Arrange the following in correct activating order towards `EAS` -
`{:(underset(I)(-NHCOCH_(3)),,underset(II)(-O-overset(O)overset(||)C-CH_(3)),,underset(III)(-overset(+)(NR_(3))),,underset(IV)(-NH_(2))):}`

Options

A. `IIIltIltIIltIV`
B. `IVltIltIIltIII`
C. `IIIltIIltIltIV`
D. `IIltIIIltIltIV`

Answer

To arrange the given substituents in the correct activating order towards Electrophilic Aromatic Substitution (EAS), we need to analyze the electron-donating or electron-withdrawing nature of each group. Here's the step-by-step solution:

### Step 1: Identify the nature of each substituent
1. **-NH2 (Amino group)**: This is a strong electron-donating group (EDG) because the nitrogen atom has a lone pair of electrons that can be donated to the aromatic ring, increasing its electron density.

2. **-NHCOCH3 (Amide group)**: This group is a moderate EDG. While the carbonyl (C=O) is electron-withdrawing, the nitrogen still has a lone pair that can donate electrons, making it less activating than -NH2 but still an activator.

3. **-O=C-CH3 (Acetyl group)**: This is a weak electron-withdrawing group (EWG). The carbonyl group pulls electron density away from the ring, making it a deactivator, but it is less deactivating than the next group.

4. **-NR3 (Tertiary amine)**: This group is a strong electron-withdrawing group due to the positive charge on nitrogen when it is bonded to three alkyl groups. It decreases the electron density of the aromatic ring significantly, making it the weakest activator or the strongest deactivator.

### Step 2: Arrange the groups based on their activating effects
Based on the analysis:
- **Strongest Activator**: -NH2 (Amino group)
- **Moderate Activator**: -NHCOCH3 (Amide group)
- **Weak Activator**: -O=C-CH3 (Acetyl group)
- **Strongest Deactivator**: -NR3 (Tertiary amine)

### Final Order
The correct order of activating effects towards EAS from strongest to weakest is:
1. **-NH2 (I)**
2. **-NHCOCH3 (II)**
3. **-O=C-CH3 (III)**
4. **-NR3 (IV)**

Thus, the final answer is:
**I > II > III > IV**