ORGANIC CHEMISTRY Chapter 13 3.9B Absorption Maxima for Nonconjugated and Conjugated dienes o alkenes and nonconjugated dienes usually have absorption maxima below 200 nm o Compounds whose molecules contain conjugated multiple bonds have absorption maxima at wavelengths longer than 200 nm o When a molecule absorbs light at its longest wavelength, an electron is excited from its HOMO to the Lumo Department of Chemistry, Xiamen UniversityORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 13 13.9B Absorption Maxima for Nonconjugated and Conjugated Dienes Alkenes and nonconjugated dienes usually have absorption maxima below 200 nm. Compounds whose molecules contain conjugated multiple bonds have absorption maxima at wavelengths longer than 200 nm. When a molecule absorbs light at its longest wavelength, an electron is excited from its HOMO to the LUMO