Textbook Question
Ketohexoses form from aldohexoses. Suggest a mechanism for the acid-catalyzed version of this reaction. What type of reaction is this? [You’ve seen it before.]
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Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
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Table of contents
- Ch. 2 - General Chemistry Translated: Finding the Electrons114
- Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis109
- Ch. 4 - Acids and Bases: Electron Flow144
- Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics118
- Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space112
- Ch. 7 - Principles of Green (Organic) Chemistry3
- Ch. 8 - Alkenes I: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes II: Oxidation and Reduction150
- Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions101
- Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions108
- Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes172
- Ch. 13 - Alcohols, Ethers and Related Compounds: Substitution and Elimination239
- Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution I: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution II: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems I: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems II: Pericyclic Reactions54
- Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring62
- Ch. 25 - Amines: Structure, Reactions, and Synthesis27
- Ch. 26 - Amino Acids, Proteins, and Peptide Synthesis9
- Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids54
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
Chapter 26, Problem 39a
In each of the disaccharides shown (a–c), (i) identify the reducing end of the sugar, (ii) tell what monosaccharides are used to make it, and (iii) tell what type of glycoside linkage is present.
(a) 
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Identify the reducing end of the sugar: Look for the anomeric carbon that is not involved in a glycosidic bond. In the given disaccharide, the rightmost sugar has a free anomeric carbon (the carbon attached to the OH group that is not involved in the glycosidic bond), indicating the reducing end.
Determine the monosaccharides: Examine the structure of each sugar unit. The left sugar unit is a glucose molecule, as indicated by the presence of an aldohexose structure with hydroxyl groups in the correct orientation. The right sugar unit is also a glucose molecule.
Identify the type of glycosidic linkage: Look at the oxygen bridge connecting the two sugar units. The linkage is between the anomeric carbon of the left glucose and the fourth carbon of the right glucose, indicating a 1→4 linkage. Since the anomeric carbon of the left glucose is in the beta configuration (the OH group is equatorial), the linkage is a β(1→4) glycosidic bond.
Verify the orientation of the glycosidic bond: Ensure that the glycosidic bond is consistent with the beta configuration by checking the orientation of the OH group on the anomeric carbon. In this case, the OH group is equatorial, confirming the beta linkage.
Summarize the findings: The disaccharide consists of two glucose units linked by a β(1→4) glycosidic bond, with the reducing end being the rightmost glucose unit.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Reducing Sugars
Reducing sugars are carbohydrates that can donate electrons to other molecules, typically due to the presence of a free aldehyde or ketone group. In disaccharides, the reducing end is the monosaccharide unit that retains this reactive group, allowing it to participate in redox reactions. Identifying the reducing end is crucial for understanding the reactivity and properties of the sugar.
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Reducing Sugars
Monosaccharide Composition
Disaccharides are formed by the condensation of two monosaccharides, which are the simplest form of carbohydrates. Understanding the specific monosaccharides involved in the formation of a disaccharide is essential for determining its structure and properties. Common examples include glucose, fructose, and galactose, which can combine in various ways to form different disaccharides.
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12:01Monosaccharide
Glycosidic Linkage
A glycosidic linkage is a covalent bond that connects two monosaccharides through a dehydration reaction, resulting in the formation of a disaccharide. The type of glycosidic linkage is defined by the specific carbon atoms involved in the bond and their orientation (alpha or beta). This linkage significantly influences the disaccharide's stability, digestibility, and biological function.
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Related Practice
Textbook Question
Maltose, like cellobiose, is composed of two glucose units. What is the difference between maltose and cellobiose?
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Textbook Question
Identify the product when each of the following reactions is performed on the triglyceride of linoleic acid (linoleate).
(a) H2 , Pd
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Textbook Question
Predict the product of each of the following reactions.
(d)
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Textbook Question
In each of the disaccharides shown (a–c), (i) identify the reducing end of the sugar, (ii) tell what monosaccharides are used to make it, and (iii) tell what type of glycoside linkage is present.
(b)
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Textbook Question
Predict the product of each of the following reactions.
(c)
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