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

Options

A. `.^(Θ)OH`
B. `.^(Θ)OR`
C. `.^(Θ)OC_(6)H_(5)`
D.

Explanation

To determine which of the given species can act as the strongest base, we will analyze the options provided and apply the concept of conjugate acids and bases. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the Concept of Conjugate Acids and Bases
A strong acid has a weak conjugate base, and a strong base has a weak conjugate acid. Therefore, to find the strongest base among the given options, we can look for the weakest acid.

**Hint:** Recall that the strength of an acid is inversely related to the strength of its conjugate base.

### Step 2: Identify the Given Species
The species given in the question are:
1. OH⁻ (hydroxide ion)
2. OR⁻ (alkoxide ion)
3. OC₆H₅⁻ (phenoxide ion)
4. O⁻ attached to a benzene ring with a nitro group in the para position (4-hydroxy nitrobenzene)

**Hint:** Write down the structures of each species to visualize their acidity.

### Step 3: Determine the Conjugate Acids
Next, we will identify the conjugate acids for each of the anions:
1. For OH⁻, the conjugate acid is H₂O (water).
2. For OR⁻, the conjugate acid is ROH (alcohol).
3. For OC₆H₅⁻, the conjugate acid is C₆H₅OH (phenol).
4. For O⁻ (from 4-hydroxy nitrobenzene), the conjugate acid is 4-nitrophenol.

**Hint:** Consider the strength of these acids; weaker acids correspond to stronger bases.

### Step 4: Compare the Acidity of the Conjugate Acids
Now we will evaluate the acidity of the conjugate acids:
- Water (H₂O) is a weak acid.
- Alcohol (ROH) is weaker than water.
- Phenol (C₆H₅OH) is more acidic than alcohol.
- 4-nitrophenol is even more acidic due to the electron-withdrawing effect of the nitro group.

**Hint:** Recall that the presence of electron-withdrawing groups increases acidity.

### Step 5: Identify the Weakest Acid
From the analysis:
- The weakest acid among the conjugate acids is alcohol (ROH).
- Therefore, the strongest base will be the conjugate base of the weakest acid, which is OR⁻ (alkoxide ion).

**Hint:** The weaker the acid, the stronger its conjugate base.

### Step 6: Conclusion
Thus, the strongest base among the given options is the alkoxide ion (OR⁻).

**Final Answer:** The strongest base is option 2, OR⁻ (alkoxide ion).