amino Acid Metabolism24
- Ch.26 Nucleic Acids and Protein Synthesis45
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187Not the one you use?Change textbook
Chapter 20, Problem 7
D-Talose, a constituent of certain antibiotics, has the open-chain structure shown next. Draw d-talose in its cyclic hemiacetal form.
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Identify the functional groups in the open-chain structure of d-talose. Specifically, note the aldehyde group at the top and the hydroxyl (-OH) groups attached to the carbon chain.
Recall that the cyclic hemiacetal form of a sugar is formed when the hydroxyl group on the penultimate carbon (the second-to-last carbon) reacts with the aldehyde group to form a ring structure.
Determine the size of the ring. For d-talose, the reaction typically forms a six-membered ring (a pyranose form) because the hydroxyl group on carbon-5 reacts with the aldehyde group on carbon-1.
Draw the six-membered ring structure. Place oxygen as one of the ring atoms, and arrange the remaining carbon atoms around the ring. Ensure that the substituents (hydroxyl groups and hydrogens) are positioned correctly based on the stereochemistry of d-talose.
Add the anomeric hydroxyl group at carbon-1. This hydroxyl group can be either in the alpha (down) or beta (up) position, depending on the specific anomer of d-talose being drawn.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Hemiacetal Formation
A hemiacetal is formed when an alcohol reacts with an aldehyde or ketone. In the case of d-talose, the aldehyde group at one end of the sugar reacts with a hydroxyl group on the same molecule, resulting in a cyclic structure. This reaction is crucial for understanding how monosaccharides like d-talose can exist in both open-chain and cyclic forms.
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Cyclic Sugar Structures
Monosaccharides can exist in cyclic forms due to the intramolecular reaction between their carbonyl group and a hydroxyl group. For d-talose, this results in a six-membered ring structure known as a pyranose. Understanding the cyclic structure is essential for grasping the stability and reactivity of sugars in biological systems.
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Anomeric Carbon
The anomeric carbon is the carbon atom in a sugar that was part of the carbonyl group in its open-chain form and becomes a new chiral center in the cyclic form. In d-talose, the anomeric carbon determines the configuration of the sugar (alpha or beta) and plays a significant role in its chemical properties and interactions with other molecules.
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Related Practice
Textbook Question
Draw the enantiomer of the following monosaccharides, and in each pair identify the D sugar and the L sugar.
a.
Textbook Question
Draw the enantiomer of the following monosaccharides, and in each pair identify the D sugar and the L sugar.
b.
Textbook Question
Draw the structure that completes the mutarotation reaction between the two cyclic forms of (a) galactose and (b) fructose.
a.
Textbook Question
Aldoheptoses have five chiral carbon atoms. What is the maximum possible number of aldoheptose stereoisomers? Draw all of the aldoheptose stereoisomers.
Textbook Question
The cyclic structure of D-idose, an aldohexose, is shown in the margin. Convert this to the straight-chain Fischer projection structure.