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 C 2/ 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 P 2 1 / c α form [data at 340 K; Görbitz (2014). Acta Cryst. E 70 , 341–343]. The geometry of hydrogen bonds in LD–LD hydrogen-bonding patterns [Görbitz et al. (2009). Acta Cryst. B 65 , 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.