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

7. Substitution Reactions

SN2 Reaction

Organic Chemistry

7. Substitution Reactions

SN2 Reaction

Previous problemNext problem

7:58 minutes

Problem 108c

Textbook Question

The rate of the reaction of methyl iodide with quinuclidine was measured in nitrobenzene, and then the rate of the reaction of methyl iodide with triethylamine was measured in the same solvent. The concentration of the reagents was the same in both experiments.
c. Which alkyl halide has the larger k_quinuclidine/k_{triethylamine} ratio?

Verified step by step guidance

Step 1: Analyze the chemical structures provided in the image. Quinuclidine (1-azabicyclo[2.2.1]hepta-2,5-diene) is a bicyclic amine with a rigid structure and a highly nucleophilic nitrogen atom. Triisobutylamine is a tertiary amine with bulky isobutyl groups surrounding the nitrogen atom, which can hinder its nucleophilicity due to steric effects.

Step 2: Consider the reaction mechanism. The reaction of methyl iodide with amines typically proceeds via an SN2 mechanism, where the nucleophile attacks the electrophilic carbon of the methyl iodide, displacing the iodide ion. The rate of the reaction depends on the nucleophilicity of the amine and steric hindrance around the nucleophilic site.

Step 3: Compare the nucleophilicity of quinuclidine and triisobutylamine. Quinuclidine has a highly accessible nitrogen atom due to its rigid structure, making it a stronger nucleophile. In contrast, triisobutylamine has bulky substituents that create steric hindrance, reducing its ability to act as a nucleophile.

Step 4: Evaluate the kquinuclidine/ktriethylamine ratio. Since quinuclidine is more nucleophilic and less sterically hindered, it is expected to react faster with methyl iodide compared to triisobutylamine. This would result in a larger kquinuclidine/ktriethylamine ratio.

Step 5: Conclude that the alkyl halide (methyl iodide) will exhibit a larger kquinuclidine/ktriethylamine ratio when reacting with quinuclidine compared to triisobutylamine, due to the differences in nucleophilicity and steric hindrance between the two amines.

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.

Nucleophilicity

Nucleophilicity refers to the ability of a nucleophile to donate an electron pair to an electrophile, such as an alkyl halide. In this context, quinuclidine is a stronger nucleophile than triethylamine due to its more basic nature and the presence of a nitrogen atom in a bicyclic structure, which can stabilize the negative charge better during the reaction.

Reaction Rate Constants (k)

The rate constant (k) is a proportionality factor in the rate law of a chemical reaction, indicating how quickly a reaction occurs. The ratio of k values for different nucleophiles, such as kquinuclidine and ktriethylamine, provides insight into their relative reactivity. A higher ratio suggests that the reaction with quinuclidine proceeds faster than with triethylamine under the same conditions.

Solvent Effects

The choice of solvent can significantly influence the rate of a reaction by stabilizing reactants, intermediates, or transition states. Nitrobenzene, a polar aprotic solvent, can enhance the nucleophilicity of quinuclidine while having a different effect on triethylamine. Understanding how solvents interact with reactants is crucial for predicting reaction outcomes and comparing reaction rates.

Watch next

Master Drawing the SN2 Mechanism with a bite sized video explanation from Johnny

Start learning

Related Videos

Related Practice

Textbook Question

Starting with an alkyl halide, how could the following compounds be prepared?

a. 2-methoxybutane

Textbook Question

Starting with an alkyl halide, how could the following compounds be prepared?

b. 1-methoxybutane

Textbook Question

2-Acetoxycyclohexyl tosylate reacts with acetate ion to form 1,2-cyclohexanediol diacetate. The reaction is stereospecific—that is, the stereoisomers obtained as products depend on the stereoisomer used as a reactant. Recall that because 2-acetoxycyclohexyl tosylate has two asymmetric centers, it has four stereoisomers—two are cis and two are trans. Explain the following observations:

b. Both trans reactants form the same racemic mixture.

Textbook Question

The rate of the reaction of methyl iodide with quinuclidine was measured in nitrobenzene, and then the rate of the reaction of methyl iodide with triethylamine was measured in the same solvent. The concentration of the reagents was the same in both experiments.

b. The same experiment was done using isopropyl iodide instead of methyl iodide. Which reaction had the larger rate constant?

Textbook Question

Starting with an alkyl halide, how could the following compounds be prepared?

c. butylmethylamine

Textbook Question

The reaction of an amine with an alkyl halide gives an ammonium salt.R3N amine + R'—X alkyl halide —> R3(N+)—R' X- ammonium salt The rate of this SN2 reaction is sensitive to the polarity of the solvent. 1. Draw an energy diagram for this reaction in a nonpolar solvent and another in a polar solvent. 2. Consider the nature of the transition state, and explain why this reaction should be sensitive to the polarity of the solvent. 3. Predict whether it will be faster or slower in a more polar solvent.

Textbook Question

Under certain conditions, the reaction of 0.5 M 1-bromobutane with 1.0 M sodium methoxide forms 1-methoxybutane at a rate of 0.05 mol/L per second.

c. Show another S_N2 reaction using a different combination of an alkoxide and an alkyl bromide that also produces 1-methoxybutane.

Show more practices

Download the Mobile app

Privacy

Do not sell my personal information

Accessibility

Patent notice

Sitemap