Table of contents

1. Matter and Measurements4h 31m
2. Atoms and the Periodic Table5h 23m
3. Ionic Compounds2h 18m
4. Molecular Compounds2h 18m
5. Classification & Balancing of Chemical Reactions3h 17m
6. Chemical Reactions & Quantities2h 27m
7. Energy, Rate and Equilibrium3h 46m
8. Gases, Liquids and Solids3h 25m
9. Solutions4h 10m
10. Acids and Bases3h 29m
11. Nuclear Chemistry56m
BONUS: Lab Techniques and Procedures1h 38m
BONUS: Mathematical Operations and Functions47m
12. Introduction to Organic Chemistry1h 34m
13. Alkenes, Alkynes, and Aromatic Compounds2h 12m
14. Compounds with Oxygen or Sulfur1h 6m
15. Aldehydes and Ketones1h 1m
16. Carboxylic Acids and Their Derivatives1h 11m
17. Amines39m
18. Amino Acids and Proteins1h 51m
19. Enzymes1h 37m
20. Carbohydrates1h 41m
21. The Generation of Biochemical Energy2h 8m
22. Carbohydrate Metabolism2h 22m
23. Lipids2h 26m
24. Lipid Metabolism1h 45m
25. Protein and Amino Acid Metabolism1h 37m
26. Nucleic Acids and Protein Synthesis2h 54m

20. Carbohydrates

D vs L Enantiomers

GOB Chemistry

20. Carbohydrates

D vs L Enantiomers

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1:18 minutes

Problem 17a

Textbook Question

Identify each of the following as D or L:
a.

Verified step by step guidance

Step 1: Understand the D and L notation. The D and L system is used to describe the configuration of chiral molecules, particularly sugars and amino acids. It is based on the molecule's relationship to glyceraldehyde, the simplest chiral sugar. D and L do not refer to the direction of optical rotation but to the spatial arrangement of groups around the chiral carbon.

Step 2: Locate the chiral carbon farthest from the carbonyl group (C=O) in the molecule. This carbon is the reference point for determining whether the molecule is D or L.

Step 3: Examine the orientation of the hydroxyl group (-OH) attached to the reference chiral carbon. If the -OH group is on the right side of the Fischer projection, the molecule is classified as D. If the -OH group is on the left side, the molecule is classified as L.

Step 4: Carefully analyze the Fischer projection of the molecule provided in the image. Identify the position of the -OH group on the reference chiral carbon.

Step 5: Based on the position of the -OH group, assign the molecule as either D or L. If the -OH is on the right, it is D; if it is on the left, it is L.

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Key Concepts

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

D and L Stereochemistry

D and L refer to the stereochemical configuration of molecules, particularly amino acids and sugars. 'D' (dextrorotatory) indicates that a molecule rotates plane-polarized light to the right, while 'L' (levorotatory) indicates a leftward rotation. This classification is based on the molecule's relationship to glyceraldehyde, with D and L designations corresponding to the orientation of the hydroxyl group on the penultimate carbon.

Chirality

Chirality is a property of a molecule that makes it non-superimposable on its mirror image, much like left and right hands. Chiral molecules often exist in two forms, known as enantiomers, which can have different biological activities. Understanding chirality is crucial for determining the D or L configuration of a compound, as it influences how the molecule interacts with biological systems.

Fischer Projection

The Fischer projection is a two-dimensional representation of a three-dimensional organic molecule, commonly used for sugars and amino acids. In this format, the vertical lines represent bonds going back in space, while horizontal lines represent bonds coming forward. This method simplifies the visualization of stereochemistry, making it easier to identify whether a compound is in the D or L configuration based on the orientation of its functional groups.

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