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

21. Aldehydes and Ketones: Nucleophilic Addition

Imine vs Enamine

Organic Chemistry

21. Aldehydes and Ketones: Nucleophilic Addition

Imine vs Enamine

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3:18 minutes

Problem 29

Textbook Question

What is the specific rotation of an equilibrium mixture of fructose? (Hint: Recall that the specific rotation of an equilibrium mixture of glucose is +52.7.)

Verified step by step guidance

Understand the concept of specific rotation: Specific rotation ([α]) is a physical property that measures the degree to which a chiral compound rotates plane-polarized light. It is defined as [α] = (α_obs) / (l × c), where α_obs is the observed rotation, l is the path length in decimeters, and c is the concentration in g/mL.

Recall that the specific rotation of an equilibrium mixture is the weighted average of the specific rotations of the individual components in the mixture, based on their relative proportions at equilibrium.

Identify the specific rotation of pure fructose and pure glucose. For glucose, the specific rotation is given as +52.7. You will need to know the specific rotation of pure fructose (commonly -92.4) to proceed.

Determine the equilibrium proportions of glucose and fructose in the mixture. This information is typically provided in the problem or can be derived from equilibrium constants if given.

Calculate the specific rotation of the equilibrium mixture using the formula: [α]_mixture = (fraction_glucose × [α]_glucose) + (fraction_fructose × [α]_fructose). Substitute the known values for the specific rotations and the equilibrium fractions to find the result.

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Key Concepts

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

Specific Rotation

Specific rotation is a property of chiral compounds that quantifies the degree to which they rotate plane-polarized light. It is defined as the observed rotation of light at a specific wavelength and temperature, normalized to a concentration of 1 g/mL in a 1 dm path length. This property is crucial for characterizing sugars and other optically active substances.

Equilibrium Mixture

An equilibrium mixture refers to a state where two or more forms of a compound coexist in a dynamic balance, such as different anomers or stereoisomers of sugars. In the case of fructose, it can exist in various forms, and the specific rotation of the mixture will depend on the proportions of these forms present at equilibrium.

Optical Activity of Sugars

Sugars like fructose and glucose exhibit optical activity due to their chiral centers, which means they can rotate plane-polarized light in different directions. The specific rotation of a sugar solution can vary based on the sugar's structure and the concentration of its different forms, making it essential to understand how these factors influence the overall optical activity in mixtures.

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