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organic compounds
The X-ray structure analysis of the title compound, 2,5,8,11,14-pentaoxabicyclo[13.4.0]nonadeca-15(1),17-diene-16,19-dione, C14H18O7, reveals that the fused quinone causes a significant deformation of the crown ring from the expected rectangular form, because of the serious steric repulsion between the two carbonyl groups and the two adjacent OCH2CH2 units. One of these units deviates significantly from the mean plane of the quinone, while the other bends inward, remaining coplanar with the quinone. Such a constrained and folded structure is reflected in the abnormal sp2 bond angles (110 and 130°) of one of the bridgehead quinonoid C atoms.