Intra-molecular H-bonding is possible in which of the following.

Options

A. 1. cis-cyclohexane-1,2-diol
B. 2. trans-cyclohexane-1,2-diol
C. 3. cis-cyclohexane-1,3-diol
D. 4. cis-cyclohexane-1,4-diol

Explanation

To determine which of the given compounds exhibits intramolecular hydrogen bonding, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Identify the Compounds**: We have four compounds to analyze:
- (A) Cis-cyclohexene 1,2-diol
- (B) Trans-cyclohexene 1,2-diol
- (C) Cis-cyclohexene 1,3-diol
- (D) Cis-cyclohexene 1,4-diol

2. **Draw the Structures**:
- **(A) Cis-cyclohexene 1,2-diol**: Both hydroxyl (–OH) groups are on the same side of the cyclohexene ring, allowing them to be close enough for hydrogen bonding.
- **(B) Trans-cyclohexene 1,2-diol**: One hydroxyl group is above the plane and the other is below, which increases the distance between them, making hydrogen bonding less favorable.
- **(C) Cis-cyclohexene 1,3-diol**: The hydroxyl groups are on the same side but are separated by one carbon, which increases the distance and reduces the likelihood of hydrogen bonding.
- **(D) Cis-cyclohexene 1,4-diol**: The hydroxyl groups are on opposite sides of the cyclohexene ring, which significantly increases the distance, making hydrogen bonding improbable.

3. **Evaluate Intramolecular Hydrogen Bonding**:
- **(A) Cis-cyclohexene 1,2-diol**: The close proximity of the two –OH groups allows for strong intramolecular hydrogen bonding.
- **(B) Trans-cyclohexene 1,2-diol**: The distance between the –OH groups is too great for effective hydrogen bonding.
- **(C) Cis-cyclohexene 1,3-diol**: The distance is also too great for effective hydrogen bonding.
- **(D) Cis-cyclohexene 1,4-diol**: The distance is the greatest, making hydrogen bonding impossible.

4. **Conclusion**: The only compound that exhibits intramolecular hydrogen bonding is **(A) Cis-cyclohexene 1,2-diol**.

### Final Answer:
**Intra-molecular H-bonding is possible in: (A) Cis-cyclohexene 1,2-diol.**