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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1:12 minutes

Problem 46a

Textbook Question

Provide a mechanism for the following E1 reactions.
(a)

Verified step by step guidance

Identify the substrate: In an E1 reaction, the substrate is typically a secondary or tertiary alkyl halide or alcohol. Determine the structure of the starting material to understand the reaction pathway.

Protonation or leaving group departure: If the substrate is an alcohol, protonate the hydroxyl group to convert it into a better leaving group (water). If the substrate already contains a good leaving group (e.g., a halide), this step is not necessary. The leaving group departs, forming a carbocation intermediate.

Carbocation stability: Analyze the carbocation intermediate formed after the leaving group departs. If possible, check for carbocation rearrangements (e.g., hydride or alkyl shifts) to form a more stable carbocation.

Beta-hydrogen elimination: Identify a beta-hydrogen (a hydrogen atom on a carbon adjacent to the carbocation). A base (often the solvent or a weak base) abstracts the beta-hydrogen, and the electrons from the C-H bond form a π-bond, resulting in the formation of the alkene product.

Determine the major product: Use Zaitsev's rule to predict the major product. The more substituted alkene (the one with more alkyl groups attached to the double bond) is typically favored in E1 reactions.

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Key Concepts

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

E1 Mechanism

The E1 mechanism, or unimolecular elimination, involves two main steps: the formation of a carbocation intermediate followed by the loss of a leaving group to form a double bond. This process typically occurs in polar protic solvents and is favored by tertiary substrates due to their ability to stabilize the carbocation. Understanding the E1 mechanism is crucial for predicting the products of elimination reactions.

Carbocation Stability

Carbocation stability is a key factor in E1 reactions, as the rate-determining step involves the formation of a carbocation. Tertiary carbocations are more stable than secondary or primary ones due to hyperconjugation and inductive effects from surrounding alkyl groups. Recognizing the stability of different carbocations helps in predicting the likelihood of E1 reactions occurring with specific substrates.

Leaving Groups

The quality of the leaving group significantly influences the rate of E1 reactions. Good leaving groups, such as halides or tosylates, can stabilize the transition state and facilitate the formation of the carbocation. Understanding which groups can effectively leave is essential for determining the feasibility of an E1 reaction and predicting the products formed.

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