Arrange nucleophilicity of given species in decreasing order:
(1) `CH_(3)-overset(ө)CH_(2)`
(2) `CH_(3)-overset(ө)O`
(3) `overset(ө)NH_(2)`
(4) `overset(ө)F`

Options

A. 1, 3 ,2 4
B. 1, 3, 4, 2
C. 3, 1, 2, 4
D. 3, 1, 4, 2

Answer

To arrange the nucleophilicity of the given species in decreasing order, we need to analyze each species based on its ability to donate a lone pair of electrons. Nucleophilicity is influenced by several factors, including charge, electronegativity, and the stability of the species.

### Step-by-step Solution:

1. **Identify the Species**:
The given species are:
- (1) `CH₃-CH₂` (Ethyl anion)
- (2) `CH₃-O` (Methoxy anion)
- (3) `NH₂` (Amide anion)
- (4) `F` (Fluoride anion)

2. **Assess the Charge and Electronegativity**:
- **Fluoride (F)**: Has a negative charge and is highly electronegative. This makes the negative charge on F very stable, thus reducing its nucleophilicity.
- **Amide (NH₂)**: The negative charge on nitrogen is less stable than on oxygen but more stable than on carbon. Thus, it has moderate nucleophilicity.
- **Methoxy (O)**: The negative charge on oxygen is less stable than on nitrogen but more stable than on carbon. It has a higher nucleophilicity than both F and NH₂.
- **Ethyl (CH₃-CH₂)**: The negative charge on carbon is the least stable compared to the other species, making it the most nucleophilic.

3. **Rank the Nucleophilicity**:
Based on the stability of the negative charge:
- **Most Nucleophilic**: `CH₃-CH₂` (1)
- **Next**: `NH₂` (3)
- **Then**: `CH₃-O` (2)
- **Least Nucleophilic**: `F` (4)

4. **Final Order**:
The decreasing order of nucleophilicity is:
1. `CH₃-CH₂` (1)
2. `NH₂` (3)
3. `CH₃-O` (2)
4. `F` (4)

### Conclusion:
The final decreasing order of nucleophilicity is:
`CH₃-CH₂ > NH₂ > CH₃-O > F`