(•) For each pair, choose the nucleophile that would react most quickly in an Sₙ2 reaction (assume H₂O is the solvent).


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Verified step by step guidance

1. Identify the nucleophiles in each pair. Nucleophiles are species that donate an electron pair to form a chemical bond in relation to a reaction.
2. Consider the solvent effect. In this case, H₂O is a polar protic solvent, which can stabilize anions through hydrogen bonding, potentially affecting nucleophilicity.
3. Evaluate the basicity of each nucleophile. Generally, stronger bases are better nucleophiles in polar protic solvents.
4. Consider the steric hindrance of each nucleophile. Less sterically hindered nucleophiles are more effective in Sₙ2 reactions because they can more easily approach the electrophile.
5. Compare the nucleophiles based on the above factors to determine which one would react more quickly in an Sₙ2 reaction.

Key Concepts

Nucleophilicity

Nucleophilicity refers to the ability of a species to donate an electron pair to an electrophile, forming a chemical bond. In Sₙ2 reactions, stronger nucleophiles react more quickly due to their higher electron density and better ability to stabilize the transition state. Factors influencing nucleophilicity include charge, electronegativity, and solvent effects.

Sₙ2 Mechanism

The Sₙ2 (substitution nucleophilic bimolecular) mechanism involves a single concerted step where the nucleophile attacks the electrophile while simultaneously displacing a leaving group. This reaction is characterized by a backside attack, leading to inversion of configuration at the chiral center. The rate of the reaction depends on both the nucleophile and the substrate.

Solvent Effects

The choice of solvent can significantly influence the rate of Sₙ2 reactions. Polar protic solvents, like water, can stabilize ions and slow down the reaction by solvation of the nucleophile, while polar aprotic solvents enhance nucleophilicity by not solvate the nucleophile as effectively. Understanding solvent effects is crucial for predicting reaction outcomes in nucleophilic substitutions.