Question

Number of deactivating groups among: \( -Cl, -SO_3H, -OH, -NHC_2H_5, -COOCH_3, -CH_3 \)

• A. 4
• B. 3
• C. 2
• D. 1

Hint:

Deactivating groups withdraw electron density, making electrophilic substitution slower.

Answer 1

The Correct Option is B

Step 1: Identify Deactivating Groups 
- Deactivating (-I or -M effects): 
- \( -Cl \), \( -SO_3H \), \( -COOCH_3 \) - Activating (+M or +I effects): 
- \( -OH \), \( -NHC_2H_5 \), \( -CH_3 \)

Step 2: Count Deactivating Groups There are 3 deactivating groups.

Answer 2

Given groups: \( -Cl, -SO_3H, -OH, -NHC_2H_5, -COOCH_3, -CH_3 \)

We need to find the number of deactivating groups among these. Deactivating groups are those that decrease the electron density on the aromatic ring, making it less reactive toward electrophilic substitution.

1. \( -Cl \) (Chloro group):
- Electron-withdrawing by induction but electron-donating by resonance.
- Overall, it is mildly deactivating due to the strong -I effect dominating.
- Counts as deactivating.

2. \( -SO_3H \) (Sulfonic acid group):
- Strong electron-withdrawing group by resonance and induction.
- Strongly deactivating.

3. \( -OH \) (Hydroxyl group):
- Electron-donating by resonance.
- Activating group.

4. \( -NHC_2H_5 \) (Ethylamino group):
- Electron-donating by resonance.
- Activating group.

5. \( -COOCH_3 \) (Ester group):
- Electron-withdrawing group by resonance and induction.
- Deactivating group.

6. \( -CH_3 \) (Methyl group):
- Electron-donating by hyperconjugation.
- Activating group.

Summary:
Deactivating groups = \( -Cl, -SO_3H, -COOCH_3 \)
Number of deactivating groups = 3

Therefore, the correct answer is:
3