Textbook Question
Predict the products obtained when D-galactose reacts with each reagent.
(e) H2, Ni
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Ch. 23 - Carbohydrates and Nucleic Acids
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 23, Problem 52b
Predict the products obtained when d-galactose reacts with each reagent.
(b) NaOH, H2O
Verified step by step guidance1
Identify the structure of D-galactose: D-galactose is an aldohexose, meaning it contains six carbon atoms and an aldehyde functional group at the first carbon. It also has hydroxyl (-OH) groups attached to the other carbons in a specific stereochemical arrangement.
Understand the reaction conditions: The reagents NaOH and H2O indicate a basic aqueous environment. In such conditions, aldoses like D-galactose can undergo enediol rearrangement, which involves the formation of an enediol intermediate.
Describe the enediol rearrangement: The aldehyde group at C1 of D-galactose reacts with the hydroxide ion (OH⁻) to form an enolate ion. This enolate ion tautomerizes to form an enediol intermediate, which has hydroxyl groups on both C1 and C2.
Explain the possible outcomes: The enediol intermediate can rearrange back to the original aldehyde form (D-galactose) or isomerize to form other sugars. Specifically, D-galactose can isomerize to D-mannose or D-glucose, as these are epimers of D-galactose at different carbon centers (C2 and C4, respectively).
Summarize the products: The reaction in basic aqueous conditions will yield a mixture of D-galactose, D-glucose, and D-mannose due to the enediol rearrangement and isomerization processes.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
D-Galactose Structure
D-galactose is a six-carbon aldose sugar with a specific stereochemistry. It contains an aldehyde functional group and multiple hydroxyl groups, which influence its reactivity. Understanding its structure is crucial for predicting how it will interact with reagents like NaOH.
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06:47
Monosaccharides - D and L Isomerism
Aldose Reactivity
Aldoses, such as d-galactose, can undergo various reactions, including oxidation, reduction, and glycosidic bond formation. In the presence of a strong base like NaOH, aldoses can undergo isomerization or aldol reactions, which are essential to consider when predicting reaction products.
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01:17Reactivity of Molecules
Base-Catalyzed Reactions
In organic chemistry, strong bases like NaOH can facilitate reactions by deprotonating functional groups or promoting nucleophilic attacks. In the case of d-galactose, NaOH can lead to the formation of an enolate ion, which can then react with water or other substrates, affecting the final products of the reaction.
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01:57Base Catalyzed
Related Practice
Textbook Question
Predict the products obtained when D-galactose reacts with each reagent.
(d) Ag(NH3)2+ –OH
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Textbook Question
Classify the following monosaccharides. (Examples: D-aldohexose, L-ketotetrose.)
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Textbook Question
(a) Give the products expected when (+)-glyceraldehyde reacts with HCN.
(b) What is the relationship between the products? How might they be separated?
(c) Are the products optically active? Explain.
Textbook Question
The relative configurations of the stereoisomers of tartaric acid were established by the following syntheses:
(1) D-(+)-glyceraldehyde diastereomers A and B (separated)
(2) Hydrolysis of A and B using aqueous Ba(OH)2 gave C and D, respectively.
(3) HNO3 oxidation of C and D gave (-)-tartaric acid and meso-tartaric acid, respectively.
(a) You know the absolute configuration of D-(+)-glyceraldehyde. Use Fischer projections to show the absolute configurations of products A, B, C, and D.
(b) Show the absolute configurations of the three stereoisomers of tartaric acid: (+)-tartaric acid, (-)-tartaric acid, and meso-tartaric acid.
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Textbook Question
Predict the products obtained when d-galactose reacts with each reagent.
(c) CH3OH, H+
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