2-Thio­cytosinium chloride

The title compound (systematic name: 4-amino-2-thioxo-2,3-dihydro­pyrimidin-1-ium chloride), C₄H₆N₃S⁺·Cl⁻, has two cations and two anions in the asymmetric unit. The two cations have nearly the same structure. Both are nearly planar, the largest distance from the non-H atoms to the least-squares plane through the six-membered ring atoms being 0.010 (2) Å. Both Cl⁻ ions serve as hydrogen-bond acceptors. One thiocytosinium cation forms N—H...Cl hydrogen bonds with three Cl⁻ anions and the other one with four Cl⁻ ions, giving a sheet parallel to (101). There is also an N—H...S inter­molecular hydrogen bond.