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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6:02 minutes

Problem 33b

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

Verified step by step guidance

Step 1: Identify the type of reaction. The reaction involves 2-chlorohexane (a secondary alkyl halide) and sodium methoxide (NaOCH3) in methanol. Sodium methoxide is a strong base and a good nucleophile, so this reaction can proceed via either an E2 (elimination) or SN2 (substitution) mechanism. The solvent, methanol, is polar protic, which can influence the mechanism.

Step 2: Analyze the substrate. 2-chlorohexane is a secondary alkyl halide. Secondary alkyl halides can undergo both SN2 and E2 reactions, but the strong base (NaOCH3) favors the E2 mechanism over SN2. Additionally, steric hindrance around the secondary carbon makes SN2 less favorable.

Step 3: Predict the E2 elimination product. In an E2 reaction, the base (methoxide ion) abstracts a β-hydrogen (a hydrogen atom on a carbon adjacent to the carbon bearing the leaving group). The leaving group (Cl⁻) departs simultaneously, forming a double bond. Identify all β-hydrogens and determine the possible alkenes that can form. Consider Zaitsev's rule, which states that the more substituted alkene is generally the major product.

Step 4: Consider the possibility of SN2 substitution. Although less likely due to steric hindrance and the strong base favoring elimination, substitution could occur if the methoxide ion attacks the carbon bearing the leaving group (Cl). This would result in the replacement of the chlorine atom with a methoxy group (-OCH3). However, this pathway is less favored under these conditions.

Step 5: Conclude the most likely products and mechanisms. The major product is expected to result from the E2 elimination mechanism, with the formation of the more substituted alkene (following Zaitsev's rule). The SN2 substitution product (2-methoxyhexane) is a minor product due to steric hindrance and the reaction conditions favoring elimination.

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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, NaOCH3 acts as a nucleophile, attacking the carbon atom bonded to the chlorine in 2-chlorohexane. Understanding the mechanism (either SN1 or SN2) is crucial for predicting the products formed.

SN1 vs. SN2 Mechanisms

The SN1 mechanism is a two-step process where the leaving group departs first, forming a carbocation intermediate, followed by nucleophilic attack. In contrast, the SN2 mechanism is a one-step process where the nucleophile attacks the substrate simultaneously as the leaving group departs. The structure of 2-chlorohexane and the solvent (methanol) influence which mechanism is favored.

Solvent Effects on Reaction Mechanisms

The choice of solvent can significantly affect the reaction pathway. Methanol, a polar protic solvent, stabilizes carbocations and can facilitate SN1 reactions. However, it can also solvate nucleophiles, impacting the rate of SN2 reactions. Understanding these solvent effects is essential for predicting the most likely products in the reaction.

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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.

a. 1−bromohexane + sodium ethoxide in ethanol

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)

Textbook Question

Propose mechanisms for the following reactions. Additional products may be formed, but your mechanism only needs to explain the products shown.

(c)

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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.b. 2−chlorohexane + NaOCH3 in methanol

Key Concepts

Nucleophilic Substitution Reactions

SN1 vs. SN2 Mechanisms

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.
b. 2−chlorohexane + NaOCH₃ in methanol