Textbook Question
Classify the four carbohydrates (a)–(d) by indicating the nature of the carbonyl group and the number of carbon atoms present. For example, glucose is an aldohexose.
c.
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Ch.20 Carbohydrates
McMurry8th EditionFundamentals of GOBISBN: 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
Chapter 20, Problem 35
Draw the open-chain structure of a 4-carbon deoxy sugar.
Verified step by step guidance1
Understand the term 'deoxy sugar': A deoxy sugar is a sugar molecule in which one hydroxyl group (-OH) is replaced by a hydrogen atom (-H). This means the sugar will have one less oxygen atom than a typical sugar of the same carbon count.
Identify the structure of a 4-carbon sugar: A 4-carbon sugar is called a tetrose. The general formula for a tetrose is C₄H₈O₄, but for a deoxy sugar, one oxygen is removed, making the formula C₄H₈O₃.
Draw the backbone of the sugar: Start with a straight chain of four carbon atoms. Label them as C1, C2, C3, and C4 from top to bottom.
Add functional groups: Attach a double-bonded oxygen (C=O) to the first carbon (C1) to represent the aldehyde group (if it is an aldose) or place the carbonyl group on the second carbon (if it is a ketose). Attach hydroxyl groups (-OH) to the remaining carbons, except for the one where the deoxygenation occurs (replace one -OH with -H).
Ensure proper hydrogen placement: Add hydrogen atoms to the remaining bonds of each carbon to satisfy the valency of carbon (4 bonds per carbon atom). Double-check that the structure has the correct number of hydrogens and oxygens to match the formula C₄H₈O₃.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Deoxy Sugars
Deoxy sugars are carbohydrates that have one less oxygen atom than their corresponding sugars. In the case of a deoxy sugar, the hydroxyl group (-OH) on the second carbon is replaced by a hydrogen atom, resulting in a structure that is less oxidized. This modification is significant in biological systems, as it alters the sugar's properties and its role in nucleic acids.
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Ketoses as Reducing Sugars Example 2
Open-Chain Structure
The open-chain structure of sugars refers to their linear form, as opposed to their cyclic forms. In this structure, the carbon atoms are connected in a straight chain, with functional groups such as hydroxyls attached. For a 4-carbon deoxy sugar, the open-chain structure will include four carbon atoms, with the appropriate number of hydrogen and hydroxyl groups, illustrating the sugar's basic framework.
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Carbon Atoms in Sugars
Sugars are classified based on the number of carbon atoms they contain. A 4-carbon sugar, also known as a tetrose, has four carbon atoms in its backbone. Each carbon can be bonded to hydrogen atoms and functional groups, which determine the sugar's specific characteristics and reactivity. Understanding the arrangement of these carbon atoms is crucial for drawing the correct open-chain structure.
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Related Practice
Textbook Question
Classify the four carbohydrates (a)–(d) by indicating the nature of the carbonyl group and the number of carbon atoms present. For example, glucose is an aldohexose.
d.
931
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Textbook Question
How many chiral carbon atoms are present in each of the molecules shown in Problem 20.31?
a.
b.
c.
d.
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Textbook Question
Name four important monosaccharides and tell where each occurs in nature.
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Textbook Question
Only three stereoisomers are possible for 2,3-dibromo-2, 3-dichlorobutane. Draw them, indicating which pair are enantiomers (optical isomers). Why does the other isomer not have an enantiomer?
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Textbook Question
In Section 15.6, you saw that aldehydes react with reducing agents to yield primary alcohols (RCH=O → RCH2OH). The structures of two D-aldotetroses are shown. One of them can be reduced to yield a chiral product, but the other yields an achiral product. Explain.
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