2,3-Benzoquino[15]crown-5

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.

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