Which among the following is deactivating group ?

Options

A. `-Cl`
B. `-OR`
C. `-NH_2`
D. `-NHR`

Answer

To determine which among the given groups is a deactivating group, we need to analyze the nature of each group and its effect on the electron density of the benzene ring. Deactivating groups are those that withdraw electron density from the aromatic ring, thereby slowing down the rate of electrophilic aromatic substitution reactions.

### Step-by-Step Solution:

1. **Understanding Deactivating Groups**:
- Deactivating groups are typically electron-withdrawing groups. They decrease the electron density on the benzene ring, making it less reactive towards electrophiles.

2. **Identifying the Given Groups**:
- The groups provided in the question are: Cl (Chlorine), NH2 (Amino), NH (Amine), and R (Alkyl group).

3. **Analyzing Each Group**:
- **Chlorine (Cl)**: This is a halogen. Halogens are known to be deactivating groups because they withdraw electron density through their electronegativity, despite having lone pairs that can donate electron density. Therefore, Cl is a deactivating group.
- **Amino Group (NH2)**: This group is an activating group because it donates electron density to the benzene ring through resonance.
- **Amine Group (NH)**: Similar to the amino group, this is also an activating group as it donates electron density to the ring.
- **Alkyl Group (R)**: Alkyl groups are generally activating groups because they donate electron density to the benzene ring through hyperconjugation.

4. **Conclusion**:
- Among the given options, the only deactivating group is **Chlorine (Cl)**.

### Final Answer:
- The deactivating group among the options is **Cl (Chlorine)**.

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