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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3:58 minutes

Problem 116

Textbook Question

Two elimination products are obtained from the following E2 reaction:

a. What are the elimination products?
b. Which is formed in greater yield?

Verified step by step guidance

Identify the type of reaction: The problem specifies an E2 elimination reaction. In an E2 reaction, a strong base removes a β-hydrogen (a hydrogen atom on a carbon adjacent to the carbon bearing the leaving group) while the leaving group departs, forming a double bond (alkene).

Analyze the structure of the substrate: The substrate is CH3CH2CHDCH2Br. The β-hydrogens are located on the carbon adjacent to the carbon bonded to the bromine (leaving group). In this case, there are two β-hydrogens: one is a regular hydrogen (H), and the other is a deuterium (D, a heavier isotope of hydrogen).

Determine the possible elimination products: The elimination can occur in two ways, depending on which β-hydrogen is removed. If the regular hydrogen (H) is removed, the product will be CH3CH=CHD. If the deuterium (D) is removed, the product will be CH3CH=CH2. These are the two possible alkenes formed.

Consider the regioselectivity and isotope effect: The E2 reaction typically follows Zaitsev's rule, which states that the more substituted alkene is favored. However, the isotope effect must also be considered. The C-D bond is stronger than the C-H bond, so the removal of the regular hydrogen (H) is kinetically favored over the removal of deuterium (D).

Predict the major product: Based on the isotope effect, the product CH3CH=CHD (formed by removing the regular hydrogen) will be formed in greater yield compared to CH3CH=CH2 (formed by removing deuterium).

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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 mechanism where a base abstracts a proton from a β-carbon while a leaving group departs from the α-carbon, resulting in the formation of a double bond. This reaction typically requires strong bases and is characterized by a single transition state, leading to the simultaneous removal of the leaving group and proton.

Zaitsev's Rule

Zaitsev's Rule states that in elimination reactions, the more substituted alkene is generally the major product. This is due to the stability of alkenes; more substituted alkenes have greater hyperconjugation and lower energy, making them more favorable in terms of yield compared to less substituted alkenes.

Regioselectivity in Elimination Reactions

Regioselectivity refers to the preference of a chemical reaction to yield one structural isomer over others. In E2 reactions, the orientation of the leaving group and the hydrogen being abstracted can lead to different alkene products, and understanding the sterics and electronics of the substrate can help predict which product will be favored.

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Related Practice

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

Draw the elimination products for each of the following E2 reactions; if the products can exist as stereoisomers, indicate which stereoisomers are obtained.

c. (2R,3S)-2-chloro-3-methylpentane + high concentration of CH₃O^-

Textbook Question

When 2-bromo-2,3-dimethylbutane reacts with a strong base, two alkenes (2,3-dimethyl-1-butene and 2,3-dimethyl-2-butene) are formed.

a. Which of the bases (A, B, C, or D) would form the highest percentage of the 1-alkene?

b. Which would give the highest percentage of the 2-alkene?

Textbook Question

What is the major elimination product obtained from the 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 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:

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Two elimination products are obtained from the following E2 reaction: a. What are the elimination products? b. Which is formed in greater yield?

Key Concepts

E2 Reaction Mechanism

Zaitsev's Rule

Regioselectivity in Elimination Reactions

Watch next

Two elimination products are obtained from the following E2 reaction:

a. What are the elimination products?
b. Which is formed in greater yield?