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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4:09 minutes

Problem 50a

Textbook Question

For which of the following reactions would you expect elimination to be more favored than substitution?
(a)

Verified step by step guidance

Step 1: Analyze the reaction conditions for both cases. In the first reaction, NaOEt (sodium ethoxide) in EtOH (ethanol) is used, which is a small, strong base. In the second reaction, NaOt-Bu (sodium tert-butoxide) in t-BuOH (tert-butanol) is used, which is a bulky, strong base.

Step 2: Understand the role of the base size in determining the reaction pathway. Small bases like NaOEt can easily approach the electrophilic carbon and favor substitution (S_N2 mechanism). Bulky bases like NaOt-Bu, due to steric hindrance, are less likely to approach the electrophilic carbon and instead favor elimination (E2 mechanism).

Step 3: Consider the structure of the alkyl halide. Both alkyl halides are secondary bromides, which can undergo both substitution and elimination. However, the steric hindrance around the electrophilic carbon plays a role in determining the favored pathway.

Step 4: Evaluate the solvent effects. Ethanol (EtOH) is a protic solvent that can stabilize the transition state for substitution reactions. Tert-butanol (t-BuOH), being bulky, does not stabilize substitution as effectively and further promotes elimination.

Step 5: Conclude that elimination is more favored in the second reaction (NaOt-Bu/t-BuOH) due to the bulky base and solvent, while substitution is more competitive in the first reaction (NaOEt/EtOH) due to the smaller base and solvent effects.

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Key Concepts

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

Elimination vs. Substitution Reactions

Elimination reactions involve the removal of a leaving group and a hydrogen atom, resulting in the formation of a double bond, while substitution reactions replace a leaving group with a nucleophile. The preference for one mechanism over the other depends on factors such as the structure of the substrate, the strength of the nucleophile/base, and the reaction conditions.

Zaitsev's Rule

Zaitsev's Rule states that in elimination reactions, the more substituted alkene is typically the major product. This is due to the stability of more substituted alkenes, which are favored thermodynamically. Understanding this rule helps predict the outcome of elimination reactions, especially when considering steric hindrance and the nature of the base used.

Sterics and Base Strength

The steric hindrance of the base and the substrate plays a crucial role in determining whether elimination or substitution will be favored. Bulky bases, like t-BuOK, tend to favor elimination due to their inability to effectively approach the substrate for substitution. Conversely, smaller bases can facilitate substitution reactions more readily, highlighting the importance of base choice in reaction pathways.

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Related Practice

Textbook Question

For each pair, choose the haloalkane that would react most quickly in an S_N1 or E1 reaction.

(a)

Textbook Question

Predict the product(s) that would result when the following molecules are allowed to react under the following conditions: (v) H₂O; (vi) NaOH, H₂O. If there is no reaction, write 'no reaction.'

(f)

Textbook Question

Identify whether each of the following reactions proceed by an S_N1, S_N2, E1, or E2 mechanism.

(c)

Textbook Question

Identify whether each of the following reactions proceed by an S_N1, S_N2, E1, or E2 mechanism.

(b)

Textbook Question

For which of the following reactions would you expect elimination to be more favored than substitution?

(d)

Textbook Question

When the following compound undergoes solvolysis in ethanol, three products are obtained. Propose a mechanism to account for the formation of these products.

Textbook Question

Draw the substitution and elimination products for the following reactions, showing the configuration of each product:

c. 1-chloro-1-methylcyclohexane + CH₃O⁻

d. 1-chloro-1-methylcyclohexane + CH₃OH

Textbook Question

For each of the following reactions, draw the major elimination product; if the product can exist as stereoisomers, indicate which stereoisomer is obtained in greater yield.

a. (R)-2-bromohexane + high concentration of CH₃O⁻

b. (R)-3-bromo-3-methylhexane + CH₃OH

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For which of the following reactions would you expect elimination to be more favored than substitution?(a)

Key Concepts

Elimination vs. Substitution Reactions

Zaitsev's Rule

Sterics and Base Strength

Watch next

For which of the following reactions would you expect elimination to be more favored than substitution?
(a)