DETECTION OF TRIMETHYLENEMETHANE BY IR SPECTROSCOPY - RESULT OF THE PHOTOISOMERIZATION OF METHYLENECYCLOPROPANE IN A HALOGEN-DOPED XENON MATRIX

Upon irradiation in a halogen-doped xenon matrix at 10 K, methylenecyc lopropane (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. Compa rison of the experimental IR spectra of 2 and several of its deuterate d isotopomers with calculated (UMP2/6-31G) vibrational spectra provid es additional evidence for its structure. Changing the wavelength allo ws the photochemical backformation of 5 from 2. On warm-up 2, as expec ted for a triplet molecule, dimerizes yielding 1,4-dimethylenecyclohex ane.