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

Acetal Protecting Group

Organic Chemistry

21. Aldehydes and Ketones: Nucleophilic Addition

Acetal Protecting Group

Previous problem

9:16 minutes

Problem 8

Textbook Question

Rationalize the difference in Kₑq for the following reactions. Be sure to account for both ∆S and ∆H.

Verified step by step guidance

Begin by understanding the concept of equilibrium constant (Kₑq). It is a measure of the extent of a chemical reaction at equilibrium, and it is influenced by the changes in enthalpy (∆H) and entropy (∆S) of the reaction.

Recall the Gibbs free energy equation:

Δ G = Δ H - T Δ S

. This equation relates the change in Gibbs free energy (∆G) to the changes in enthalpy (∆H) and entropy (∆S), where T is the temperature in Kelvin.

Understand that the equilibrium constant Kₑq is related to Gibbs free energy by the equation:

K = e^{- Δ G / RT}

, where R is the universal gas constant. This shows that Kₑq is exponentially dependent on ∆G.

Analyze how ∆H and ∆S affect ∆G. A negative ∆H (exothermic reaction) tends to favor product formation, increasing Kₑq, while a positive ∆S (increase in disorder) also favors product formation, increasing Kₑq. Conversely, a positive ∆H or negative ∆S would decrease Kₑq.

Compare the reactions by evaluating their ∆H and ∆S values. Consider how these values influence ∆G and subsequently Kₑq. A reaction with a more negative ∆G will have a larger Kₑq, indicating a greater extent of reaction towards products at equilibrium.

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Key Concepts

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

Equilibrium Constant (Kₑq)

The equilibrium constant, Kₑq, is a measure of the ratio of the concentrations of products to reactants at equilibrium for a given reaction. It reflects the extent to which a reaction proceeds and is influenced by temperature and the nature of the reactants and products. A higher Kₑq indicates a greater concentration of products relative to reactants at equilibrium.

Enthalpy Change (∆H)

Enthalpy change, ∆H, represents the heat absorbed or released during a chemical reaction at constant pressure. It is a key factor in determining the favorability of a reaction; exothermic reactions (negative ∆H) tend to be more favorable as they release energy, while endothermic reactions (positive ∆H) require energy input. ∆H influences the equilibrium position by affecting the energy balance of the reaction.

Entropy Change (∆S)

Entropy change, ∆S, measures the change in disorder or randomness in a system during a chemical reaction. A positive ∆S indicates an increase in disorder, which can favor the spontaneity of a reaction. Entropy is a crucial component of the Gibbs free energy equation, which determines the spontaneity of a reaction. ∆S, along with ∆H, affects the equilibrium constant by influencing the overall energy dynamics of the reaction.

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