The decreasing order of nucleophilicity for the folllwing anions is
`CH_(3)CO_(2)^(-), CH_(3)O^(-), C_(6)H_(5)O^(-), NO_(3)`

Options

A. `CH_(3)CO_(2)^(-)gt CH_(3)O^(-)gt C_(6)H_(5)O^(-) gt NO_(3)^(-)`
B. `CH_(3)O^(-) gt NO_(3)^(-) gt C_(6)H_(5)O^(-)gt CH_(3)CO_(2)^(-)`
C. `CH_(3)O^(-) gt C_(6)H_(5)O^(-) gt CH_(3)CO_(2)^(-) gt NO_(3)^(-)`
D. `C_(6)H_(5)O^(-) gt CH_(3)O^(-) gt NO_(3)^(-) gt CH_(3)CO_(2)^(-)`

Answer

To determine the decreasing order of nucleophilicity for the given anions: \( CH_3CO_2^-, CH_3O^-, C_6H_5O^-, NO_3^- \), we need to analyze the stability of the negative charge in each anion. The less stable the negative charge, the more nucleophilic the species will be, as it is more willing to donate the electron pair.

### Step-by-Step Solution:

1. **Analyze \( CH_3CO_2^- \) (Acetate Ion)**:
- The acetate ion has resonance structures. The negative charge can be delocalized over two oxygen atoms. This delocalization stabilizes the negative charge, making it less nucleophilic compared to a species with a localized negative charge.
- **Conclusion**: Moderate nucleophilicity due to resonance stabilization.

2. **Analyze \( CH_3O^- \) (Methoxide Ion)**:
- The methoxide ion has a localized negative charge on the oxygen atom with no resonance stabilization. This makes the negative charge highly available for donation, increasing its nucleophilicity.
- **Conclusion**: High nucleophilicity due to the absence of resonance.

3. **Analyze \( C_6H_5O^- \) (Phenoxide Ion)**:
- The phenoxide ion has resonance structures as well, where the negative charge can be delocalized into the aromatic ring. Although it is more stable than methoxide due to resonance, it is less nucleophilic than methoxide because the negative charge is somewhat delocalized.
- **Conclusion**: Lower nucleophilicity than methoxide but higher than acetate due to resonance.

4. **Analyze \( NO_3^- \) (Nitrate Ion)**:
- The nitrate ion has resonance structures where the negative charge is delocalized over three oxygen atoms. This extensive resonance stabilization makes the negative charge very stable and thus not very available for nucleophilic attack.
- **Conclusion**: Lowest nucleophilicity due to high resonance stabilization.

### Final Order of Nucleophilicity:
Based on the analysis, the decreasing order of nucleophilicity for the given anions is:
\[ CH_3O^- > C_6H_5O^- > CH_3CO_2^- > NO_3^- \]