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 34f
What product or products are obtained when D-galactose reacts with each of the following?
f. ethanol + HCl
Verified step by step guidance1
Identify the functional groups present in d-galactose. D-galactose is an aldose sugar with an aldehyde group (-CHO) at the anomeric carbon and multiple hydroxyl (-OH) groups.
Understand the reaction conditions. Ethanol (C₂H₅OH) in the presence of HCl acts as an acid catalyst, promoting the formation of acetal or hemiacetal derivatives at the anomeric carbon of d-galactose.
Focus on the anomeric carbon. The aldehyde group at the anomeric carbon reacts with ethanol to form a glycosidic bond, resulting in the formation of an ethyl glycoside. This reaction produces two stereoisomers: α- and β-ethyl galactosides, depending on the orientation of the substituent at the anomeric carbon.
Write the general reaction mechanism. The aldehyde group first reacts with ethanol to form a hemiacetal intermediate. In the presence of HCl, the hemiacetal is further converted into a full acetal (glycoside) by replacing the hydroxyl group with an ethoxy group (-OCH₂CH₃).
Conclude the products. The reaction yields a mixture of α-ethyl galactoside and β-ethyl galactoside as the final products, due to the equilibrium between the two stereoisomers.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Monosaccharide Structure
D-galactose is a monosaccharide, specifically an aldohexose, which means it contains six carbon atoms and an aldehyde functional group. Understanding its structure is crucial for predicting how it will react with other compounds, as the configuration of hydroxyl groups can influence reactivity and product formation.
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Monosaccharides - Common Structures
Esterification Reaction
The reaction of d-galactose with ethanol in the presence of HCl typically leads to esterification, where the hydroxyl group of the sugar reacts with the alcohol to form an ester. This process involves the formation of a glycosidic bond, which is essential for understanding how sugars can be modified chemically.
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Acid-Catalyzed Reactions
HCl acts as a catalyst in this reaction, facilitating the conversion of d-galactose and ethanol into products. Acid-catalyzed reactions often enhance the reactivity of alcohols and sugars, making it important to recognize how acids can influence the mechanism and outcome of organic reactions.
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Related Practice
Textbook Question
What product or products are obtained when D-galactose reacts with each of the following?
e. Br2 in water
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Textbook Question
Identify the sugar in each description.
a. An aldopentose that is not D-arabinose forms D-arabinitol when it is reduced with NaBH4.
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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
What product or products are obtained when d-galactose reacts with each of the following?
d. excess CH3I + Ag2O
Textbook Question
What product or products are obtained when D-galactose reacts with each of the following?
c. NaBH4, followed by H3O+
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