Carbonyl <i>O</i>‐Oxides and Dioxiranes: The Influence of Substituents on Spectroscopic Properties

Abstract

Abstract Triplet 4‐oxocyclohexadienylidenes 6 , matrix‐isolated in Ar/ 2% O 2 at 10 K, react with triplet O 2 on annealing the matrix. Primary reaction products are quinone oxides 4 , which have been characterized by IR and UV/Vis spectrometry. They are very photolabile; long‐wavelength irradiation converts them into spiro‐dioxiranes 5 , which in turn yield lactones 10 upon irradiation with visible light. Experimental data have been obtained for quinone oxides 4a–g ; additionally, ground‐state properties and UV/Vis absorptions of quinone oxides 4a,b and 4e–1 have been calculated by the MINDO‐3/UHF and CNDO/S methods. Since the theoretical and experimental maxima of the π → π * transitions are in good agreement, we conclude that our semiempirical calculations give an adequate picture of quinone oxides 4 which may best be described as dipolar diradicals.