Which one following is the most stable conformer ?

Options

A.
B.
C.
D.

Answer

To determine the most stable conformer among the given options, we will analyze the conformers based on steric interactions and hydrogen bonding. Here’s a step-by-step solution:

### Step 1: Identify the Conformers
We have four options (A, B, C, and D) representing different conformations of a molecule. Each option has a different arrangement of functional groups (like CH3 and OH) around a central bond.

### Step 2: Analyze Each Conformer
- **Option A**:
- Arrangement: CH3 - OH - H (on one side) and CH3 - OH - H (on the opposite side).
- Stability: This arrangement minimizes steric hindrance between the bulky CH3 groups. However, there is no hydrogen bonding present.

- **Option B**:
- Arrangement: H - H - H (on one side) and CH3 - CH3 (on the opposite side).
- Stability: This conformer has CH3 groups close to each other, leading to steric repulsion. This makes it less stable.

- **Option C**:
- Arrangement: CH3 - OH (on one side) and CH3 - H (on the opposite side).
- Stability: This arrangement allows for hydrogen bonding between the OH group and a hydrogen atom, which stabilizes the conformer. The CH3 groups are also positioned opposite each other, reducing steric hindrance.

- **Option D**:
- Arrangement: OH - H - H (on one side) and CH3 - CH3 (on the opposite side).
- Stability: Similar to option B, there is steric repulsion between the CH3 groups, and the OH group does not participate in effective hydrogen bonding due to the proximity of the other hydrogen atoms.

### Step 3: Compare Stability
- **Most Stable**: Option C is the most stable conformer due to the presence of hydrogen bonding and minimized steric hindrance.
- **Next Stable**: Option A, as it has minimized steric interactions.
- **Least Stable**: Options B and D due to steric repulsion between CH3 groups.

### Conclusion
The most stable conformer is **Option C**.

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