Detection of trimethylenemethane by IR spectroscopy:result of the photoisomerization of methylenecyclopropane in a halogen-doped xenon matrix Original Research Article

Upon irradiation in a halogen-doped xenon matrix at 10 K, methylenecyclopropane (5) undergoes a ring opening and trimethylenemethane (2) is formed. The identity of 2 is not only proven by its ESR spectrum, but under the specific conditions mentioned above, the concentration of 2 is high enough to also allow the observation of its IR spectrum. Comparison of the experimental IR spectra of 2 and several of its deuterated isotopomers with calculated (UMP2/6-31G∗) vibrational spectra provides additional evidence for its structure. Changing the wavelength allows the photochemical backformation of 5 from 2. On warm-up 2, as expected for a triplet molecule, dimerizes yielding 1,4-dimethylenecyclohexane.