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

8. Elimination Reactions

SN1 SN2 E1 E2 Chart (Big Daddy Flowchart)

Organic Chemistry

8. Elimination Reactions

SN1 SN2 E1 E2 Chart (Big Daddy Flowchart)

Previous problemNext problem

4:33 minutes

Problem 50e

Textbook Question

For which of the following reactions would you expect elimination to be more favored than substitution?
(e)

Verified step by step guidance

Step 1: Analyze the reaction conditions for each case. The first reaction uses NaSCH₃ in DMSO, which is a strong nucleophile and a polar aprotic solvent. The second reaction uses NaOEt in EtOH, which is a strong base and a polar protic solvent.

Step 2: Understand the role of the solvent. Polar aprotic solvents like DMSO favor substitution reactions (S_N2 mechanism) because they stabilize the transition state without stabilizing the nucleophile. Polar protic solvents like EtOH favor elimination reactions (E2 mechanism) because they stabilize the base and promote proton abstraction.

Step 3: Consider the nucleophile/base. NaSCH₃ is a strong nucleophile but a weak base, favoring substitution over elimination. NaOEt is both a strong nucleophile and a strong base, favoring elimination over substitution.

Step 4: Evaluate the structure of the substrate. Both substrates are secondary alkyl halides, which can undergo either substitution or elimination. However, elimination is more likely when a strong base is present, as in the second reaction.

Step 5: Conclude that elimination is more favored in the second reaction (NaOEt/EtOH) due to the combination of a strong base and polar protic solvent, which promotes the E2 mechanism.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

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

Elimination vs. Substitution Reactions

In organic chemistry, elimination reactions involve the removal of atoms or groups from a molecule, resulting in the formation of a double bond or a ring structure. In contrast, substitution reactions replace one atom or group with another. The preference for elimination over substitution often depends on factors such as the structure of the substrate, the nature of the leaving group, and the reaction conditions.

Solvent Effects

The choice of solvent can significantly influence the outcome of a reaction. Polar aprotic solvents, like DMSO, favor elimination reactions by stabilizing the transition state and promoting the formation of alkenes. Conversely, polar protic solvents, such as ethanol, tend to stabilize carbocations, which can lead to substitution reactions. Understanding solvent effects is crucial for predicting reaction pathways.

Nucleophilicity and Basicity

Nucleophilicity refers to the ability of a species to donate an electron pair to form a bond, while basicity measures the tendency of a species to accept protons. Strong bases are typically better nucleophiles and favor elimination reactions, especially in the presence of a good leaving group. In the given reactions, the nucleophiles (NaSCH3 and NaOEt) differ in their basicity, influencing whether elimination or substitution is favored.

Watch next

Master Overview of the flowchart. with a bite sized video explanation from Johnny

Start learning