Which of the following group show `-m` and `-I` effect?

Options

A. `-NO_(2)`
B. `-NH_(2)`
C. `-OH`
D. `-F`

Answer

To determine which of the following groups shows both the -M (minus mesomeric) and -I (minus inductive) effects, we need to analyze the nature of each group provided in the options.

### Step-by-Step Solution:

1. **Understand the Effects**:
- **-M Effect (Minus Mesomeric Effect)**: This effect is exhibited by electron-withdrawing groups that can stabilize a negative charge through resonance. It involves the delocalization of electrons through pi bonds or lone pairs.
- **-I Effect (Minus Inductive Effect)**: This effect is due to the polarization of sigma bonds caused by electronegative atoms or groups that withdraw electron density towards themselves.

2. **Analyze Each Group**:
- **Group A: NO2 (Nitro Group)**:
- The nitro group is an electron-withdrawing group due to the electronegativity of oxygen and nitrogen.
- It can withdraw electron density through resonance (showing -M effect) and also through the inductive effect (-I effect).
- **Conclusion**: NO2 shows both -M and -I effects.

- **Group B: NH2 (Amino Group)**:
- The amino group has lone pairs on nitrogen that can donate electrons, exhibiting a +M effect (positive mesomeric effect).
- It does not show -M or -I effects.
- **Conclusion**: NH2 does not show -M or -I effects.

- **Group C: OH (Hydroxyl Group)**:
- The hydroxyl group also has lone pairs on oxygen that can donate electrons, showing a +M effect.
- It does not exhibit -M or -I effects.
- **Conclusion**: OH does not show -M or -I effects.

- **Group D: Cl (Chloro Group)**:
- Chlorine is electronegative and can withdraw electron density through the inductive effect (-I effect).
- However, it can also donate its lone pairs, which gives it a +M effect.
- **Conclusion**: Cl does not show -M effect.

3. **Final Conclusion**:
- Among the groups analyzed, only the **NO2 group** shows both -M and -I effects. Therefore, the correct answer is **Option A: NO2**.