Which of the following conformers for ethylene glycol is the most stable?

Options

A.
B.
C.
D.

Explanation

To determine which conformer of ethylene glycol is the most stable, we need to analyze the different conformers provided (A, B, C, and D) and identify the one that exhibits the most favorable interactions, particularly intramolecular hydrogen bonding.

### Step-by-Step Solution:

1. **Identify the Conformers**:
- We have four conformers to consider: A, B, C, and D. Each conformer has a different spatial arrangement of atoms.

2. **Draw the Structures**:
- For each conformer, draw the molecular structure to visualize the arrangement of hydroxyl (OH) groups and hydrogen (H) atoms.

3. **Analyze Intermolecular and Intramolecular Interactions**:
- Look for hydrogen bonding interactions. Intramolecular hydrogen bonding occurs when a hydrogen atom bonded to an electronegative atom (like oxygen) interacts with another electronegative atom within the same molecule.

4. **Focus on Conformer D**:
- In conformer D, there is a significant intramolecular hydrogen bond formed between one of the hydroxyl groups (OH) and a hydrogen atom (H) that is part of the ethylene glycol structure. This interaction stabilizes the molecule.

5. **Compare with Other Conformers**:
- Check the other conformers (A, B, and C) for similar intramolecular hydrogen bonding. If they lack such interactions or have less favorable arrangements, they will be less stable compared to conformer D.

6. **Conclusion**:
- Since conformer D exhibits intramolecular hydrogen bonding, it is the most stable conformer of ethylene glycol among the options provided.

### Final Answer:
The most stable conformer of ethylene glycol is **D** due to the presence of intramolecular hydrogen bonding.