4-Hydroxypyridinium-3-sulfonate

The reaction of 4-hydroxypyridine and oleum produces 4-hydroxypyridinium-3-sulfonate, C5H5NO4S, which shows delocalized bonds in the six-membered ring. In the crystal, adjacent zwitterions are linked by N—H...O and O—H...O hydrogen bonds into a layer motif. The crystal studied was a racemic twin.