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Ch.20 Carbohydrates
McMurry - Fundamentals of General, Organic, and Biological Chemistry 8th Edition
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187Not the one you use?Change textbook
All textbooksMcMurry 8th EditionCh.20 CarbohydratesProblem 23c
Chapter 20, Problem 23c

Hydrolysis of both glycosidic bonds in the following trisaccharide A, B, C yields three monosaccharides. 
c. Draw the Fischer projections for the three monosaccharides.

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1
Identify the structure of the given trisaccharide and locate the glycosidic bonds. Glycosidic bonds are the covalent bonds that link monosaccharides together in a polysaccharide or oligosaccharide.
Understand that hydrolysis involves breaking the glycosidic bonds by adding water molecules. Each glycosidic bond will break, resulting in the release of individual monosaccharides.
Determine the monosaccharides that are released upon hydrolysis. Analyze the structure of the trisaccharide to identify the three monosaccharides (A, B, and C) that are formed.
Recall the Fischer projection, which is a two-dimensional representation of a molecule showing the configuration of chiral centers. For each monosaccharide, draw its Fischer projection by arranging the carbon chain vertically, with the most oxidized carbon (the carbonyl group) at the top.
Ensure that the stereochemistry of each chiral center in the monosaccharides is correctly represented in the Fischer projections. Verify the orientation of hydroxyl (-OH) groups on each carbon atom to match the original structure of the monosaccharides.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Glycosidic Bonds

Glycosidic bonds are covalent linkages formed between monosaccharides through a dehydration reaction, resulting in the formation of disaccharides or polysaccharides. In the context of trisaccharides, hydrolysis of these bonds breaks them down into individual monosaccharides, which are the simplest form of carbohydrates. Understanding the structure and function of glycosidic bonds is essential for analyzing carbohydrate chemistry.
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Glycosidic Linkage Formation Concept 1

Hydrolysis

Hydrolysis is a chemical reaction that involves the breaking of a bond in a molecule using water. In carbohydrate chemistry, hydrolysis of glycosidic bonds leads to the release of monosaccharides from polysaccharides or oligosaccharides. This process is crucial for understanding how complex carbohydrates are metabolized and utilized by living organisms.
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Acidic Hydrolysis Concept 1

Fischer Projections

Fischer projections are a two-dimensional representation of three-dimensional organic molecules, particularly useful for depicting the stereochemistry of carbohydrates. In these projections, the carbon skeleton is arranged vertically, with functional groups extending horizontally. Drawing Fischer projections for monosaccharides allows for a clear visualization of their structural configuration, including the orientation of hydroxyl groups and the anomeric carbon.
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Related Practice
Textbook Question

Are one or more of the disaccharides maltose, lactose, cellobiose, and sucrose part of the trisaccharide in Problem 20.23? If so, identify which disaccharide and its location. (Hint: Look for an α-1,4 link, β-1,4 link, or 1,2 link, and then determine if the correct monosaccharides are present.)

Textbook Question

Consider the trisaccharide A, B, C shown in Problem 20.23.

a. Identify the hemiacetal and acetal linkages.

Textbook Question

Classify the four carbohydrates (a)–(d) by indicating the nature of the carbonyl group and the number of carbon atoms present. For example, glucose is an aldohexose.

c.

Textbook Question

Consider the trisaccharide A, B, C shown in Problem 20.23.

c. State the numbers of the carbon atoms that form glycosidic linkages between monosaccharide A and monosaccharide B.

Textbook Question

Identify the following as diastereomers, enantiomers, and/or anomers.

(a) β-D-fructose and β-D-fructose

(b) D-galactose and L-galactose

(c) L-allose and D-glucose (both aldohexoses)

Textbook Question

In solution, glucose exists predominantly in the cyclic hemiacetal form, which does not contain an aldehyde group. How is it possible for mild oxidizing agents to oxidize glucose?