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Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
All textbooksMullins 1st EditionCh. 27 - Carbohydrates, Nucleic Acids, and LipidsProblem 10a
Chapter 26, Problem 10a

Categorize the following monosaccharides as d or l.
(a) Structural formula of a monosaccharide showing hydroxyl groups and a carbonyl group for D and L isomerism classification.

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1
Identify the chiral center farthest from the carbonyl group in the monosaccharide. In this structure, the chiral center is the carbon atom bonded to the OH group at the bottom of the Fischer projection.
Determine the orientation of the hydroxyl group (OH) attached to this chiral center. In a Fischer projection, if the OH group is on the right, the sugar is classified as a D-sugar. If the OH group is on the left, it is classified as an L-sugar.
In the given structure, observe that the OH group on the chiral center farthest from the carbonyl group is on the left side.
Based on the orientation of the OH group, classify the monosaccharide. Since the OH group is on the left, this monosaccharide is an L-sugar.
Conclude that the given monosaccharide is categorized as an L-monosaccharide based on the position of the OH group in the Fischer projection.

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Key Concepts

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

D and L Configuration

The D and L notation refers to the configuration of monosaccharides based on the orientation of the hydroxyl group (-OH) on the chiral carbon farthest from the carbonyl group. If the -OH group is on the right in a Fischer projection, the sugar is classified as D; if it is on the left, it is classified as L. This system helps in distinguishing between different stereoisomers of sugars.
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Fischer Projection

A Fischer projection is a two-dimensional representation of a three-dimensional organic molecule, particularly useful for depicting the stereochemistry of sugars. In this format, vertical lines represent bonds that project away from the viewer, while horizontal lines represent bonds that project towards the viewer. Understanding Fischer projections is essential for determining the D or L configuration of monosaccharides.
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Monosaccharide Structure

Monosaccharides are the simplest form of carbohydrates, consisting of a single sugar unit with a general formula of (CH2O)n. They can exist in linear or cyclic forms and contain functional groups such as aldehydes or ketones. Recognizing the structure of monosaccharides is crucial for categorizing them as D or L, as it involves identifying the correct chiral center and its substituents.
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Related Practice
Textbook Question

Convert each line-angle drawing, using appropriate bond rotations, into a correct Fischer projection.

(c)

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Textbook Question

Convert each line-angle drawing, using appropriate bond rotations, into a correct Fischer projection.

(a)

1
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Textbook Question

Draw the structure of and name the enantiomeric diols that result from the cis-dihydroxylation of the alkene shown.

6
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Textbook Question

Which of the following molecule pairs are epimers?

(a)

(b)

(c)

Textbook Question

Convert each line-angle drawing, using appropriate bond rotations, into a correct Fischer projection.

(b)

1
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Textbook Question

Using the Haworth projection, draw the furanose ring that would form between the C5 hydroxyl group and the ketone at C2 for the molecule shown.

2
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