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Ch. 24 - Amino Acids, Peptides, and Proteins
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
All textbooksWade 9th EditionCh. 24 - Amino Acids, Peptides, and ProteinsProblem 48d,e
Chapter 24, Problem 48d,e

Use Figure 23-3 (the D family of aldoses) to name the following aldoses.
(d) the enantiomer of D-galactose
(e) the C5 epimer of D-glucose
Diagram of aldoses showing D-glyceraldehyde and its enantiomers, including D-galactose and C5 epimer of D-glucose.

Verified step by step guidance
1
Identify the structure of D-galactose from Figure 23-3. D-galactose is an aldohexose with the specific configuration of hydroxyl groups on its chiral centers.
To find the enantiomer of D-galactose, invert the configuration at every chiral center. This means if a hydroxyl group is on the right in D-galactose, it should be on the left in its enantiomer, and vice versa.
Name the enantiomer of D-galactose. Since enantiomers are mirror images, the enantiomer of D-galactose is L-galactose.
Identify the structure of D-glucose from Figure 23-3. D-glucose is also an aldohexose with its own specific configuration of hydroxyl groups.
To find the C5 epimer of D-glucose, change the configuration of the hydroxyl group at the C5 position only, while keeping the rest of the molecule the same. The C5 epimer of D-glucose is D-mannose.

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Key Concepts

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

Aldoses

Aldoses are a type of monosaccharide characterized by the presence of an aldehyde group (-CHO) at one end of the molecule. They can exist in various forms, including D and L configurations, which refer to the orientation of the hydroxyl group on the chiral carbon farthest from the aldehyde. Understanding aldoses is crucial for identifying their structural relationships and naming conventions.
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Enantiomers

Enantiomers are a pair of molecules that are non-superimposable mirror images of each other. In the context of sugars, D-galactose and its enantiomer, L-galactose, differ in the configuration around all chiral centers. Recognizing enantiomers is essential for naming aldoses correctly, as it affects their biochemical properties and interactions.
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Epimers

Epimers are a specific type of diastereomer that differ in configuration at only one of several chiral centers. For example, D-glucose and D-mannose are C2 epimers, while D-glucose and D-galactose are C4 epimers. Identifying epimers is important for understanding the structural diversity of sugars and their relationships, particularly when naming aldoses based on their stereochemistry.
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Related Practice
Textbook Question

There are many methods for activating a carboxylic acid in preparation for coupling with an amine. The following method converts the acid to an N-hydroxysuccinimide (NHS) ester.

(b) Propose a mechanism for the reaction shown.

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Textbook Question

Sometimes chemists need the unnatural D enantiomer of an amino acid, often as part of a drug or an insecticide. Most L-amino acids are isolated from proteins, but the D-amino acids are rarely found in natural proteins. D-amino acids can be synthesized from the corresponding L-amino acids. The following synthetic scheme is one of the possible methods.

(a) Draw the structures of intermediates 1 and 2 in this scheme.

(b) How do we know that the product is entirely the unnatural D configuration?

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Textbook Question

There are many methods for activating a carboxylic acid in preparation for coupling with an amine. The following method converts the acid to an N-hydroxysuccinimide (NHS) ester.

(c) Propose a mechanism for the reaction of the NHS ester with an amine, R–NH2.

546
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