Draw the most stable conformer of 3-hydroxypropanal.

Answer

To draw the most stable conformer of 3-hydroxypropanal, we will follow these steps:

### Step 1: Identify the Structure of 3-Hydroxypropanal
3-Hydroxypropanal has the following structure:
- It contains a propanal backbone with a hydroxyl (-OH) group attached to the third carbon.
- The molecular formula can be represented as:
\[ \text{H}_2\text{C}=\text{O}-\text{CH}_2-\text{CH}(\text{OH})-\text{H} \]
- The aldehyde group is at carbon 1, and the hydroxyl group is at carbon 3.

### Step 2: Draw the Fischer Projection
In the Fischer projection, we can represent the molecule as follows:
```
H OH
\ /
C
/ \
H C=O
/ \
H H
```
Here, the aldehyde group (C=O) is at the top, and the hydroxyl group (OH) is on the left.

### Step 3: Convert to Newman Projection
To analyze the conformers, we need to look at the molecule from a Newman projection perspective. We will look down the bond between the first carbon (C1) and the second carbon (C2):
- C1 has the aldehyde group and two hydrogens.
- C2 has the hydroxyl group, one hydrogen, and is connected to C3.

### Step 4: Draw the Eclipsed and Staggered Conformers
- **Eclipsed Conformer**: In this conformer, the groups on C1 and C2 are aligned, which leads to steric strain.
- **Staggered Conformer**: In this conformer, the groups are staggered, minimizing steric interactions.

### Step 5: Identify Hydrogen Bonding
In the staggered conformer, the hydroxyl group (OH) can form a hydrogen bond with one of the hydrogen atoms on C2. This interaction stabilizes the molecule:
- The hydrogen bond occurs between the oxygen (δ-) of the hydroxyl group and the hydrogen (δ+) on the adjacent carbon.

### Step 6: Conclusion
The most stable conformer of 3-hydroxypropanal is the staggered conformer where the hydroxyl group can participate in hydrogen bonding with the hydrogen atom on the adjacent carbon. This interaction reduces steric strain and increases stability.

### Final Structure
The most stable conformer can be represented as:
```
H OH
\ /
C
/ \
H C=O
/ \
H H
```