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

Options

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

Answer

To determine which of the following groups exhibit both -M (minus mesomeric) and -I (minus inductive) effects, we will analyze each group mentioned in the question.

### Step 1: Analyze the NO2 group
- The structure of the nitro group (NO2) shows that nitrogen (N) is bonded to two oxygen (O) atoms.
- Nitrogen is more electronegative than carbon and will withdraw electron density through the inductive effect (-I).
- Additionally, the nitrogen has a lone pair that can participate in resonance, pulling electron density from the aromatic system, which indicates a -M effect.

**Conclusion for NO2:** It shows both -M and -I effects.

### Step 2: Analyze the NH2 group
- The amino group (NH2) has a nitrogen atom with a lone pair.
- This lone pair can be donated into the aromatic system, which indicates a +M (positive mesomeric) effect.
- However, since nitrogen is less electronegative than carbon, it does not withdraw electron density through the inductive effect. Therefore, it does not show -I effect.

**Conclusion for NH2:** It shows +M effect and does not show -M or -I effects.

### Step 3: Analyze the OH group
- The hydroxyl group (OH) has an oxygen atom with a lone pair.
- Similar to NH2, the lone pair on oxygen can be donated into the aromatic system, indicating a +M effect.
- Oxygen is also less electronegative than carbon, so it does not withdraw electron density through the inductive effect, thus it does not show -I effect.

**Conclusion for OH:** It shows +M effect and does not show -M or -I effects.

### Step 4: Analyze the Cl group
- The chlorine atom (Cl) is a halogen and is electronegative, which means it will withdraw electron density through the inductive effect (-I).
- However, chlorine also has lone pairs that can participate in resonance, which means it can donate electron density into the aromatic system, indicating a +M effect.

**Conclusion for Cl:** It shows +M effect and -I effect, but not -M effect.

### Final Conclusion
From the analysis:
- Only the NO2 group shows both -M and -I effects.
- The other groups (NH2, OH, Cl) do not exhibit both effects simultaneously.

### Answer: The group that shows -M and -I effects is NO2.

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