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 anions CH₃CO₂⁻, CH₃O⁻, C₆H₅O⁻, and NO₃⁻, we need to analyze the stability of these anions and their ability to donate electrons. Here’s a step-by-step solution:

### Step 1: Understand Nucleophilicity
Nucleophilicity refers to the ability of a species to donate electrons. Stronger nucleophiles are less stable because they are more willing to donate their electrons.

### Step 2: Analyze Each Anion
1. **CH₃CO₂⁻ (Acetate Ion)**:
- This anion has resonance. The negative charge is delocalized over two oxygen atoms.
- While it can donate electrons, the resonance stabilizes the negative charge, making it less nucleophilic compared to anions without resonance.

2. **CH₃O⁻ (Methoxide Ion)**:
- This anion does not have resonance. The negative charge is localized on the oxygen atom.
- Because there is no resonance to stabilize the negative charge, it is more willing to donate electrons, making it a strong nucleophile.

3. **C₆H₅O⁻ (Phenoxide Ion)**:
- This anion also has resonance. The negative charge can be delocalized into the aromatic ring.
- The presence of resonance decreases its nucleophilicity compared to CH₃O⁻, but it is still more nucleophilic than CH₃CO₂⁻ because the resonance is less effective than in acetate.

4. **NO₃⁻ (Nitrate Ion)**:
- This anion has resonance as well, with the negative charge delocalized over three oxygen atoms.
- The negative charge is highly stabilized due to this delocalization, making it the least nucleophilic of the four anions.

### Step 3: Order the Anions Based on Nucleophilicity
Based on the analysis:
- CH₃O⁻ is the most nucleophilic because it has no resonance stabilization.
- C₆H₅O⁻ follows, as it has resonance but is still more reactive than CH₃CO₂⁻.
- CH₃CO₂⁻ comes next due to resonance stabilizing the negative charge.
- NO₃⁻ is the least nucleophilic due to extensive resonance stabilization.

### Final Order of Nucleophilicity:
The decreasing order of nucleophilicity is:
**CH₃O⁻ > C₆H₅O⁻ > CH₃CO₂⁻ > NO₃⁻**