Domanda del libro di testo
Starting with a Fischer projection of d-glucose (and other sugars), switch only the stereocenter that gave it the designation of d. What new sugar have you made? [Hint: The answer is not l-glucose.]
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Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
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TOC.tableOfContents
- 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 1: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes 2: 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 1: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification 2: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution 1: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution 2: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems 1: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems 2: Pericyclic Reactions54
- Ch. 23 - Benzene 1: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene 2: 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: 9780137566471Non è quello che usi tu?Cambia libro di testo
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Mullins 1st EditionCh. 27 - Carbohydrates, Nucleic Acids, and LipidsProblema 68
Mullins 1st EditionCh. 27 - Carbohydrates, Nucleic Acids, and LipidsProblema 68Capitolo 26, Problema 68
The α- and β-anomers of glucose are shown here. In solution, these two epimers can interconvert through a process called mutarotation.
Given that α-D-glucose has a specific rotation of + 112.2° , why is the specific rotation of β-D-glucose not -112.2°? What molecule would have a specific rotation of -112.2°?
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Understand the concept of mutarotation: Mutarotation is the process by which the α- and β-anomers of a sugar interconvert in aqueous solution through the open-chain form of the sugar. This results in a change in the specific rotation of the solution until equilibrium is reached.
Recognize that the specific rotation of a compound is an intrinsic property that depends on its molecular structure. The specific rotation of α-d-glucose is +112.2°, but the specific rotation of β-d-glucose is not simply the negative of this value because the two anomers are not mirror images of each other (they are epimers, differing only at the anomeric carbon).
Recall that a molecule with a specific rotation of -112.2° would need to be the enantiomer of α-d-glucose. Enantiomers are non-superimposable mirror images of each other, and they have specific rotations that are equal in magnitude but opposite in sign.
Identify the enantiomer of α-d-glucose: The enantiomer of α-d-glucose is α-l-glucose. This molecule would have a specific rotation of -112.2° because it is the mirror image of α-d-glucose.
Conclude that β-d-glucose is not the enantiomer of α-d-glucose, but rather an epimer. Therefore, its specific rotation is not simply the negative of +112.2°. Instead, β-d-glucose has its own specific rotation value, which is determined experimentally.
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Anomers
Anomers are a type of stereoisomer found in carbohydrates, specifically cyclic forms of sugars. They differ at the anomeric carbon, which is the carbon atom that becomes a new chiral center when a sugar cyclizes. In the case of glucose, the α- and β-anomers differ in the orientation of the hydroxyl group (-OH) at the anomeric carbon, leading to distinct physical properties, including specific rotation.
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Monosaccharides - Cyclization
Specific Rotation
Specific rotation is a measure of how much a chiral compound can rotate plane-polarized light, expressed in degrees. It is influenced by the molecular structure and the concentration of the solution. Each anomer of glucose has a unique specific rotation due to differences in their spatial arrangement, which affects how they interact with light. The specific rotation is not simply the negative of the other anomer's value because it depends on the overall molecular configuration.
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05:43Specific rotation vs. observed rotation.
Mutarotation
Mutarotation is the process by which anomeric forms of a sugar interconvert in solution, leading to a change in optical rotation over time. This occurs as the sugar equilibrates between its α and β forms, which can be influenced by factors such as temperature and concentration. The specific rotation of a mixture of anomers will stabilize at a value that reflects the proportions of each form present, rather than being a simple average of their individual rotations.
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03:06Mechanism
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