The stable conformer `(s)` of cis-cyclohexane `1-3-` diol is/are:

Options

A. `1-` axial`-3-` axial form
B. `1-` axial`-3-` equatorial form
C. `1`-equatorial- `3`- axial form
D. `1`- equatorial -`3`- equatorial form

Answer

To determine the stable conformer of cis-cyclohexane 1,3-diol, we will follow these steps:

### Step 1: Understand the Structure of Cis-Cyclohexane 1,3-Diol
Cis-cyclohexane 1,3-diol has two hydroxyl (OH) groups located on the 1st and 3rd carbon atoms of the cyclohexane ring. Since it is a cis isomer, both OH groups are on the same side of the ring.

### Step 2: Identify the Chair Conformation
Cyclohexane predominantly exists in a chair conformation, which minimizes steric strain. In this conformation, the substituents can occupy either axial (up or down) or equatorial (outward) positions.

### Step 3: Position of Hydroxyl Groups
For the cis-1,3-diol, the hydroxyl groups can be placed in either:
- Axial positions (both OH groups pointing up or down)
- Equatorial positions (both OH groups pointing outward)

### Step 4: Analyze Stability
- **Axial Position**: When both OH groups are in axial positions, they can engage in intramolecular hydrogen bonding. This stabilizes the molecule due to the favorable interactions between the hydroxyl groups.
- **Equatorial Position**: If the OH groups are in equatorial positions, they are further apart and do not engage in intramolecular hydrogen bonding, leading to lower stability.

### Step 5: Conclusion
The stable conformer of cis-cyclohexane 1,3-diol is when both hydroxyl groups are in the axial position. This configuration allows for intramolecular hydrogen bonding, which enhances the stability of the molecule.

### Final Answer
The stable conformer(s) of cis-cyclohexane 1,3-diol is/are: **1 axial, 3 axial form.**

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