Which of the following species can act as the strongest base ?

Options

A. `""^-OH`
B. `""^OR`
C. `""^OC_6H_5`
D.

Explanation

To determine which of the given species can act as the strongest base, we will analyze each option based on their conjugate acids and the stability of the resulting species after deprotonation.

### Step-by-Step Solution:

1. **Identify the Species**: The options provided are:
- A) OH⁻ (hydroxide ion)
- B) OR⁻ (alkoxide ion)
- C) O⁻ (oxide ion)
- D) C₆H₅O⁻ (phenoxide ion)

2. **Understand the Concept of Conjugate Bases**:
- A weak acid has a strong conjugate base. Therefore, to determine which species is the strongest base, we need to consider the acidity of their corresponding acids.
- The strength of a base is inversely related to the strength of its conjugate acid.

3. **Analyze Each Species**:
- **A) OH⁻**: This is the conjugate base of water (H₂O), which is a weak acid.
- **B) OR⁻**: This is the conjugate base of alcohols (ROH), which are generally weak acids.
- **C) O⁻**: This is the conjugate base of very strong acids (like H₂O), making it a strong base.
- **D) C₆H₅O⁻**: This is the conjugate base of phenol (C₆H₅OH), which is a weak acid.

4. **Compare the Acidity**:
- **OH⁻** is derived from a weak acid (water).
- **OR⁻** is derived from alcohols, which are also weak acids.
- **O⁻** is derived from a very strong acid, making it a strong base.
- **C₆H₅O⁻** is derived from phenol, which is a weak acid.

5. **Determine the Strongest Base**:
- The strongest base will be the one that corresponds to the weakest acid. Since O⁻ is derived from a very strong acid, it is a strong base.
- However, OR⁻ (alkoxide ion) is derived from alcohols, which are weak acids, making OR⁻ a stronger base than OH⁻ and C₆H₅O⁻.

6. **Conclusion**: Among the given species, **B) OR⁻ (alkoxide ion)** is the strongest base because it is derived from a weak acid (alcohol), making it a stronger base than the others.

### Final Answer:
**B) OR⁻ (alkoxide ion)** is the strongest base.