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)

Previous problemNext problem

3:19 minutes

Problem 50d

Textbook Question

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

Verified step by step guidance

Step 1: Analyze the structure of the alkyl halide (benzyl bromide) in both reactions. Benzyl bromide contains a benzylic carbon, which is adjacent to the benzene ring. This benzylic position is highly reactive due to resonance stabilization of the carbocation formed during substitution or elimination.

Step 2: Examine the base used in each reaction. In the first reaction, LiNH₂ is a strong, small base. Small bases typically favor elimination (E2 mechanism) because they can easily abstract a proton from the β-carbon. In the second reaction, the base is a bulky amine (lithium diisopropylamide, LDA). Bulky bases strongly favor elimination over substitution because steric hindrance prevents them from effectively attacking the electrophilic carbon in substitution reactions.

Step 3: Consider the solvent (THF) used in both reactions. THF is an aprotic solvent, which generally supports elimination reactions, especially when strong bases are involved. Aprotic solvents do not stabilize carbocations as well as protic solvents, making substitution less favorable.

Step 4: Compare the steric effects of the bases. The bulky base (LDA) in the second reaction will strongly favor elimination because it is sterically hindered and cannot easily approach the electrophilic carbon for substitution. The smaller base (LiNH₂) in the first reaction may allow for some substitution, but elimination is still likely to be favored due to the strength of the base.

Step 5: Conclude that elimination is more favored in the reaction with the bulky base (LDA) compared to the reaction with the smaller base (LiNH₂). The steric hindrance of LDA and the use of an aprotic solvent make elimination the dominant pathway in the second reaction.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

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

Elimination vs. Substitution Reactions

In organic chemistry, elimination reactions involve the removal of atoms or groups from a molecule, resulting in the formation of a double bond or a ring structure. In contrast, substitution reactions involve replacing one atom or group with another. The preference for elimination over substitution often depends on factors such as the structure of the substrate, the nature of the leaving group, and the reaction conditions.

Regioselectivity in Reactions

Regioselectivity refers to the preference of a chemical reaction to occur at one location over another in a molecule. In the context of elimination and substitution reactions, the regioselectivity can influence whether a reaction will favor the formation of a double bond or the substitution of a functional group. Understanding the regioselectivity helps predict the major products formed in a reaction.

Role of Solvents in Organic Reactions

The choice of solvent can significantly affect the outcome of organic reactions. Polar protic solvents tend to stabilize ions and can favor substitution reactions, while polar aprotic solvents can promote elimination reactions by stabilizing the transition state. In the given question, the use of THF (tetrahydrofuran) as a solvent may influence whether elimination or substitution is favored in the reactions depicted.

Watch next

Master Overview of the flowchart. with a bite sized video explanation from Johnny

Start learning

Related Videos

Related Practice

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?

(a)

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

Textbook Question

What are the products of the following reactions?

Show more practices