The most reactive nucleophile among the following is :

Options

A. `CH_(3)O^(-)`
B. `C_(6)H_(5)O^(-)`
C. `(CH_(3))_(2)CHO^(-)`
D. `(CH_(3))_(3)CO^(-)`

Explanation

To determine the most reactive nucleophile among the given options, we need to analyze the structure and electron-donating effects of each nucleophile. Let's break down the steps:

### Step 1: Identify the Nucleophiles
List the nucleophiles provided in the options:
1. Methoxide ion (CH3O⁻)
2. Phenoxide ion (C6H5O⁻)
3. Alkoxide with two methyl groups (C2H5O⁻)
4. Alkoxide with three methyl groups (C3H9O⁻)

### Step 2: Understand Nucleophilicity
Nucleophilicity is the ability of a species to donate an electron pair to an electrophile. The reactivity of nucleophiles is influenced by:
- The presence of electron-donating groups (which increase electron density).
- The stability of the nucleophile (more stable nucleophiles are less reactive).

### Step 3: Analyze Each Nucleophile
1. **Methoxide ion (CH3O⁻)**: This has one methyl group, which provides some electron-donating effect but is limited.

2. **Phenoxide ion (C6H5O⁻)**: The negative charge on oxygen can participate in resonance with the aromatic ring, which stabilizes the nucleophile and reduces its reactivity.

3. **Alkoxide with two methyl groups (C2H5O⁻)**: This has two methyl groups, which provide a moderate electron-donating effect, increasing its nucleophilicity compared to methoxide.

4. **Alkoxide with three methyl groups (C3H9O⁻)**: This has three methyl groups, which significantly increase the electron density on oxygen due to the +I effect of the methyl groups. This makes it a very strong nucleophile.

### Step 4: Compare Reactivity
- The **methoxide ion** is less reactive due to having only one methyl group.
- The **phenoxide ion** is stabilized by resonance, making it less reactive.
- The **alkoxide with two methyl groups** is more reactive than methoxide but still less than the one with three methyl groups.
- The **alkoxide with three methyl groups** has the highest electron density due to the presence of three electron-donating methyl groups, making it the most reactive nucleophile.

### Conclusion
The most reactive nucleophile among the given options is the alkoxide with three methyl groups (C3H9O⁻).

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