Which of the following effects are possible in ortho nitrophenol

Options

A. `-l` effect
B. `-R` (mesoeric) effect
C. Intermolecular H - bonding
D. All of these

Answer

To solve the question regarding the possible effects in ortho-nitrophenol, we will analyze the structure and the interactions of the functional groups present in the compound.

### Step-by-Step Solution:

1. **Identify the Structure of Ortho-Nitrophenol:**
- Ortho-nitrophenol consists of a phenolic hydroxyl group (-OH) and a nitro group (-NO2) attached to the benzene ring. The nitro group is positioned ortho (adjacent) to the hydroxyl group.

2. **Negative Inductive Effect (Negative I Effect):**
- The nitro group (-NO2) is highly electronegative and pulls electron density away from the benzene ring through the sigma bonds. This results in a negative inductive effect (I effect) where the electron density is decreased in the ring due to the presence of the nitro group.

3. **Negative Resonance Effect (Negative R Effect):**
- The nitro group also has a resonance effect. It can withdraw electron density from the benzene ring through resonance. This is characterized as a negative resonance effect (R effect) because the nitro group can delocalize the electrons away from the ring, leading to a decrease in electron density in the ring.

4. **Intermolecular Hydrogen Bonding:**
- The hydroxyl group (-OH) can form hydrogen bonds with the nitro group (-NO2) in ortho-nitrophenol. This is possible because the hydrogen atom of the hydroxyl group can interact with the electronegative oxygen atom of the nitro group, leading to intermolecular hydrogen bonding.

5. **Conclusion:**
- All three effects: negative inductive effect, negative resonance effect, and intermolecular hydrogen bonding are possible in ortho-nitrophenol.

### Final Answer:
The possible effects in ortho-nitrophenol are:
1. Negative Inductive Effect (Negative I Effect)
2. Negative Resonance Effect (Negative R Effect)
3. Intermolecular Hydrogen Bonding

Thus, the correct answer is that all three effects are possible.

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