Redetermined crystal structure of ß-dl-me-thio-nine at 320†K.

The structure of ß-dl-me-thio-nine, C5H11NO2S, in the space group C2/c, is here confirmed to be fully ordered all the way up to the phase transition at approximately 326 K, where displacive sliding of mol-ecular bilayers gives the disordered P21/c α form [data at 340 K; Görbitz (2014). Acta Cryst. E70, 341-343]. The geometry of hydrogen bonds in LD-LD hydrogen-bonding patterns [Görbitz et al. (2009). Acta Cryst. B65, 393-400] at the hydro-philic core of each mol-ecular bilayer are virtually unperturbed by the phase shift, but the C-C-S-C torsion angle of the side chain changes from trans at 320 K to gauche+ for the major conformation at 340 K.