For each pair, choose the more reactive nucleophile.
(a)

Verified step by step guidance

1. Step 1: Understand the concept of nucleophilicity. Nucleophilicity refers to the ability of a species to donate a pair of electrons to an electrophile. It is influenced by factors such as charge, electronegativity, solvent effects, and steric hindrance.
2. Step 2: Analyze the first nucleophile in the pair. Consider its charge (negative charges generally increase nucleophilicity), electronegativity (lower electronegativity increases nucleophilicity), and size (larger atoms are more polarizable and often better nucleophiles in polar protic solvents).
3. Step 3: Analyze the second nucleophile in the pair using the same criteria as in Step 2. Compare its charge, electronegativity, and size to the first nucleophile.
4. Step 4: Consider the solvent type. In polar protic solvents, larger and more polarizable nucleophiles are more reactive, while in polar aprotic solvents, smaller and less electronegative nucleophiles are more reactive.
5. Step 5: Compare the two nucleophiles based on the above factors and determine which one is more reactive. Remember that the more reactive nucleophile will have a greater tendency to donate its electron pair to an electrophile.

Key Concepts

Nucleophilicity

Nucleophilicity refers to the ability of a species to donate an electron pair to an electrophile during a chemical reaction. It is influenced by factors such as charge, electronegativity, and steric hindrance. Generally, negatively charged species are more nucleophilic than their neutral counterparts, and less sterically hindered nucleophiles are more reactive.

Solvent Effects

The solvent can significantly affect nucleophilicity. In polar protic solvents, nucleophiles are often stabilized by solvation, which can hinder their reactivity. Conversely, in polar aprotic solvents, nucleophiles are less solvated and can exhibit increased reactivity, making the choice of solvent crucial in determining which nucleophile is more reactive.

Comparative Reactivity

When comparing nucleophiles, it is essential to consider their relative reactivity based on their structure and the reaction conditions. Factors such as the presence of electron-donating or withdrawing groups, the size of the nucleophile, and the type of reaction mechanism (e.g., SN1 or SN2) can all influence which nucleophile is more reactive in a given scenario.