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Ch.13 Carbohydrates
Timberlake - Chemistry: An Introduction to General, Organic, and Biological Chemistry 14th Edition
Timberlake14th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9781292472249Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoTimberlake 14th EditionCh.13 CarbohydratesProblema 57c
Capitolo 13, Problema 57c

Melezitose, a carbohydrate secreted by insects, has the following Haworth structure:
Haworth structure of melezitose, a carbohydrate secreted by insects, with labeled hydroxyl groups and molecular formula.
c. Is melezitose a reducing sugar?

Guida verificata passo dopo passo
1
Step 1: Understand the concept of a reducing sugar. A reducing sugar is a carbohydrate that can act as a reducing agent because it has a free aldehyde group (-CHO) or a free ketone group (-C=O) in its open-chain form. This property allows it to reduce other compounds, such as Benedict's reagent.
Step 2: Analyze the structure of raffinose. Raffinose is a trisaccharide composed of galactose, glucose, and fructose. In its structure, the glucose unit is linked to the galactose and fructose units through glycosidic bonds.
Step 3: Determine if the glucose unit in raffinose has a free anomeric carbon. The anomeric carbon is the carbon derived from the carbonyl group (C=O) in the open-chain form of the sugar. If this carbon is involved in a glycosidic bond, it is not free and cannot participate in redox reactions.
Step 4: Evaluate the fructose unit in raffinose. Fructose is a ketose sugar, and its anomeric carbon can also be involved in glycosidic bonding. If both the glucose and fructose units have their anomeric carbons involved in glycosidic bonds, raffinose will not have a free reducing end.
Step 5: Conclude whether raffinose is a reducing sugar. Based on the analysis, if all anomeric carbons in raffinose are involved in glycosidic bonds, it cannot act as a reducing sugar. This means raffinose is a non-reducing sugar.

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Reducing Sugars

Reducing sugars are carbohydrates that can donate electrons to another chemical, typically due to the presence of a free aldehyde or ketone group. This property allows them to reduce other compounds, which is a key characteristic in various biochemical reactions. Common examples include glucose and fructose, which can participate in redox reactions.
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1:03
Ketoses as Reducing Sugars Concept 2

Raffinose Structure

Raffinose is a trisaccharide composed of galactose, glucose, and fructose. Its structure includes a galactose unit linked to a sucrose molecule, which is a combination of glucose and fructose. Understanding its structure is essential to determine its reactivity and whether it can act as a reducing sugar.
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1:01
Structural Formula Concept 2

Haworth Projection

The Haworth projection is a way of representing the cyclic structure of carbohydrates, showing the arrangement of atoms in a ring form. This representation helps visualize the orientation of hydroxyl groups and other substituents, which is crucial for understanding the chemical properties and reactivity of sugars, including whether they are reducing or non-reducing.
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Intro to Haworth Projections Concept 1
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