Electrophile `NO_(2)^(o+)` attacks the following in which cases `NO_(2)^(o+)` will be at meta position:

Options

A.
B.
C.
D.

Answer

To determine the positions where the nitronium ion (`NO2^+`) will attack a benzene ring, we need to analyze the substituents (X groups) present on the ring and their effects on the electron density. The key is to identify whether these substituents are electron-donating or electron-withdrawing.

### Step-by-Step Solution:

1. **Identify the Nature of Substituents**:
- Determine if the substituent (X) on the benzene ring is an electron-donating group (EDG) or an electron-withdrawing group (EWG).
- EDGs increase electron density on the ring, favoring electrophilic attack at the ortho and para positions.
- EWGs decrease electron density on the ring, favoring electrophilic attack at the meta position.

2. **Analyze the Effects of EDGs**:
- If the substituent is an EDG (like -OH, -OCH3, -NH2), the electron density at the ortho and para positions increases, making them more reactive towards electrophiles. Therefore, the nitronium ion will not attack at the meta position.

3. **Analyze the Effects of EWGs**:
- If the substituent is an EWG (like -NO2, -CN, -COOH, -CF3), it pulls electron density away from the ring. This results in a decrease in electron density at the ortho and para positions, making the meta position relatively more electron-rich and favorable for attack by the nitronium ion.

4. **Conclusion**:
- The nitronium ion will attack the meta position in the presence of electron-withdrawing groups. Therefore, for the given question, we need to find the options where the substituents are EWGs.

### Final Answer:
The nitronium ion (`NO2^+`) will attack the meta position in the presence of electron-withdrawing groups. Thus, options with EWGs will lead to meta substitution.