Calcium acamprosate: a triclinic polymorph

The title compound, poly[bis­(μ(3)-4-acetamido­propane­sulfon­ato)­calcium], [Ca(C(5)H(10)NO(4)S)(2)](n), is a triclinic polymorph of the previously reported monoclinic structure [Toffoli et al. (1988 ▶). Acta Cryst. C44, 1493–1494]. The triclinic modification was found to have an all-trans configuration of the acetamido­propane chain, in contrast with the monoclinic polymorph which shows an angle of 74.66 (8)° between the S—C—C—C chain plane and that of the amide group. The Ca(2+) cation is situated on an inversion centre and is hexa­coordinated by six O atoms belonging to different anions in a distorted octa­hedral geometry. This arrangement leads to a layered structure parallel to (011). The layers are held together by N—H⋯O hydrogen bonds and by short C—H⋯O inter­actions, both involving the sulfonate O atoms not coordinated to the Ca(2+) cations. The structure was determined from a crystal twinned by non-merohedry [twin law ([Image: see text]00, 0[Image: see text]0, −0.335 −0.85 1), with a fractional contribution of the minor twin domain of 46.7 (1)%].