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

Fischer Projections

GOB Chemistry

20. Carbohydrates

Fischer Projections

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3:47 minutes

Problem 65

Textbook Question

What are the differences in the Fischer projections of d-fructose and d-galactose?

Verified step by step guidance

Understand the Fischer projection: A Fischer projection is a two-dimensional representation of a molecule's three-dimensional structure, commonly used for carbohydrates. The vertical lines represent bonds going into the plane (away from the viewer), and the horizontal lines represent bonds coming out of the plane (toward the viewer). The most oxidized carbon is placed at the top.

Identify the structure of D-fructose: D-fructose is a ketohexose, meaning it has six carbons and a ketone functional group. In its Fischer projection, the ketone group is located at the second carbon (C2), and the hydroxyl (-OH) groups on the remaining carbons are arranged in a specific pattern.

Identify the structure of D-galactose: D-galactose is an aldohexose, meaning it has six carbons and an aldehyde functional group. In its Fischer projection, the aldehyde group is located at the first carbon (C1), and the hydroxyl (-OH) groups on the remaining carbons are arranged in a specific pattern.

Compare the functional groups: The key difference between D-fructose and D-galactose is the type and position of the carbonyl group. D-fructose has a ketone group at C2, while D-galactose has an aldehyde group at C1.

Compare the hydroxyl group arrangements: The arrangement of the hydroxyl (-OH) groups on the chiral carbons (C3, C4, and C5) differs between D-fructose and D-galactose. Carefully examine the Fischer projections to identify the specific differences in the orientation of these groups.

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Key Concepts

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

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, vertical lines represent bonds that extend away from the viewer, while horizontal lines indicate bonds that come towards the viewer. This format helps in visualizing the spatial arrangement of atoms and functional groups in sugars.

D-Fructose Structure

D-fructose is a ketohexose, meaning it contains six carbon atoms and a ketone functional group. In its Fischer projection, the carbonyl group is located at the second carbon atom, and it has a specific arrangement of hydroxyl groups that distinguishes it from other sugars. Understanding its structure is crucial for comparing it with other carbohydrates, such as D-galactose.

D-Galactose Structure

D-galactose is an aldohexose, which means it has six carbon atoms and an aldehyde functional group. In its Fischer projection, the carbonyl group is at the first carbon atom, and the arrangement of hydroxyl groups differs from that of D-fructose. Recognizing these structural differences is essential for understanding the distinct properties and functions of these two sugars.

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Textbook Question

Draw the Fischer projection for each of the following wedge–dash structures:

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Textbook Question

Draw the Fischer projection for each of the following wedge–dash structures:

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Textbook Question

An infant with galactosemia can utilize D-glucose in milk but not d-galactose. How does the Fischer projection of D-galactose differ from that of D-glucose?

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Textbook Question

D-Fructose is the sweetest monosaccharide. How does the Fischer projection of D-fructose differ from that of D-glucose?

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Textbook Question

On an exam, a student was asked to draw the Fischer projection of L-glucose, but he had only memorized the structure of D-glucose. He wrote the structure of D-glucose and switched the hydroxyl group on C5 from the right to the left. Was his answer correct? If not, what is the name of the aldose that he drew?

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Textbook Question

Draw the structures of a ketohexose.

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Textbook Question

How many chiral carbon atoms are present in each of the molecules shown in Problem 20.31?

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Textbook Question

Draw the open-chain structure of a 4-carbon deoxy sugar.