Effect of Freon matrices on the intermediates stabilized in X-ray irradiated 1,7-dioxaspiro[5,5]undecane solutions at 77K

Freon matrices affected the nature of species stabilized upon the X-ray irradiation of frozen 1,7-dioxaspiro[5,5]undecane (DOSU)/CF₃CCl₃ or DOSU/CFCl₃ solutions at 77K. This manifested in the stabilization of a ring-closed DOSU radical cation (RC) with an absorption maximum at ∼440nm in CF₃CCl₃ versus a paramagnetic intermediate with no absorption in this spectral region and a notably different EPR spectrum in CFCl₃. Interestingly, the ultimate product in a sequence of photochemical and thermally induced transformations was the same in both matrices: a distonic DOSU RC with a terminal alkyl fragment afforded upon C–C bond cleavage at the spiro carbon atom.