Reactions of cyclopropane and propene in the condensed phase have been induced and monitored simultaneously using a conventional high-resolution electron energy loss spectrometer. Reaction products are identified from both the vibrational and the electronic spectra of the irradiated solid samples. Propene is identified as the major initial reaction product from its characteristic vibrational bands. Subsequent reactions are shown to lead to the formation of longer chains. Some of these chains contain conjugated diene units. This latter product cannot be the result of standard oligomerization reaction steps following the formation of primary radicals by dissociative processes alone. Subsequent collision processes leading to additional H abstraction must be invoked to explain the formation of the diene units.