metal-organic compounds
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Potassium (1R,4R,5S,8S)-4,5,8-trihydroxy-3-oxo-2,6-dioxabicyclo[3.3.0]octane-4-sulfonate dihydrate
The title salt, K+·C6H7O9S-·2H2O, formed by reaction of dehydro-L-ascorbic acid with potassium hydrogen sulfite in water, crystallizes as colourless plates. The potassium ion is coordinated by eight O atoms arising from hydroxy or sulfonate groups. The sulfonate group is bonded to the C atom neighbouring that of the lactone carbonyl group. As is commonly observed in crystalline L-ascorbic acid derivatives, the O atom of the primary hydroxy group is linked to the second C atom from the lactone C atom, forming a hemi-acetal function, thereby creating a bicyclic system of two fused five-membered rings, both of which have envelope conformations with one of the shared C atoms as the flap. Addition of the sulfur nucleophile occurs from the less hindered face. One of the two independent lattice water molecules has hydrogen bonds to sulfonate O atoms of two different anions and is the acceptor of bonds from hydroxy groups of two further anions; the second lattice water molecule donates to the carbonyl and a hydroxy O atom in different anions, and accepts from a hydroxy O atom in a further anion. Thus, through K-O coordination and hydrogen bonds, the potassium cations, sulfonate anions and water molecules are linked in a three-dimensional network.
organic compounds
Open access
The title compound, C7H8N2O2, formed by dehydration of the corresponding dicarboxamide, crystallizes as rectangular prisms. The molecules have a C2 axis of symmetry through the C atom bearing the methyl groups and the mid-point of the ring C—C bond, and the 1,3-dioxolane ring adopts the extreme twist conformation of the two possible with this symmetry. This brings the two nitrile groups nearest to a linear arrangement when the molecule is viewed along the ring C—C bond. The correct absolute configuration of the molecule was defined by that of the original starting material, (2R,3R)-tartaric acid. The packing is largely controlled by a number of C—HN interactions.