Disodium rhodizonate: a powder diffraction study

The crystal structure of the title compound, disodium 1,2,3,4-tetra­oxo-5-cyclo­hexene-5,6-diolate, 2Na⁺·C₆O₆^2-, is built up of alternating layers of hexa­gonally packed Na⁺ cations and rhodizonate dianions. The rhodizon­ate dianion has a slightly twisted conformation.

1,4,7,10,13,16-Hexaoxacyclo­octa­decane–ammonia (1/2)

The title compound, a 1:2 adduct of 18-crown-6 and ammonia, C₁₂H₂₄O₆·2NH₃, has inversion symmetry. Two ammonia mol­ecules are connected to the crown ether above and below the cyclic plane via N—H...O hydrogen bonds to form a disc-like adduct.