Which of the following group show `+M` and `-l` effect?

Options

A. `-underset(O)underset(||)C-F`
B. `-underset(O)underset(||)C-OR`
C. `-O^(Theta)`
D. `-OH`

Answer

To determine which of the following groups show both +M (mesomeric effect) and -I (inductive effect), we need to analyze the effects of each functional group based on their electron-donating or electron-withdrawing properties.

### Step-by-Step Solution:

1. **Understand the Terms:**
- **+M Effect (Mesomeric Effect):** This effect occurs when a group can donate electron density through resonance. It typically involves lone pairs or π bonds adjacent to a positively charged or electron-deficient atom.
- **-I Effect (Inductive Effect):** This effect occurs when a group withdraws electron density through σ bonds due to electronegativity. Electronegative atoms or groups exhibit this effect.

2. **Analyze Each Group:**
- **Group 1: C=O (with F)**
- Fluorine (F) is highly electronegative, which means it withdraws electron density. Thus, it shows a -I effect. However, it cannot donate electron density through resonance, so it does not show +M effect.
- **Conclusion:** Only -I effect.

- **Group 2: C=O (with OR)**
- The alkoxy group (OR) can donate electron density through resonance due to the lone pair on oxygen, showing a +M effect. However, it does not withdraw electron density, so it does not show -I effect.
- **Conclusion:** Only +M effect.

- **Group 3: O- (alkoxide)**
- The alkoxide ion (O-) has a high electron density due to the negative charge. It can donate electron density through resonance (+M effect) but does not withdraw electron density, hence it does not show -I effect.
- **Conclusion:** Only +M effect.

- **Group 4: OH (Hydroxyl group)**
- The hydroxyl group (OH) has an electronegative oxygen atom that can withdraw electron density through σ bonds, showing a -I effect. Additionally, the lone pair on oxygen can donate electron density through resonance, showing a +M effect.
- **Conclusion:** Shows both +M and -I effects.

3. **Final Answer:**
- The group that shows both +M and -I effects is the **hydroxyl group (OH)**.