Redetermined crystal structure of β-dl-me­thio­nine at 320 K

The structure of β-dl-me­thio­nine, C(5)H(11)NO(2)S, 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 mol­ecular bilayers gives the disordered P2(1)/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 hydro­philic core of each mol­ecular 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.