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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6:26 minutes

Problem 32b

Textbook Question

Predict the major and minor elimination products of the following proposed reactions (ignoring any possible substitutions for now). In each case, explain whether you expect the mechanism of the elimination to be E1 or E2.
(b)

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Step 1: Analyze the reaction conditions. The presence of AgNO3 in CH3OH (methanol) and heat suggests that the reaction is likely to proceed via an E1 elimination mechanism. AgNO3 helps to remove the bromide ion (Br⁻), forming a carbocation intermediate, which is characteristic of E1 mechanisms.

Step 2: Identify the substrate. The substrate is a cyclopentyl bromide with a methyl group attached to the carbon bearing the bromine atom. This structure allows for the formation of a secondary carbocation upon loss of the bromide ion.

Step 3: Predict the carbocation stability. The secondary carbocation formed after the bromide leaves is relatively stable. Additionally, the methyl group can provide hyperconjugation and inductive effects, further stabilizing the carbocation.

Step 4: Determine the possible elimination products. In an E1 mechanism, elimination occurs by removing a β-hydrogen from a carbon adjacent to the carbocation. This can lead to the formation of alkenes. The major product will likely be the more substituted alkene (Zaitsev's rule), while the minor product will be the less substituted alkene.

Step 5: Consider stereochemistry and regioselectivity. The major product will be the alkene with the double bond between the cyclopentyl ring and the methyl group (more substituted), while the minor product will have the double bond between the cyclopentyl ring and the less substituted β-carbon. No stereospecificity is expected in E1 mechanisms.

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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. The two main types are E1 and E2 mechanisms. E1 is a two-step process where the leaving group departs first, forming a carbocation, followed by deprotonation. E2 is a one-step concerted process where the base removes a proton while the leaving group exits simultaneously.

E1 vs. E2 Mechanisms

The E1 mechanism is favored in polar protic solvents and with substrates that can stabilize carbocations, such as tertiary halides. In contrast, the E2 mechanism requires a strong base and is favored in polar aprotic solvents, typically involving primary or secondary substrates. The choice between E1 and E2 can significantly affect the product distribution and reaction rate.

Regioselectivity in Elimination

Regioselectivity refers to the preference for the formation of one constitutional isomer over others in a chemical reaction. In elimination reactions, this often results in the formation of more stable alkenes, such as the Zaitsev product, which is the more substituted alkene, or the Hofmann product, which is the less substituted alkene. Understanding regioselectivity is crucial for predicting the major and minor products of elimination reactions.

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Related Practice

Textbook Question

Predict the products and mechanisms of the following reactions. When more than one product or mechanism is possible, explain which are most likely.

e. isobutyliodide + KOH in ethanol/water

f. isobutylchloride + AgNO₃ in ethanol/water

Textbook Question

The solvolysis of 2-bromo-3-methylbutane potentially can give several products, including both E1 and products from both the unrearranged carbocation and the rearranged carbocation. Mechanisms 6-6 and 7-2 show the products from the rearranged carbocation. Summarize all the possible products, showing which carbocation they come from and whether they are the products of E1 or reactions.

Textbook Question

For each reaction, decide whether substitution or elimination (or both) is possible, and predict the products you expect. Label the major products.

b. 1-bromo-1-methylcyclohexane + triethylamine(Et₃N:)

Textbook Question

Give the substitution and elimination products you would expect from the following reactions.

b. 1-iodo-1-phenylcyclopentane heated in ethanol

Textbook Question

Predict the products and mechanisms of the following reactions. When more than one product or mechanism is possible, explain which are most likely.

a. 1−bromohexane + sodium ethoxide in ethanol

Textbook Question

Predict the products and mechanisms of the following reactions. When more than one product or mechanism is possible, explain which are most likely.

b. 2−chlorohexane + NaOCH₃ in methanol

Textbook Question

When (±)−2,3−dibromobutane reacts with potassium hydroxide, some of the products are (2S,3R)-3-bromobutan-2-ol and its enantiomer and trans-2-bromobut-2-ene. Give mechanisms to account for these products.

Textbook Question

Make models of the following compounds, and predict the products formed when they react with the strong bases shown.

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Predict the major and minor elimination products of the following proposed reactions (ignoring any possible substitutions for now). In each case, explain whether you expect the mechanism of the elimination to be E1 or E2.(b)

Key Concepts

Elimination Reactions

E1 vs. E2 Mechanisms

Regioselectivity in Elimination

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Predict the major and minor elimination products of the following proposed reactions (ignoring any possible substitutions for now). In each case, explain whether you expect the mechanism of the elimination to be E1 or E2.
(b)