To distinguish between 1,3-butadiene and butanone using UV spectroscopy, it is essential to understand their molecular structures and the types of electronic transitions that occur in each compound.

1. Molecular Structure
- **1,3-Butadiene**: A conjugated diene with the structure CH2=CH-CH=CH2.
- **Butanone**: A ketone with the structure CH3-CO-CH2-CH3.

2. UV Absorption Characteristics
- **1,3-Butadiene**:
- Exhibits π to π* transitions due to its conjugated double bonds.
- Absorbs UV light typically in the range of 190-210 nm.
- The conjugation enhances the intensity of the absorption bands.
- **Butanone**:
- Displays n to π* transitions because of the carbonyl (C=O) group.
- Absorbs UV light in the range of 280-300 nm.
- The presence of the carbonyl group results in a distinct absorption that is not present in 1,3-butadiene.

3. UV Spectra Analysis
- **Distinct Peaks**:
- When running UV spectra for both compounds, look for distinct peaks:
- **1,3-Butadiene** will show peaks in the lower wavelength range (190-210 nm).
- **Butanone** will show peaks in the higher wavelength range (280-300 nm).
- **Conclusion**:
- By analyzing the wavelengths of maximum absorbance, you can effectively distinguish between 1,3-butadiene and butanone. The presence of conjugation and the type of functional groups lead to significantly different UV absorption profiles.