Which among the following is not a mets directing group?

Options

A. `-NO_(2)`
B. `-SO_(3)H`
C. `-COOH`
D. `-OH`

Answer

To determine which among the given options is not a meta-directing group, we need to analyze the nature of each substituent attached to the benzene ring.

### Step-by-Step Solution:

1. **Understanding Directing Effects**:
- Substituents on a benzene ring can be classified as either ortho-para directing or meta directing.
- Ortho-para directing groups are typically electron-donating groups (EDGs) that stabilize the carbocation intermediate formed during electrophilic aromatic substitution.
- Meta directing groups are generally electron-withdrawing groups (EWGs) that destabilize the carbocation intermediate.

2. **Identifying Electron-Withdrawing Groups**:
- Common electron-withdrawing groups include nitro (NO2), sulfonyl (SO3H), and aldehyde (COH) groups. These groups pull electron density away from the benzene ring, leading to a meta directing effect.

3. **Analyzing Each Option**:
- **Option 1: NO2** - This is an electron-withdrawing group and exhibits both -I (inductive effect) and -M (mesomeric effect). Therefore, it is a meta-directing group.
- **Option 2: SO3H** - This is also an electron-withdrawing group, showing -I and -M effects, making it a meta-directing group.
- **Option 3: COH** - The aldehyde group is an electron-withdrawing group as well, exhibiting -I and -M effects, thus it is also a meta-directing group.
- **Option 4: OH** - The hydroxyl group is an electron-donating group due to the presence of lone pairs on oxygen. It shows +M effect (due to resonance) and -I effect (due to electronegativity), but the +M effect dominates, making it an ortho-para directing group.

4. **Conclusion**:
- Among the options provided, the hydroxyl group (OH) is not a meta-directing group. It is an ortho-para directing group.

### Final Answer:
The correct option that is not a meta-directing group is **Option 4: OH**.