Pseudosymmetry with Z '=4 in 1,3-propanesultone at 100 K

The asymmetric unit of the low-melting title compound, C3H6O3S, contains fo ur molecules at low temperature. The conformations of two of the five-membe red rings are envelopes, one has the half-chair conformation, and the fourt h is intermediate between an envelope and a half-chair. S=O distances range from 1.424(2) to 1.436(2) Angstrom, S-O distances from 1.582(2) to 1.587(2 ) Angstrom, and S-C distances from 1.760(3) to 1.776 (3) Angstrom. The crys tal structure contains approximate centers, 2(1) screw axes, and translatio ns. Above 180 K, the compound exists as a polymorph in which these symmetry operations are exact, and Z' = 1.