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

E1 Reaction

Organic Chemistry

8. Elimination Reactions

E1 Reaction

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6:48 minutes

Problem 90

Textbook Question

a. Which reacts faster in an E2 reaction: 3-bromocyclohexene or bromocyclohexane?
b. Which reacts faster in an E1 reaction?

Verified step by step guidance

Step 1: Understand the E2 reaction mechanism. The E2 reaction is a bimolecular elimination reaction where the rate depends on both the substrate and the base. It requires a strong base and a good leaving group. The reaction proceeds via a single concerted step, and the geometry of the β-hydrogens (anti-periplanar to the leaving group) is critical.

Step 2: Analyze the structure of 3-bromocyclohexene. In this molecule, the bromine atom is attached to a cyclohexene ring. The double bond in the cyclohexene ring introduces rigidity, which can influence the anti-periplanar geometry required for the E2 reaction.

Step 3: Analyze the structure of bromocyclohexane. In this molecule, the bromine atom is attached to a cyclohexane ring. The absence of a double bond allows for more conformational flexibility, which can make it easier to achieve the anti-periplanar geometry required for the E2 reaction.

Step 4: Compare the two molecules for the E2 reaction. The rigidity of the double bond in 3-bromocyclohexene may hinder the anti-periplanar geometry, making bromocyclohexane react faster in an E2 reaction.

Step 5: For the E1 reaction, consider the stability of the carbocation intermediate. The E1 reaction proceeds via a two-step mechanism where the leaving group departs first, forming a carbocation. The double bond in 3-bromocyclohexene can stabilize the carbocation through resonance, making it react faster in an E1 reaction compared to bromocyclohexane.

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Key Concepts

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

E2 Reaction Mechanism

The E2 (bimolecular elimination) reaction is a concerted process where a base abstracts a proton while a leaving group departs, resulting in the formation of a double bond. The rate of an E2 reaction depends on the strength of the base and the structure of the substrate. Steric hindrance and the stability of the transition state play crucial roles, with more substituted substrates typically reacting faster.

E1 Reaction Mechanism

The E1 (unimolecular elimination) reaction involves two steps: first, the formation of a carbocation intermediate after the leaving group departs, followed by deprotonation to form a double bond. The rate of an E1 reaction is primarily dependent on the stability of the carbocation formed. Tertiary carbocations are more stable and thus react faster in E1 mechanisms compared to primary or secondary ones.

Substrate Structure and Reactivity

The structure of the substrate significantly influences the reactivity in both E1 and E2 reactions. In E2 reactions, steric factors and the ability to form a stable transition state are critical, while in E1 reactions, the stability of the carbocation intermediate is paramount. For example, cyclohexene derivatives may exhibit different reactivity patterns based on their ring strain and substitution, affecting the overall reaction rate.

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