Question

For each pair, predict the stronger nucleophile in the SN2 reaction (using an alcohol as the solvent). Explain your prediction.g. (CH3)2CHO– or CH3CH2CH2O–h. I– or Cl–

Accepted Answer

Step 1: Understand the SN2 reaction mechanism. In an SN2 reaction, the nucleophile attacks the electrophilic carbon in a single concerted step, displacing the leaving group. The strength of the nucleophile plays a critical role in determining the reaction rate. Step 2: Analyze the nucleophiles in part (g): (CH3)2CHO⁻ (a secondary alkoxide) and CH3CH2CH2O⁻ (a primary alkoxide). In general, primary alkoxides are less sterically hindered than secondary alkoxides, making them stronger nucleophiles in SN2 reactions. Additionally, both nucleophiles are negatively charged, so steric hindrance is the key factor here. Step 3: Analyze the nucleophiles in part (h): I⁻ and Cl⁻. In polar protic solvents like alcohols, larger anions are better nucleophiles because they are less solvated and can attack the electrophile more effectively. I⁻ is larger than Cl⁻, so it is the stronger nucleophile in this case. Step 4: Consider the solvent effect. Alcohols are polar protic solvents, which stabilize smaller, more electronegative anions (like Cl⁻) through hydrogen bonding. This stabilization reduces their nucleophilicity compared to larger anions (like I⁻). Similarly, steric hindrance in alkoxides is exacerbated in polar protic solvents, further favoring less hindered nucleophiles. Step 5: Summarize the predictions. For part (g), CH3CH2CH2O⁻ is the stronger nucleophile due to less steric hindrance. For part (h), I⁻ is the stronger nucleophile because it is larger and less solvated in the polar protic solvent.

For each pair, predict the stronger nucleophile in the SN2 reaction (using an alcohol as the solvent). Explain your prediction.
g. (CH₃)₂CHO^– or CH₃CH₂CH₂O^–
h. I^– or Cl^–

Verified video answer for a similar problem:

Key Concepts

Nucleophilicity

Solvent Effects in SN2 Reactions

Steric Hindrance