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

7. Substitution Reactions

Substitution Comparison

Organic Chemistry

7. Substitution Reactions

Substitution Comparison

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1:34 minutes

Problem 56d,e

Textbook Question

Which reaction in each of the following pairs takes place more rapidly? (EtOH is ethyl alcohol; Et₂O is diethyl ether.)
d.
e.

Verified step by step guidance

Step 1: Analyze the reaction mechanism for each pair of reactions. For part (d), consider the nucleophilic substitution reactions (SN2 or SN1) and the solvent effects. DMSO is a polar aprotic solvent, which favors SN2 reactions by stabilizing the transition state without solvating the nucleophile. EtOH, on the other hand, is a polar protic solvent, which can solvate the nucleophile and slow down SN2 reactions.

Step 2: Compare the nucleophiles in part (d). HO⁻ is a strong nucleophile, and its reactivity will be influenced by the solvent. In DMSO, HO⁻ remains highly reactive, while in EtOH, its reactivity is reduced due to solvation. This suggests that the reaction in DMSO will proceed more rapidly.

Step 3: For part (e), examine the reaction between CH3Br and NH3. NH3 acts as a nucleophile, and the solvent plays a role in determining the reaction rate. Et2O is a nonpolar solvent, which does not significantly stabilize the transition state or solvate the nucleophile. EtOH, being polar protic, can solvate NH3 and reduce its nucleophilicity.

Step 4: Consider the steric and electronic effects in part (e). CH3Br is a methyl halide, which is highly reactive in SN2 reactions due to minimal steric hindrance. The solvent choice (Et2O vs. EtOH) will influence the nucleophilicity of NH3 and the overall reaction rate.

Step 5: Summarize the findings. For part (d), the reaction in DMSO is expected to be faster due to the polar aprotic nature of the solvent favoring SN2. For part (e), the reaction in Et2O is likely faster because the nonpolar solvent does not solvate NH3, allowing it to remain more nucleophilic compared to EtOH.

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Key Concepts

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

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group in a molecule by a nucleophile. The rate of these reactions can depend on the strength of the nucleophile, the nature of the leaving group, and the solvent used. In the context of the question, understanding how nucleophiles like HO− and NH3 interact with CH3Br is crucial for predicting which reaction will occur more rapidly.

Solvent Effects on Reaction Rates

The choice of solvent can significantly influence the rate of chemical reactions, particularly in nucleophilic substitutions. Polar protic solvents, like ethanol (EtOH), can stabilize ions and transition states, while polar aprotic solvents, like DMSO, can enhance nucleophilicity. Recognizing how the solvent affects the reactivity of the nucleophile and the leaving group is essential for determining the faster reaction in the pairs presented.

Leaving Group Ability

The ability of a leaving group to depart from a molecule is a key factor in determining the rate of nucleophilic substitution reactions. Good leaving groups, such as bromide (Br−), can stabilize the transition state and facilitate the reaction. In the question, comparing the reactions involving CH3Br with different nucleophiles and solvents requires an understanding of how the leaving group's characteristics influence the overall reaction kinetics.

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b. What does this result suggest about the mechanism of the reaction of 2-iodobutane with iodide ion?

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Which reaction in each of the following pairs takes place more rapidly? (EtOH is ethyl alcohol; Et2O is diethyl ether.)d. e.

Key Concepts

Nucleophilic Substitution Reactions

Solvent Effects on Reaction Rates

Leaving Group Ability

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Which reaction in each of the following pairs takes place more rapidly? (EtOH is ethyl alcohol; Et₂O is diethyl ether.)
d.
e.