Acta Cryst. (2005). E61, o2739-o2742  [ doi:10.1107/S1600536805023688 ]

L-Cysteine-I at 30 K

S. A. Moggach, S. J. Clark and S. Parsons

Abstract: The crystal structure of the orthorhombic phase I of L-cysteine, C₃H₇NO₂S, has been determined at 30 K. The molecule adopts a gauche⁺ conformation and the structure consists of zwitterions connected into sinusoidal layers by N-HO hydrogen bonds. Further N-HO hydrogen bonds connect the structure into a three-dimensional array. Under ambient conditions, the thiol H atom is disordered in such a way as to form intermolecular S-HS and S-HO hydrogen bonds. At 30 K the structure is ordered with retention of the S-HS contacts [SS = 3.8489 (4) Å, S-HS = 2.66 (3) Å and S-HS = 150.8 (16)°].

Online 30 July 2005

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