Which one the most reactive towards electrophilic reagent:

Options

A.
B.
C.
D.

Answer

To determine which compound is the most reactive towards electrophilic reagents, we need to analyze the electron-donating and electron-withdrawing effects of the substituents attached to the benzene ring in each compound. Here’s a step-by-step breakdown of the reasoning:

### Step 1: Identify the Compounds
We have four compounds with a benzene ring and various substituents. The substituents include:
1. Ethyl group (Et) and a nitrogen atom (NH) attached to a carbonyl (C=O) and a methyl group (CH3).
2. Ethyl group (Et) and a hydroxyl group (OH) attached to a methylene (CH2).
3. Ethyl group (Et), a carbonyl (C=O), and a methyl group (CH3).
4. Ethyl group (Et) and a methoxy group (OCH3).

### Step 2: Analyze Each Compound
- **Compound 1**: The nitrogen has a lone pair that can participate in resonance (donate electrons) but is weakened by the electron-withdrawing effect of the carbonyl group. Thus, it has a moderate +M effect and a +I effect from the ethyl group.

- **Compound 2**: The hydroxyl group (OH) has lone pairs but acts as an electron-withdrawing group due to its -I effect. The ethyl group contributes a +I effect. The overall effect is a weaker electron density on the benzene ring.

- **Compound 3**: Similar to compound 1, the carbonyl (C=O) can withdraw electrons, but the ethyl group still contributes a +I effect. The resonance effect is similar, leading to moderate reactivity.

- **Compound 4**: The methoxy group (OCH3) has a strong +M effect due to the lone pairs on oxygen being able to donate electrons into the benzene ring. The ethyl group contributes a +I effect, enhancing the electron density on the ring.

### Step 3: Compare the Effects
- The strongest electron-donating group (which enhances reactivity towards electrophiles) is the methoxy group in compound 4.
- The other compounds have weaker electron-donating effects due to the presence of electron-withdrawing groups (like carbonyls and hydroxyls).

### Conclusion
Based on the analysis of the electron-donating and withdrawing effects of the substituents, **Compound 4 (with the OCH3 group)** is the most reactive towards electrophilic reagents due to its strong +M effect.

### Final Answer
The most reactive compound towards electrophilic reagents is **Compound 4 (OCH3)**.

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