Domanda del libro di testo
Reduction of D-fructose with a reducing agent yields a mixture of D-sorbitol along with a second, isomeric product. What is the structure of the second product?
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Ch.20 Carbohydrates
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187
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TOC.tableOfContents
- Ch.1 Matter and Measurements27
- Ch.2 Atoms and the Periodic Table20
- Ch.3 Ionic Compounds8
- Ch.4 Molecular Compounds23
- Ch.5 Classification & Balancing of Chemical Reactions12
- Ch.6 Chemical Reactions: Mole and Mass Relationships28
- Ch.7 Chemical Reactions: Energy, Rate and Equilibrium64
- Ch.8 Gases, Liquids and Solids24
- Ch.9 Solutions52
- Ch.10 Acids and Bases25
- Ch.11 Nuclear Chemistry22
- Ch.12 Introduction to Organic Chemistry: Alkanes57
- Ch.13 Alkenes, Alkynes, and Aromatic Compounds47
- Ch.14 Some Compounds with Oxygen, Sulfur, or a Halogen50
- Ch.15 Aldehydes and Ketones45
- Ch.16 Amines42
- Ch.17 Carboxylic Acids and Their Derivatives57
- Ch.18 Amino Acids and Proteins82
- Ch.19 Enzymes and Vitamins63
- Ch.20 Carbohydrates44
- Ch.21 The Generation of Biochemical Energy65
- Ch.22 Carbohydrate Metabolism45
- Ch.23 Lipids42
- Ch.24 Lipid Metabolism33
- Ch.25 Protein and Amino Acid Metabolism24
- Ch.26 Nucleic Acids and Protein Synthesis45
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187Non è quello che usi tu?Cambia libro di testo
Capitolo 20, Problema 50
In its open-chain form, D-mannose, an aldohexose found in orange peels, has the structure shown here. Coil mannose around and draw it in the cyclic hemiacetal ⍺ and β forms.
Guida verificata passo dopo passo1
Understand that d-mannose is an aldohexose, meaning it contains six carbon atoms and an aldehyde functional group. In its open-chain form, the aldehyde group is at the top (C1), and the hydroxyl groups (-OH) are attached to the other carbons in a specific stereochemical arrangement.
To form the cyclic hemiacetal, recognize that the aldehyde group at C1 reacts with the hydroxyl group on C5. This reaction creates a new ring structure, specifically a six-membered ring (pyranose form).
When the ring closes, a new chiral center is formed at C1 (the anomeric carbon). This results in two possible stereoisomers: the α-anomer (where the -OH group on the anomeric carbon is trans to the CH2OH group at C5) and the ß-anomer (where the -OH group on the anomeric carbon is cis to the CH2OH group at C5).
Draw the cyclic structure of d-mannose in its α form. Start by sketching a six-membered ring with oxygen as one of the members. Place the CH2OH group at C5 above the plane of the ring, and position the -OH group on the anomeric carbon (C1) below the plane of the ring.
Draw the cyclic structure of d-mannose in its ß form. Use the same six-membered ring structure, but this time, position the -OH group on the anomeric carbon (C1) above the plane of the ring, making it cis to the CH2OH group at C5.
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Aldohexose
Aldohexoses are a type of monosaccharide that contain six carbon atoms and an aldehyde group. D-mannose, specifically, is an aldohexose that plays a crucial role in various biological processes, including cell recognition and metabolism. Understanding its structure is essential for grasping how it interacts in biological systems.
Cyclic Hemiacetal Formation
Cyclic hemiacetals are formed when a monosaccharide reacts with itself, leading to a ring structure. In the case of d-mannose, this process involves the reaction of the aldehyde group with a hydroxyl group on the same molecule, resulting in two anomeric forms: α and ß. This transformation is vital for understanding the stability and reactivity of sugars in solution.
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Percorso guidato
2:55
Cyclic Hemiacetals Concept 2
Anomeric Forms
Anomeric forms refer to the two different configurations of a sugar molecule at the anomeric carbon, which is the carbon derived from the carbonyl group in the open-chain form. For d-mannose, the α and ß forms differ in the orientation of the hydroxyl group at this carbon. This distinction is important in biochemistry as it affects the sugar's properties and interactions with enzymes and receptors.
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Percorso guidato
02:35Periodic Table: Elemental Forms (Simplified) Concept 1
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Domanda del libro di testo
Only three stereoisomers are possible for 2,3-dibromo-2, 3-dichlorobutane. Draw them, indicating which pair are enantiomers (optical isomers). Why does the other isomer not have an enantiomer?
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Domanda del libro di testo
Treatment of D-glucose with a reducing agent yields sorbitol, a substance used as a sugar substitute by people with diabetes. Draw the structure of sorbitol.
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Domanda del libro di testo
Treatment of an aldose with an oxidizing agent such as Tollens’ reagent yields a carboxylic acid. Gluconic acid, the product of glucose oxidation, is used as its magnesium salt for the treatment of magnesium deficiency. Draw the structure of gluconic acid.
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Domanda del libro di testo
Sucrose and D-glucose rotate plane-polarized light to the right; D-fructose rotates light to the left. When sucrose is hydrolyzed, the glucose–fructose mixture rotates light to the left.
b. Why do you think the mixture is called “invert sugar”?
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Domanda del libro di testo
In Section 15.6, you saw that aldehydes react with reducing agents to yield primary alcohols (RCH=O → RCH2OH). The structures of two D-aldotetroses are shown. One of them can be reduced to yield a chiral product, but the other yields an achiral product. Explain.
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