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

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2:50 minutes

Problem 58

Textbook Question

Would you expect acetate ion (CH₃CO₂⁻) to be a better nucleophile in an S_N2 reaction with an alkyl halide carried out in methanol or in dimethyl sulfoxide?

Verified step by step guidance

Understand the role of the solvent in an SN2 reaction: In an SN2 reaction, the nucleophile attacks the electrophilic carbon of the alkyl halide in a single concerted step. The solvent can significantly influence the nucleophilicity of the nucleophile. Polar aprotic solvents enhance nucleophilicity, while polar protic solvents can hinder it by stabilizing the nucleophile through hydrogen bonding.

Analyze the solvents given: Methanol (CH3OH) is a polar protic solvent, meaning it has hydrogen atoms capable of forming hydrogen bonds with the nucleophile. Dimethyl sulfoxide (DMSO, (CH3)2SO) is a polar aprotic solvent, meaning it does not have hydrogen atoms that can form hydrogen bonds, but it can stabilize cations without significantly stabilizing the nucleophile.

Consider the acetate ion (CH3CO2−): The acetate ion is a negatively charged nucleophile. In a polar protic solvent like methanol, the acetate ion will be stabilized by hydrogen bonding, reducing its nucleophilicity. In contrast, in a polar aprotic solvent like DMSO, the acetate ion will not be stabilized by hydrogen bonding, allowing it to remain more reactive as a nucleophile.

Relate solvent effects to the SN2 reaction: Since SN2 reactions are favored by strong nucleophiles, the acetate ion will be a better nucleophile in DMSO (polar aprotic solvent) compared to methanol (polar protic solvent). This is because DMSO does not hinder the nucleophile's reactivity, whereas methanol does.

Conclude the comparison: Based on the solvent effects, the acetate ion (CH3CO2−) would be a better nucleophile in an SN2 reaction with an alkyl halide when the reaction is carried out in dimethyl sulfoxide (DMSO) rather than in methanol.

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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 species to donate an electron pair to an electrophile, forming a chemical bond. It is influenced by factors such as charge, electronegativity, and solvent effects. In general, negatively charged species like acetate ion are stronger nucleophiles than their neutral counterparts. Understanding nucleophilicity is crucial for predicting the outcome of nucleophilic substitution reactions.

Solvent Effects

The choice of solvent can significantly impact the rate and mechanism of nucleophilic substitution reactions. Polar protic solvents, like methanol, can stabilize ions through hydrogen bonding, potentially reducing nucleophilicity. In contrast, polar aprotic solvents, such as dimethyl sulfoxide (DMSO), do not stabilize anions as effectively, often leading to increased nucleophilicity. Recognizing how solvents influence reaction dynamics is essential for evaluating reaction conditions.

SN2 Mechanism

The SN2 mechanism is a type of nucleophilic substitution reaction characterized by a single concerted step where the nucleophile attacks the electrophile, leading to the displacement of a leaving group. This mechanism is bimolecular, meaning the rate depends on the concentration of both the nucleophile and the substrate. Understanding the SN2 mechanism is vital for predicting reaction pathways and outcomes in organic chemistry.

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Would you expect acetate ion (CH3CO2−) to be a better nucleophile in an SN2 reaction with an alkyl halide carried out in methanol or in dimethyl sulfoxide?

Key Concepts

Nucleophilicity

Solvent Effects

S<sub>N</sub>2 Mechanism

Watch next

Would you expect acetate ion (CH₃CO₂⁻) to be a better nucleophile in an S_N2 reaction with an alkyl halide carried out in methanol or in dimethyl sulfoxide?