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

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2:50 minutes

Problem 83b

Textbook Question

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

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Identify the alkyl halide structure and determine the type of halide (primary, secondary, or tertiary). This classification will help predict the reactivity and the stability of the intermediate formed during the E2 reaction.

Recall the mechanism of an E2 reaction: it is a single-step, concerted elimination process where a strong base abstracts a proton (β-hydrogen) from the β-carbon, and the leaving group (halide) departs simultaneously, forming a double bond.

Determine the β-hydrogens available on the β-carbons adjacent to the carbon bearing the halide. If there are multiple β-carbons, consider the regioselectivity of the reaction (Zaitsev's rule), which states that the more substituted alkene is usually the major product.

Consider the stereochemistry of the elimination. For an E2 reaction, the β-hydrogen and the leaving group must be antiperiplanar (in opposite planes and aligned 180° apart). If necessary, rotate the molecule to visualize this geometry.

Draw the major product by forming a double bond between the α-carbon (the carbon bonded to the halide) and the β-carbon from which the β-hydrogen was removed. Ensure the product follows Zaitsev's rule unless steric hindrance or other factors favor the Hofmann product (less substituted alkene).

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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 type of elimination reaction where a base removes a proton from a β-carbon while a leaving group departs from the α-carbon simultaneously. This concerted mechanism results in the formation of a double bond between the α and β carbons. Understanding the stereochemistry and the requirement for anti-periplanar geometry is crucial for predicting the major product.

Alkyl Halides

Alkyl halides are organic compounds containing a carbon atom bonded to a halogen atom (F, Cl, Br, I). Their structure influences reactivity in elimination reactions, with primary, secondary, and tertiary classifications affecting the pathway taken. Tertiary alkyl halides are more likely to undergo E2 reactions due to steric hindrance, while primary halides may favor substitution reactions instead.

Base Strength and Sterics

The strength and steric properties of the base used in an E2 reaction significantly influence the reaction's outcome. Strong bases, such as alkoxides or hydrides, are typically required to facilitate the elimination process. Additionally, bulky bases can lead to different regioselectivity and stereoselectivity in the products, making the choice of base critical for predicting the major product formed.

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Textbook Question

What is the major elimination product obtained from an E2 reaction of each of the following alkyl halides with hydroxide ion?

Textbook Question

What is the major elimination product obtained from an E2 reaction of each of the following alkyl halides with hydroxide ion?

Textbook Question

What products will be obtained from the E2 reaction of the following alkyl halides?

Textbook Question

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

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?

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

Key Concepts

E2 Reaction Mechanism

Alkyl Halides

Base Strength and Sterics

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