Which order is correct for both nucleophilicity and basicity ?

Options

A. `Cl^(-) lt I^(-)`
B. `H_(2)O lt H_(2)S`
C. `MeO^(-) gt F^(-)`
D. `EtO^(-) lt OH^(-)`

Explanation

To determine the correct order for both nucleophilicity and basicity, we will analyze the options provided one by one.

### Step-by-Step Solution:

1. **Understanding Basicity and Nucleophilicity**:
- **Basicity** refers to the ability of a species to accept protons (H⁺ ions).
- **Nucleophilicity** refers to the ability of a species to donate a pair of electrons to an electrophile.

2. **Analyzing Option A: Chloride Ion (Cl⁻) and Iodide Ion (I⁻)**:
- **Basicity**: Basicity decreases down the group in the periodic table due to a decrease in charge density. Therefore, Cl⁻ is more basic than I⁻.
- **Nucleophilicity**: Nucleophilicity increases down the group. Thus, I⁻ is more nucleophilic than Cl⁻.
- **Conclusion**: The orders are opposite, making this option false.

3. **Analyzing Option B: Water (H₂O) and Hydrogen Sulfide (H₂S)**:
- **Basicity**: H₂S is less basic than H₂O, as basicity decreases down the group.
- **Nucleophilicity**: The nucleophilicity will also follow the same trend, with H₂S being more nucleophilic than H₂O.
- **Conclusion**: The orders are opposite, making this option false.

4. **Analyzing Option C: Methoxide Ion (MeO⁻) and Fluoride Ion (F⁻)**:
- **Basicity**: Methoxide ion is more basic than fluoride ion because the negative charge on oxygen is less electronegative than that on fluorine, allowing easier donation of electrons.
- **Nucleophilicity**: Methoxide ion is also more nucleophilic than fluoride ion for the same reason; it can easily donate its electrons.
- **Conclusion**: Both basicity and nucleophilicity follow the same order, making this option correct.

5. **Analyzing Option D: Ethoxide Ion (EtO⁻) and Hydroxide Ion (OH⁻)**:
- **Basicity**: Ethoxide ion is more basic than hydroxide ion due to the electron-donating effect of the ethyl group, which increases negative charge density.
- **Nucleophilicity**: However, nucleophilicity decreases with increased bulkiness. Therefore, hydroxide ion is more nucleophilic than ethoxide ion.
- **Conclusion**: The orders are opposite, making this option false.

### Final Answer:
The correct order for both nucleophilicity and basicity is given in **Option C: Methoxide Ion (MeO⁻) > Fluoride Ion (F⁻)**.

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