Knowledge Bank

We have observed the optical spectra of the series of endocyclic olefins: cis-2-butene, cyclopropene, cyclobutene, and cyclopentene. These electronic spectra are plots of absolute cross section vs. frequency over the range of 45 000 $cm-1$ to 90 000 $cm-1$. We have also studied the ultraviolet photoelectron spectrum of these substances. A discussion of these results and of the electronic energy levels of olefins will be presented in light of ab intitio molecular orbital calculations.