Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

5. Chirality

Optical Activity

Organic Chemistry

5. Chirality

Optical Activity

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4:07 minutes

Problem 1

Textbook Question

Draw the mirror images of glucose and fructose. Are glucose and fructose chiral? Do you expect them to be optically active?

Verified step by step guidance

Step 1: Understand the structures of glucose and fructose. Glucose is an aldohexose (a six-carbon sugar with an aldehyde group), while fructose is a ketohexose (a six-carbon sugar with a ketone group). Both are monosaccharides and have multiple chiral centers.

Step 2: To draw the mirror images of glucose and fructose, invert the configuration of each chiral center in their structures. For example, if a hydroxyl group (-OH) is on the right side in the original structure, place it on the left side in the mirror image.

Step 3: Analyze chirality. A molecule is chiral if it has at least one chiral center and lacks an internal plane of symmetry. Both glucose and fructose have multiple chiral centers, making them chiral molecules.

Step 4: Determine optical activity. Chiral molecules are typically optically active, meaning they can rotate plane-polarized light. Since glucose and fructose are chiral, they are expected to be optically active.

Step 5: Note that the images provided show D-galactose and D-mannose, which are stereoisomers of glucose. These structures can help you understand how to invert configurations to draw mirror images for glucose and fructose.

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Key Concepts

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

Chirality

Chirality refers to the geometric property of a molecule that makes it non-superimposable on its mirror image. A chiral molecule typically has at least one carbon atom bonded to four different substituents, resulting in two distinct forms known as enantiomers. Glucose and fructose each contain multiple chiral centers, making them chiral compounds.

Optical Activity

Optical activity is the ability of a chiral compound to rotate the plane of polarized light. This property arises from the asymmetry of chiral molecules, which interact differently with light. Since both glucose and fructose are chiral, they are expected to be optically active, meaning they will rotate polarized light in specific directions.

Structural Isomers

Structural isomers are compounds that have the same molecular formula but differ in the arrangement of atoms. Glucose and fructose are structural isomers of each other, as they both share the formula C6H12O6 but have different structural configurations. Understanding their structural differences is crucial for analyzing their properties, including chirality and optical activity.

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Related Practice

Textbook Question

Calculate the specific rotations of the following samples taken at 25 °C using the sodium D line.

a. 1.00 g of sample is dissolved in 20.0 mL of ethanol. Then 5.00 mL of this solution is placed in a 20.0-cm polarimeter tube. The observed rotation is 1.25° counterclockwise.

Textbook Question

Calculate the specific rotations of the following samples taken at 25 °C using the sodium D line.

b. 0.050 g of sample is dissolved in 2.0 mL of ethanol, and this solution is placed in a 2.0-cm polarimeter tube. The observed rotation is clockwise 0.043°.

Textbook Question

If you had the two enantiomers of carvone in unmarked bottles, could you use just your nose and a polarimeter to determine

a. whether it is the (+) or (−) enantiomer that smells like spearmint

b. whether it is the (R) or (S) enantiomer that smells like spearmint?

c. With the information given in the drawings of carvone above, what can you add to your answers to (a) and (b)?