Strongest nucleophile is

Options

A. `RNH_(2)`
B. `ROH`
C. `C_(6) H_(5) O^(-)`
D. `CH_(3) O^(-)`

Explanation

To determine the strongest nucleophile, we need to understand what a nucleophile is and the factors that influence nucleophilicity.

### Step-by-Step Solution:

1. **Definition of Nucleophile**:
A nucleophile is a species that donates an electron pair to form a chemical bond in a reaction. Nucleophiles are typically negatively charged or neutral molecules with lone pairs of electrons.

2. **Factors Affecting Nucleophilicity**:
Several factors influence the strength of a nucleophile:
- **Charge**: Negatively charged species are generally stronger nucleophiles than their neutral counterparts.
- **Electronegativity**: Less electronegative atoms are better nucleophiles because they hold onto their electrons less tightly.
- **Solvent Effects**: In polar protic solvents, nucleophilicity decreases with increasing size due to solvation effects. In polar aprotic solvents, larger nucleophiles are stronger because they are less solvated.

3. **Comparison of Common Nucleophiles**:
Common nucleophiles include:
- \( \text{OH}^- \) (hydroxide)
- \( \text{CH}_3\text{O}^- \) (methoxide)
- \( \text{I}^- \) (iodide)
- \( \text{Br}^- \) (bromide)
- \( \text{Cl}^- \) (chloride)

4. **Identifying the Strongest Nucleophile**:
Among the common nucleophiles, \( \text{CH}_3\text{O}^- \) (methoxide) is often cited as one of the strongest nucleophiles due to its negative charge and the presence of a lone pair of electrons on the oxygen atom. However, in some contexts, \( \text{Cs}_3\text{O}^- \) (cesium oxide) is mentioned as the strongest nucleophile because of the larger size of cesium, which makes the negative charge more available for donation.

5. **Conclusion**:
Therefore, based on the information provided and the factors influencing nucleophilicity, \( \text{Cs}_3\text{O}^- \) is considered one of the strongest nucleophiles.

### Final Answer:
The strongest nucleophile is \( \text{Cs}_3\text{O}^- \) (cesium oxide).