Statement-I: Tert-Butoxide is a stronger base than `OH^(-)` or `C_(2)H_(5)O^(-)` ion but is a much poorer nucleophile
Because
Statement-II: A negatively charged ions is always more powerful nucleophile than its conjugate acid.

Options

A. Statement-I is True, Statement-II is True : Statement-II is a correct explanation for Statement-I
B. Statement-I is True, Statement-II is True : Statement-II is `NOT` a correct explanation for Statement-I
C. Statement-I is True, Statement-II is False.
D. Statement-I is False, Statement-II is True.

Answer

To analyze the given statements, we will break down the reasoning behind each statement step by step.

### Step 1: Understanding Statement-I
**Statement-I:** Tert-Butoxide is a stronger base than OH⁻ or C₂H₅O⁻ but is a much poorer nucleophile.

1. **Structure of Tert-Butoxide:** Tert-butoxide (t-BuO⁻) has the structure (CH₃)₃CO⁻. It has three methyl groups attached to the oxygen.
2. **Basicity:** The presence of three electron-donating methyl groups increases the electron density on the oxygen atom, making t-BuO⁻ a stronger base compared to OH⁻ (hydroxide) and C₂H₅O⁻ (ethoxide). The +I effect from the alkyl groups enhances its basicity.
3. **Nucleophilicity:** Despite being a strong base, t-BuO⁻ is a poor nucleophile. This is due to steric hindrance caused by the bulky tert-butyl group, which makes it difficult for the nucleophile to approach and attack electrophilic centers.

### Step 2: Understanding Statement-II
**Statement-II:** A negatively charged ion is always a more powerful nucleophile than its conjugate acid.

1. **Conjugate Acids and Bases:** For any acid-base pair, the conjugate acid is formed by adding a proton (H⁺) to the base. For example, the conjugate acid of OH⁻ is H₂O, and the conjugate acid of C₂H₅O⁻ is C₂H₅OH.
2. **Nucleophilicity Comparison:** Negatively charged ions (like OH⁻ or C₂H₅O⁻) have a complete negative charge and are generally better nucleophiles than their corresponding neutral conjugate acids (like H₂O or C₂H₅OH). This is because the negative charge increases the electron density, making it more reactive towards electrophiles.

### Conclusion
- **Statement-I is True:** Tert-butoxide is indeed a stronger base than hydroxide or ethoxide but is a poorer nucleophile due to steric hindrance.
- **Statement-II is True:** A negatively charged ion is generally a more powerful nucleophile than its conjugate acid because of the presence of a complete negative charge.

### Final Answer
Both statements are true, but Statement-II does not explain Statement-I. Therefore, the answer is:
**Option B:** Statement I is true, Statement II is true, but Statement II is not the correct explanation for Statement I.

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