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Ch. 20 - The Organic Chemistry of Carbohydrates
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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TOC.tableOfContents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding31
- 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
Capitolo 20, Problema 43
Propose a mechanism for the formation of d-allose from d-glucose in a basic solution.
Guida verificata passo dopo passo1
Identify the structural difference between D-glucose and D-allose. D-glucose is an aldohexose with the hydroxyl group on carbon 3 (C3) pointing to the left in a Fischer projection, while in D-allose, the hydroxyl group on C3 points to the right. This indicates that the reaction involves an epimerization at C3.
Understand the role of the basic solution. In a basic environment, the alpha-hydrogen on the carbon adjacent to the carbonyl group (C2 in this case) is slightly acidic and can be deprotonated by the base, forming an enolate ion.
Propose the first step of the mechanism: Deprotonation. The base abstracts the alpha-hydrogen from C2 of D-glucose, forming an enolate intermediate. Represent this step using the enolate structure: .
Propose the second step of the mechanism: Reprotonation. The enolate intermediate can be reprotonated at the C3 position from either side, leading to the formation of two possible epimers: D-glucose (if the hydroxyl group is re-added to the left) or D-allose (if the hydroxyl group is re-added to the right).
Conclude the mechanism: The equilibrium between the enolate intermediate and the two epimers allows for the interconversion of D-glucose and D-allose. In the presence of a base, this process is reversible, and the reaction mixture will contain both epimers.
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Epimerization
Epimerization is a specific type of stereoisomerism where two sugars differ in configuration at only one specific carbon atom. In the case of d-allose and d-glucose, they are epimers at the C-2 position. Understanding this concept is crucial for proposing a mechanism that involves the conversion of one sugar to another through the alteration of stereochemistry.
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02:57
General Reaction
Basic Conditions
Basic conditions refer to an environment where the pH is greater than 7, often involving hydroxide ions (OH-). In organic reactions, basic conditions can facilitate deprotonation and nucleophilic attacks, which are essential for rearranging molecular structures. Recognizing how these conditions influence reaction pathways is vital for understanding the mechanism of d-allose formation from d-glucose.
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06:21Understanding the difference between basicity and nucleophilicity.
Nucleophilic Attack
Nucleophilic attack is a fundamental reaction mechanism in organic chemistry where a nucleophile donates an electron pair to an electrophile, forming a chemical bond. In the context of sugar interconversion, nucleophilic attack can lead to the opening of the sugar's ring structure, allowing for the rearrangement of functional groups. This concept is key to understanding how d-glucose can be transformed into d-allose through a series of reaction steps.
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08:27Nucleophilic Addition
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