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

Nucleophiles and Basicity

Organic Chemistry

8. Elimination Reactions

Nucleophiles and Basicity

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3:53 minutes

Problem 16a,b

Textbook Question

For each pair, predict the stronger nucleophile in the SN2 reaction (using an alcohol as the solvent). Explain your prediction.
a. (CH₃CH₂)₃N or (CH₃CH₂)₂NH
b. (CH₃)₂O or (CH₃)₂S

Verified step by step guidance

Step 1: Understand the concept of nucleophilicity in SN2 reactions. Nucleophilicity refers to the ability of a species to donate a pair of electrons to an electrophile. In SN2 reactions, nucleophilicity is influenced by factors such as charge, electronegativity, steric hindrance, and the solvent used.

Step 2: Analyze the solvent's role. Alcohol is a protic solvent, meaning it can form hydrogen bonds with nucleophiles. Protic solvents tend to stabilize charged nucleophiles through hydrogen bonding, which can reduce their nucleophilicity. Neutral nucleophiles are less affected by this stabilization.

Step 3: Compare the nucleophiles in part (a). (CH3CH2)3N is a tertiary amine, while (CH3CH2)2NH is a secondary amine. Tertiary amines are more sterically hindered, making it harder for them to approach the electrophile in an SN2 reaction. Secondary amines, with less steric hindrance, are typically stronger nucleophiles in SN2 reactions.

Step 4: Compare the nucleophiles in part (b). (CH3)2O is an ether, while (CH3)2S is a thioether. Sulfur is less electronegative than oxygen, meaning it holds onto its electrons less tightly and is more polarizable. This makes (CH3)2S a stronger nucleophile than (CH3)2O in an SN2 reaction, especially in a protic solvent like alcohol.

Step 5: Summarize the predictions. For part (a), (CH3CH2)2NH is the stronger nucleophile due to reduced steric hindrance. For part (b), (CH3)2S is the stronger nucleophile due to sulfur's lower electronegativity and higher polarizability compared to oxygen.

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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 during a chemical reaction. Stronger nucleophiles are typically negatively charged or have lone pairs that can be readily donated. Factors influencing nucleophilicity include charge, electronegativity, and steric hindrance, with less steric hindrance generally leading to stronger nucleophiles.

SN2 Mechanism

The SN2 mechanism is a type of nucleophilic substitution reaction where the nucleophile attacks the electrophile from the opposite side of the leaving group, resulting in a concerted reaction. This mechanism is characterized by a single transition state and is sensitive to steric factors; less hindered substrates favor SN2 reactions, making the choice of nucleophile and solvent critical for predicting reaction outcomes.

Solvent Effects

The choice of solvent can significantly influence nucleophilicity and reaction rates in SN2 reactions. Protic solvents, like alcohols, can stabilize nucleophiles through hydrogen bonding, potentially reducing their reactivity. In contrast, aprotic solvents can enhance nucleophilicity by not stabilizing the nucleophile as much, thus affecting the overall reaction dynamics and the strength of the nucleophiles involved.