Which of the following molecule has intramolecular `-H` bonding.

Options

A. Hydrogen Fluoride
B. p-nitrophenol
C. o-cresol
D. o-Flourophenol

Explanation

To determine which of the given molecules has intramolecular hydrogen bonding, we need to follow these steps:

### Step 1: Understand Intramolecular Hydrogen Bonding
Intramolecular hydrogen bonding occurs when a hydrogen atom, covalently bonded to an electronegative atom (like oxygen or nitrogen), forms a bond with another electronegative atom within the same molecule. This typically involves a structure that allows the hydrogen to be close enough to the electronegative atom to form a bond.

**Hint:** Look for molecules where a hydrogen atom is bonded to an electronegative atom and is in proximity to another electronegative atom within the same molecule.

### Step 2: Identify the Candidate Molecules
We need to analyze the structures of the given molecules to see if they can form intramolecular hydrogen bonds. The candidates are:
1. Hydrogen fluoride (HF)
2. Paranitrophenol
3. Orthocresol
4. Ortho-fluorophenol

**Hint:** Draw the structures of each molecule to visualize the potential hydrogen bonding interactions.

### Step 3: Analyze Each Molecule
1. **Hydrogen Fluoride (HF)**: This molecule exhibits intermolecular hydrogen bonding, as it forms hydrogen bonds between different HF molecules. Therefore, it does not have intramolecular hydrogen bonding.

**Hint:** Remember that intramolecular bonding occurs within a single molecule, not between different molecules.

2. **Paranitrophenol**: In this molecule, the hydroxyl (–OH) group and the nitro (–NO2) group are located on opposite ends of the benzene ring. The distance between these groups is too large for intramolecular hydrogen bonding to occur.

**Hint:** Check the positions of functional groups; they must be close enough to interact.

3. **Orthocresol**: This molecule has a hydroxyl (–OH) group and a methyl (–CH3) group. However, the methyl group does not have the capability to accept hydrogen bonding, as it lacks a highly electronegative atom.

**Hint:** Identify if there are any electronegative atoms that can act as hydrogen bond acceptors.

4. **Ortho-fluorophenol**: In this molecule, the hydroxyl (–OH) group is adjacent to the fluorine atom on the benzene ring. The hydrogen from the hydroxyl group can form a hydrogen bond with the fluorine atom, making it a candidate for intramolecular hydrogen bonding.

**Hint:** Look for proximity of electronegative atoms that can facilitate bonding.

### Step 4: Conclusion
After analyzing all the candidates, we find that **ortho-fluorophenol** is the only molecule that exhibits intramolecular hydrogen bonding due to the close proximity of the hydroxyl group and the fluorine atom.

**Final Answer:** The molecule with intramolecular hydrogen bonding is **ortho-fluorophenol**.