Write the structure of the following compound: 3-oxopentanal.

To write the structure of **3-oxopentanal**, we first need to analyze the name and understand the components:

1. **Pentanal**: This indicates that the main chain of the compound is a five-carbon aldehyde. The general formula for an aldehyde is \( RCHO \), where the carbonyl group (\( C=O \)) is at the end of the carbon chain. So, for pentanal, the structure will be:

\[
\text{CH}_3\text{CH}_2\text{CH}_2\text{CHO}
\]

The structure of pentanal is:
\[
\text{CH}_3\text{CH}_2\text{CH}_2\text{C}(=O)\text{H}
\]

2. **3-Oxo**: The term "oxo" refers to a carbonyl group (\( C=O \)). The "3" indicates that this carbonyl group is located on the third carbon of the pentanal chain. Therefore, we need to add a carbonyl group on the third carbon.

Putting it all together, the structure of **3-oxopentanal** will have a carbonyl group on the third carbon, resulting in the following structure:

\[
\begin{array}{c}
\text{CH}_3 - \text{CH}_2 - \text{C}(=O) - \text{CH}_2 - \text{CHO} \\
\text{(3-oxopentanal)}
\end{array}
\]

### Summary
- The main chain is pentanal, with five carbons.
- The oxo group is on the third carbon.
- The final structure is a five-carbon chain with a ketone functional group at the third position and an aldehyde functional group at the terminal position.

### Final Structure
The complete structure is:

\[
\text{CH}_3 - \text{CH}_2 - \text{C}(=O) - \text{CH}_2 - \text{CHO}
\]

This represents 3-oxopentanal correctly.