Mercury(3p,) Sensitized Photoreactions of Furan: Details of the Primary Processes

INTRODUCTION In earlier studies"2 of the photosensitization of furan vapour by mercury(3P1) atoms, it has been reported that the principal photochemical process is a clecarbonylation which has a quantum yield of 04 at a pressure of furan of a few mm Hg. The C3 fragment which was simultaneously produced was found to consist of a mixture of cyclopropene and methylacetylene. At high conversions, some allene was also formed presumably by a secondary process. A study2 of the minor products formed in this system, especially at I atm pressure, indicated that on sensitization by Hg(3P,) atoms furan was capable of undergoing Diels—Alder addition with quantum yields of the order of a few per cent, and that the adducts corresponded to (I), (II), and (III). The identification of (III), which is the Diels—Alder adduct of furan to