The vibrational and electronic spectra of 3,4-dimethylenecyclobutene

The infrared spectrum of 3,4-dimethylenecyclobutene (dmcb) as a vapour, glass, and polycrystalline film has been investigated from 4000 to 250 cm-1. The Raman spectrum of liquid dmcb and the infrared spectrum of 1,2-dideutero-3,4-dimethylenecyclobutene vapour have also been investigated. On the basis of these results a partial assignment of the spectrum has been made. A study of the electronic spectrum of dmcb from the visible to the vacuum ultraviolet at 169 nm has also been undertaken and the spectrum has been found to be very diffuse in all bands. Assignments are discussed in the light of theoretical calculations.