Which of following species does not exert a resonance effect

Options

A. `C_(6)H_(5)OH`
B. `C_(6)H_(5)Cl`
C. `C_(6)H_(5)NH_(2)`
D. `C_(6)H_(5)NH_(3)`

Explanation

To determine which of the given species does not exert a resonance effect, we need to analyze each option based on the ability of the species to participate in resonance.

### Step-by-Step Solution:

1. **Identify the Species**: We have four species to analyze:
- Option 1: PH.OH (Phenol)
- Option 2: C6H5Cl (Chlorobenzene)
- Option 3: C6H5NH2 (Aniline)
- Option 4: C6H5NH3 (Anilinium ion)

2. **Analyze Option 1: PH.OH (Phenol)**:
- Phenol has a hydroxyl (-OH) group attached to a benzene ring. The lone pair of electrons on the oxygen can delocalize into the aromatic ring, allowing for resonance.
- **Conclusion**: Phenol does exert a resonance effect.

3. **Analyze Option 2: C6H5Cl (Chlorobenzene)**:
- Chlorobenzene has a chlorine atom attached to the benzene ring. The lone pairs on chlorine can also participate in resonance with the aromatic ring, allowing for delocalization of electrons.
- **Conclusion**: Chlorobenzene does exert a resonance effect.

4. **Analyze Option 3: C6H5NH2 (Aniline)**:
- Aniline has an amino (-NH2) group attached to the benzene ring. The lone pair of electrons on the nitrogen can delocalize into the benzene ring, facilitating resonance.
- **Conclusion**: Aniline does exert a resonance effect.

5. **Analyze Option 4: C6H5NH3 (Anilinium ion)**:
- The anilinium ion is formed when aniline accepts a proton (H+), resulting in a positively charged nitrogen. In this case, the nitrogen does not have a lone pair of electrons available for resonance because it is bonded to three hydrogen atoms and carries a positive charge.
- **Conclusion**: Anilinium ion does not exert a resonance effect.

### Final Answer:
The species that does not exert a resonance effect is **C6H5NH3 (Anilinium ion)**.

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