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.
|Number of pages||2|
|Journal||Acta Crystallographica Section E: Structure Reports Online|
|Publication status||Published - 15 Jan 2013|