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)

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7:02 minutes

Problem 43b

Textbook Question

Suggest an appropriate base to synthesize the alkene as the major product from the starting haloalkane.
(b)

Verified step by step guidance

Analyze the starting material: The haloalkane provided is a tertiary alkyl bromide. This structure is prone to elimination reactions due to steric hindrance, favoring the E2 mechanism over substitution.

Understand the desired product: The target molecule is an alkene, specifically the more substituted alkene, which is typically the major product due to Zaitsev's rule. Zaitsev's rule states that elimination reactions favor the formation of the more stable, highly substituted alkene.

Choose an appropriate base: To favor the E2 elimination mechanism, a strong base is required. Bulky bases like potassium tert-butoxide (KOtBu) are often used to ensure elimination rather than substitution. Additionally, bulky bases can help avoid steric hindrance and promote the formation of the desired alkene.

Consider the reaction conditions: The reaction should be carried out in a polar aprotic solvent, such as dimethyl sulfoxide (DMSO) or acetone, to facilitate the E2 mechanism. Heat is often applied to further favor elimination over substitution.

Verify the regioselectivity: Using a bulky base ensures that the elimination occurs preferentially at the β-hydrogen that leads to the formation of the more substituted alkene, consistent with Zaitsev's rule.

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Key Concepts

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

Elimination Reactions

Elimination reactions involve the removal of a leaving group and a hydrogen atom from adjacent carbon atoms, resulting in the formation of a double bond. In organic chemistry, these reactions are crucial for synthesizing alkenes from haloalkanes. The most common types are E1 and E2 mechanisms, which differ in their reaction pathways and conditions.

Base Selection

The choice of base is critical in elimination reactions, as it influences the reaction mechanism and the major product formed. Strong bases, such as sodium ethoxide or potassium tert-butoxide, favor E2 mechanisms, leading to the formation of alkenes. The sterics and electronics of the base can also affect regioselectivity and the stability of the resulting alkene.

Regioselectivity

Regioselectivity refers to the preference of a chemical reaction to yield one structural isomer over others. In elimination reactions, this concept is important when determining which alkene product is favored. The Zaitsev's rule states that the more substituted alkene is typically the major product, while the Hofmann rule applies when sterically hindered bases are used, leading to less substituted alkenes.

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