Of several photoproducts of 1, 2-cyclohexanedione, the structure of the crystalline compound (IIb) with a molecular formula C12H18O5 was established as perhydro-4a, 9a-epoxydibenzo-p-dioxin-5a, 10a-diol by means of an X-ray crystallographic analysis. In addition, the formation process of this compound was also discussed.
