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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8:07 minutes

Problem 22a

Textbook Question

When (1-bromoethyl)cyclohexane is heated in methanol for an extended period of time, five products result: two ethers and three alkenes. Predict the products of this reaction, and propose mechanisms for their formation.

Verified step by step guidance

Step 1: Recognize the reaction conditions. Heating (1-bromoethyl)cyclohexane in methanol suggests a solvolysis reaction, where methanol acts as both the solvent and nucleophile. This indicates that the reaction likely proceeds via an SN1/E1 mechanism due to the polar protic solvent and the secondary alkyl halide.

Step 2: Propose the first step of the mechanism. The bromine atom in (1-bromoethyl)cyclohexane is a good leaving group. Under heat, the C-Br bond breaks heterolytically, forming a secondary carbocation intermediate on the cyclohexane ring. This carbocation is stabilized by hyperconjugation and inductive effects.

Step 3: Predict the formation of ethers. Methanol, acting as a nucleophile, can attack the carbocation to form an ether product. Since methanol can attack from either side of the planar carbocation, two stereoisomeric ethers (R and S configurations) are formed.

Step 4: Predict the formation of alkenes. The carbocation can also undergo elimination (E1 mechanism). A proton from a β-carbon (adjacent to the carbocation) is removed by methanol acting as a base, leading to the formation of alkenes. Three possible alkenes can form due to different β-hydrogens being eliminated, including cis/trans isomers if applicable.

Step 5: Summarize the products. The reaction yields two ethers (stereoisomers) and three alkenes (including possible cis/trans isomers). The mechanisms involve both substitution (SN1) and elimination (E1) pathways, with methanol playing dual roles as a nucleophile and base.

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Key Concepts

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

Nucleophilic Substitution

Nucleophilic substitution is a fundamental reaction in organic chemistry where a nucleophile attacks an electrophile, replacing a leaving group. In the case of (1-bromoethyl)cyclohexane reacting with methanol, methanol acts as a nucleophile, leading to the formation of ethers through an SN1 or SN2 mechanism, depending on the reaction conditions.

Elimination Reactions

Elimination reactions involve the removal of a small molecule from a larger one, typically resulting in the formation of alkenes. In this scenario, heating (1-bromoethyl)cyclohexane can promote elimination, where the bromine atom is lost along with a hydrogen atom from an adjacent carbon, leading to the formation of alkenes through either E1 or E2 mechanisms.

Reaction Mechanisms

Understanding reaction mechanisms is crucial for predicting the products of organic reactions. Mechanisms describe the step-by-step process of how reactants transform into products, including the intermediates formed. In this case, both nucleophilic substitution and elimination pathways must be considered to explain the formation of the observed ethers and alkenes.

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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.

g. 1−bromo−1−methylcyclopentane + NaOEt in ethanol

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.

(a)

Textbook Question

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

a. 1−bromo−1−methylcyclohexane + NaOH in acetone

Textbook Question

Under second-order conditions (strong base/nucleophile), S_N2 and E2 reactions may occur simultaneously and compete with each other. Show what products might be expected from the reaction of 2-bromo-3-methylbutane (a moderately hindered 2° alkyl halide) with sodium ethoxide.

Textbook Question

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

a. 3-bromo-3-ethylpentane heated in methanol

Textbook Question

Write a balanced equation for each reaction, showing the major product you expect.

(b)

Textbook Question

If 2-fluoropentane could undergo an E1 reaction, would you expect the major product to be the more stable alkene or the less stable alkene? Explain your answer.

Textbook Question

Four alkenes are formed from the E1 reaction of 3-bromo-2,3-dimethylpentane and methanol. Draw the structures of the alkenes and rank them according to the amount that would be formed.

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