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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2:04 minutes

Problem 17b

Textbook Question

Use the structure of d-galactose in Problem 6.15 to answer the following:

(b) Draw the Fischer projection of L-galactose.

Verified step by step guidance

Understand the structure of D-galactose: D-galactose is an aldohexose, meaning it has six carbon atoms and an aldehyde functional group. In the Fischer projection, the hydroxyl (-OH) groups are arranged in a specific orientation around the chiral carbons.

Recall the relationship between D- and L-forms of sugars: The L-form of a sugar is the mirror image of the D-form. This means that the configuration of the hydroxyl groups on each chiral carbon is reversed in the L-form compared to the D-form.

Identify the chiral centers in D-galactose: D-galactose has four chiral centers (carbon atoms 2, 3, 4, and 5). The orientation of the hydroxyl groups at these positions determines the stereochemistry of the molecule.

Reverse the configuration of the hydroxyl groups: To draw L-galactose, reverse the positions of the hydroxyl groups on each chiral center in the Fischer projection of D-galactose. For example, if the hydroxyl group is on the right in the D-form, it will be on the left in the L-form.

Draw the Fischer projection of L-galactose: Arrange the carbon chain vertically, with the aldehyde group at the top (C1) and the CH2OH group at the bottom (C6). Place the hydroxyl groups in their reversed positions compared to D-galactose, ensuring the mirror image configuration is accurately represented.

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Key Concepts

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

Fischer Projection

The Fischer projection is a two-dimensional representation of a molecule, particularly used for carbohydrates and amino acids. In this format, the vertical lines represent bonds that are oriented away from the viewer, while horizontal lines represent bonds that are coming towards the viewer. This method helps in visualizing the stereochemistry of chiral centers in a compound.

D-Galactose Structure

D-Galactose is a monosaccharide that is an epimer of glucose, differing at one specific carbon atom. It has a six-carbon structure (C6H12O6) and is an important component of lactose. Understanding its structure is crucial for drawing its stereoisomer, L-galactose, as it involves recognizing the orientation of hydroxyl groups around the chiral centers.

Stereochemistry

Stereochemistry is the study of the spatial arrangement of atoms in molecules and how this affects their chemical properties and reactions. In carbohydrates like galactose, stereochemistry is vital for distinguishing between different isomers, such as D and L forms, which have different biological activities. Recognizing the importance of stereochemistry is essential for accurately drawing and interpreting molecular structures.

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