Fluoride ion works as a good leaving group in aromatic nucleophilic substitution of 2,4-dinitro fluorobenzene, even though it is a poor leaving group in aliphatic `S_(N)1andS_(N)2` mechanisms.

Explanation

### Step-by-Step Solution:

1. **Understanding the Context**:
- The question asks why the fluoride ion (F⁻) acts as a good leaving group in the aromatic nucleophilic substitution of 2,4-dinitrofluorobenzene, despite being a poor leaving group in aliphatic SN1 and SN2 mechanisms.

2. **Aromatic Nucleophilic Substitution Mechanism**:
- In aromatic nucleophilic substitution, the nucleophile attacks the aromatic ring, which leads to the formation of a Meisenheimer complex (an intermediate).
- For 2,4-dinitrofluorobenzene, the presence of two nitro (NO₂) groups at the 2 and 4 positions enhances the electrophilicity of the aromatic ring, making it more susceptible to nucleophilic attack.
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