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

6. Thermodynamics and Kinetics

Entropy

Organic Chemistry

6. Thermodynamics and Kinetics

Entropy

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Problem 3a

Textbook Question

Would you expect ∆S to be greater than, less than, or equal to zero in the following reactions?
a.

Verified step by step guidance

Step 1: Analyze the reaction. The reactants are acetate ion (CH3COO⁻) and ethyl bromide (CH3CH2Br). The products are ethyl acetate (CH3COOCH2CH3) and bromide ion (Br⁻). This is a nucleophilic substitution reaction.

Step 2: Consider the number of molecules involved. In the reactants, there are two separate molecules (CH3COO⁻ and CH3CH2Br). In the products, there are also two separate molecules (CH3COOCH2CH3 and Br⁻). Therefore, the number of molecules remains the same.

Step 3: Evaluate the change in molecular complexity. The reactants include a simple ion and a small organic molecule. The products include a slightly more complex organic molecule (ethyl acetate) and a simple ion (Br⁻). The molecular complexity increases slightly due to the formation of ethyl acetate.

Step 4: Consider the entropy (∆S). Entropy is a measure of disorder. Since the number of molecules remains constant and the molecular complexity increases slightly, the entropy change (∆S) is likely to be slightly negative or less than zero.

Step 5: Conclude the reasoning. Based on the analysis, ∆S is expected to be less than zero because the reaction results in a slight decrease in disorder due to the formation of a more complex molecule.

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Key Concepts

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

Entropy (∆S)

Entropy, denoted as ∆S, is a measure of the disorder or randomness in a system. In chemical reactions, an increase in the number of gas molecules or a transition from a more ordered state (like solid or liquid) to a less ordered state (like gas) typically results in a positive ∆S. Conversely, reactions that lead to a more ordered state usually have a negative ∆S.

Reaction Mechanism

The reaction mechanism describes the step-by-step process by which reactants are converted into products. Understanding the mechanism helps predict the changes in molecular structure and the resulting entropy changes. In the provided reaction, the formation of new bonds and the rearrangement of atoms can influence the overall disorder of the system.

Molecular Complexity

Molecular complexity refers to the number of atoms and the types of bonds in a molecule. Generally, as molecular complexity increases, the entropy of the system also increases due to the greater number of possible arrangements of atoms. In the given reaction, the products may have different complexities compared to the reactants, affecting the overall entropy change.

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Related Practice

Textbook Question

For the following reactions we have not seen yet, which side, if either, would be favored by increasing the temperature?

(b)

Textbook Question

Predict which side of the equilibrium is favored by ∆H, ∆G, and ∆S.

Textbook Question

For each of the following processes, indicate whether you expect ∆S° to be greater than, less than, or equal to 0. Explain your answer.

(a) Boiling water

Textbook Question

In Chapter 13, we discuss the ring-opening reactions of epoxides, such as the one shown here.

(b) Predict the sign of ∆S°.

Textbook Question

For a reaction carried out at 25 °C with an equilibrium constant of 1 × 10^-3, to increase the equilibrium constant by a factor of 10:

a. how much must ∆G° change?

b. how much must ∆H° change if ∆S° = 0 kcal mol^-1K^-1?

c. how much must ∆S° change if ∆H° = 0 kcal mol^-1?

Textbook Question

From the following rate constants, determined at five temperatures, calculate the experimental energy of activation and ∆G^‡, ∆H^‡, and ∆S^‡ for the reaction at 30 °C:

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Textbook Question

a. What is the equilibrium constant for a reaction that is carried out at 25 °C (298 K) with ∆H° = 20 kcal/mol and ∆S° = 5.0 × 10^-2 kcal mol^-1 K^-1?

b. What is the equilibrium constant for the same reaction carried out at 125 °C?

Textbook Question

(ii) Which side of the reaction is favored by entropy? (iii) If ∆S° = 0 for these reactions, calculate ∆G° (Assume T = 298 K) [BDE for O―H = 110 kcal /mol.]

(b)

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Would you expect ∆S to be greater than, less than, or equal to zero in the following reactions?a.

Key Concepts

Entropy (∆S)

Reaction Mechanism

Molecular Complexity

Watch next

Would you expect ∆S to be greater than, less than, or equal to zero in the following reactions?
a.