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

Problem 39a

Textbook Question

Would you expect the following bases to favor E1 or E2 elimination?
(a)

Verified step by step guidance

Step 1: Understand the difference between E1 and E2 elimination mechanisms. E1 elimination is a two-step process involving the formation of a carbocation intermediate, while E2 elimination is a one-step process where the base abstracts a proton and the leaving group departs simultaneously.

Step 2: Analyze the strength of the base. Strong bases typically favor E2 elimination because they can efficiently abstract a proton in a single step. Weak bases, on the other hand, are more likely to favor E1 elimination as they do not have the strength to directly abstract a proton.

Step 3: Consider the substrate structure. E1 elimination is favored by substrates that can form stable carbocations (e.g., tertiary carbons or allylic/benzylic carbons). E2 elimination is less dependent on carbocation stability and can occur with primary, secondary, or tertiary substrates.

Step 4: Evaluate steric hindrance. Bulky bases are more likely to favor E2 elimination because steric hindrance makes it difficult for them to approach the substrate closely enough to facilitate carbocation formation, which is required for E1.

Step 5: Examine reaction conditions. E1 elimination is typically favored under conditions that promote carbocation formation, such as polar protic solvents and heat. E2 elimination is favored under conditions that support strong base activity, such as polar aprotic solvents.

Verified video answer for a similar problem:

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

Play a video:

Was this helpful?

Key Concepts

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

E1 and E2 Mechanisms

E1 (unimolecular elimination) and E2 (bimolecular elimination) are two types of elimination reactions in organic chemistry. E1 involves a two-step mechanism where the leaving group departs first, forming a carbocation, followed by deprotonation to form the alkene. In contrast, E2 is a one-step mechanism where the base abstracts a proton while the leaving group departs simultaneously, leading to the formation of the alkene.

Base Strength and Sterics

The strength and steric hindrance of the base play a crucial role in determining whether an E1 or E2 mechanism will be favored. Strong bases, such as alkoxides, typically favor E2 reactions due to their ability to abstract protons quickly. Conversely, weak bases or those that are sterically hindered may lead to E1 reactions, as they are less effective at deprotonation and may allow for carbocation formation.

Substrate Structure

The structure of the substrate, particularly the degree of substitution at the carbon bearing the leaving group, influences the preference for E1 or E2 mechanisms. Tertiary substrates favor E1 due to the stability of the resulting carbocation, while primary substrates are more likely to undergo E2 elimination, as they do not stabilize carbocations effectively. Secondary substrates can lead to both mechanisms depending on the conditions.

Watch next

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

Start learning