Which among the following is a meta directing group?

Options

A. `-CH_(3)`
B. `-underset(O)underset(||)overset(O)overset(||)(S)-O-H`
C. `-O-CH_(3)`
D. `-NH_(2)`

Answer

To determine which among the given options is a meta directing group, we need to analyze each option based on their electronic effects on a benzene ring. Meta directing groups are those that increase the electron density at the meta position of the benzene ring.

### Step-by-Step Solution:

1. **Understanding Meta Directing Groups**:
- Meta directing groups are substituents that, when attached to a benzene ring, direct incoming electrophiles to the meta position relative to themselves. They typically withdraw electron density from the ring.

2. **Analyzing Each Option**:
- **Option 1: CH3 (Methyl Group)**:
- The methyl group (CH3) is an electron-donating group (due to +I effect). It increases electron density at the ortho and para positions, thus making it an ortho-para directing group, not a meta directing group.

- **Option 2: SO3H (Sulfonic Acid Group)**:
- The sulfonic acid group (SO3H) is an electron-withdrawing group due to the presence of electronegative oxygen atoms. It decreases electron density at the ortho and para positions, while increasing it at the meta position. Therefore, this is a meta directing group.

- **Option 3: OCH3 (Methoxy Group)**:
- The methoxy group (OCH3) is an electron-donating group due to resonance (+R effect). It increases electron density at the ortho and para positions, making it an ortho-para directing group, not a meta directing group.

- **Option 4: NH2 (Amino Group)**:
- The amino group (NH2) is also an electron-donating group due to resonance (+R effect). It increases electron density at the ortho and para positions, making it an ortho-para directing group, not a meta directing group.

3. **Conclusion**:
- After analyzing all the options, we find that the only meta directing group among the given options is **SO3H**.

### Final Answer:
**SO3H is a meta directing group.**