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

9. Alkenes and Alkynes

Zaitsev Rule

Organic Chemistry

9. Alkenes and Alkynes

Zaitsev Rule

Previous problemNext problem

5:18 minutes

Problem 25a,b

Textbook Question

Which alkyl halide in each pair is more reactive in an E2 reaction with hydroxide ion?
a.
b.

Verified step by step guidance

Step 1: Understand the E2 reaction mechanism. E2 reactions are bimolecular elimination reactions where a base (such as hydroxide ion) removes a proton from a β-carbon, and a leaving group (such as bromine) departs from the α-carbon, forming a double bond.

Step 2: Analyze the first pair of alkyl halides. The first structure has bromine attached to a secondary carbon, while the second structure has bromine attached to a tertiary carbon. In E2 reactions, tertiary alkyl halides are generally more reactive due to the stability of the transition state and the ability to form a more substituted alkene.

Step 3: Analyze the second pair of alkyl halides. The first structure has bromine attached to a carbon adjacent to a double bond (allylic position), while the second structure has bromine attached to a carbon that is not adjacent to a double bond. Allylic halides are more reactive in E2 reactions because the resulting double bond can be stabilized by resonance.

Step 4: Consider steric hindrance and base accessibility. In the first pair, the tertiary alkyl halide may have slightly more steric hindrance, but this is outweighed by the increased reactivity due to the formation of a more substituted alkene. In the second pair, the allylic halide is favored due to resonance stabilization.

Step 5: Conclude that for the first pair, the tertiary alkyl halide is more reactive in an E2 reaction. For the second pair, the allylic halide is more reactive in an E2 reaction due to resonance stabilization of the product.

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.

E2 Reaction Mechanism

The E2 (bimolecular elimination) reaction is a concerted process where a base removes a proton from a β-carbon while a leaving group departs from the α-carbon, resulting in the formation of a double bond. The reaction rate depends on the concentration of both the alkyl halide and the base, making it a second-order reaction. Understanding the mechanism is crucial for predicting which alkyl halide will react more readily.

Alkyl Halide Structure

The structure of alkyl halides significantly influences their reactivity in E2 reactions. Steric hindrance, which arises from bulky groups around the reactive site, can impede the approach of the base. Generally, tertiary alkyl halides are more reactive than secondary, and primary halides are the least reactive due to their steric and electronic environments.

Base Strength and Nucleophilicity

The strength of the base used in an E2 reaction plays a critical role in determining the reaction's rate and outcome. Strong bases, such as hydroxide ions, are more effective at abstracting protons, facilitating the elimination process. The choice of base can also influence the regioselectivity of the reaction, making it essential to consider when evaluating the reactivity of different alkyl halides.

Watch next

Master Defining Zaitsev’s Rule with a bite sized video explanation from Johnny

Start learning

Related Videos

Related Practice

Textbook Question

Draw the major product obtained when each of the following alkyl halides undergoes an E2 reaction:

Textbook Question

Predict the major product(s) of the following elimination reactions, paying close attention to the stereochemical outcome of the reactions.

(b)

Textbook Question

a. What is the major product obtained when each of the following compounds undergoes an E2 reaction with methoxide ion? Show the configuration of the product.

b. Does the product obtained depend on whether you start with the R or S enantiomer of the reactant?

Textbook Question

Which alkyl halide in each pair is more reactive in an E2 reaction with hydroxide ion?

Textbook Question

Which alkyl halide in each pair is more reactive in an E2 reaction with hydroxide ion?

Textbook Question

For each of the following alkyl halides, indicate the stereoisomer that would be obtained in greatest yield in an E2 reaction.

c. 3-bromo-2,3-dimethylpentane

d. 3-bromo-3,4-dimethylhexane

Textbook Question

For each of the following alkyl halides, indicate the stereoisomer that would be obtained in greatest yield in an E2 reaction.

d. 3-bromo-3,4-dimethylhexane

Textbook Question

What is the major product formed when the following compounds undergo an E1 reaction?

Show more practices

Download the Mobile app

Privacy

Do not sell my personal information

Accessibility

Patent notice

Sitemap

Which alkyl halide in each pair is more reactive in an E2 reaction with hydroxide ion?a. b.

Key Concepts

E2 Reaction Mechanism

Alkyl Halide Structure

Base Strength and Nucleophilicity

Watch next

Which alkyl halide in each pair is more reactive in an E2 reaction with hydroxide ion?
a.
b.