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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1:30 minutes

Problem 33a

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

Verified step by step guidance

Step 1: Recognize the type of reaction. The reaction involves 1-bromohexane (a primary alkyl halide) and sodium ethoxide (a strong base and nucleophile) in ethanol (a polar protic solvent). This setup suggests that both substitution (S_N2) and elimination (E2) mechanisms are possible.

Step 2: Analyze the substrate. 1-Bromohexane is a primary alkyl halide, which favors the S_N2 mechanism because primary carbons are less sterically hindered, allowing the nucleophile to attack more easily. However, the presence of a strong base like sodium ethoxide also makes elimination (E2) a competing pathway.

Step 3: Consider the nucleophile and solvent. Sodium ethoxide is both a strong nucleophile and a strong base. Ethanol, being a polar protic solvent, can stabilize the transition state for elimination (E2) but may also allow for substitution (S_N2) to occur. The balance between these pathways depends on the reaction conditions.

Step 4: Predict the products. For the S_N2 pathway, the nucleophile (ethoxide ion) will attack the carbon bonded to the bromine atom, displacing the bromide ion and forming ethoxyhexane. For the E2 pathway, the ethoxide ion will abstract a β-hydrogen (from a carbon adjacent to the carbon bonded to bromine), leading to the formation of 1-hexene as the elimination product.

Step 5: Determine the most likely mechanism. Since 1-bromohexane is a primary alkyl halide, the S_N2 mechanism is likely to dominate under these conditions. However, the strong base (sodium ethoxide) and polar protic solvent also make elimination (E2) a viable pathway, especially at higher temperatures. The reaction may yield a mixture of products, with the substitution product (ethoxyhexane) being the major product and the elimination product (1-hexene) being the minor product.

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Key Concepts

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

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group in a molecule by a nucleophile. In this case, sodium ethoxide acts as a nucleophile that can attack the carbon atom bonded to the bromine in 1-bromohexane. Understanding the mechanisms, such as SN1 and SN2, is crucial for predicting the products formed in this reaction.

SN2 Mechanism

The SN2 mechanism is a one-step process where the nucleophile attacks the electrophile from the opposite side of the leaving group, resulting in a concerted reaction. This mechanism is favored for primary alkyl halides like 1-bromohexane due to less steric hindrance, leading to the formation of hexane and sodium bromide as products.

Solvent Effects on Reaction Mechanisms

The choice of solvent can significantly influence the reaction mechanism. Ethanol, being a polar protic solvent, can stabilize the transition state and the leaving group, potentially favoring the SN1 mechanism. However, in this case, the primary nature of 1-bromohexane and the strong nucleophile (sodium ethoxide) suggest that the SN2 pathway is more likely to dominate.

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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 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)

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.

Textbook Question

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

(d)

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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

Key Concepts

Nucleophilic Substitution Reactions

SN2 Mechanism

Solvent Effects on Reaction Mechanisms

Watch next

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