DL-cysteinium semioxalate.

Two chiral counterparts (L- and D-cysteinium cations related by an inversion centre) are present in the structure of the title compound, C(3)H(8)NO(2)S(+).C(2)HO(4)(-), with a 1:1 cation-anion ratio. The carboxy group of the cysteinium cation is protonated in the trans position relative to the amino group. The crystal structure is built up of double layers, in which dimers of cysteinium cations are connected to each other not directly, but via bridges of twisted semioxalate anions linked to each other via O-H...O hydrogen bonds forming infinite chains. An interesting feature of the crystal structure is the absence of either S-H...S or S-H...O hydrogen bonds.