L-Cysteine-l at 30 K

Abstract

The crystal structure of the orthorhombic phase I of L-cysteine, C 3H7NO2S, has been determined at 30 K. The molecule adopts a gauche+ conformation and the structure consists of zwitterions connected into sinusoidal layers by N-H⋯O hydrogen bonds. Further N-H⋯O 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-H⋯S and S-H⋯O hydrogen bonds. At 30 K the structure is ordered with retention of the S-H⋯S contacts [S⋯S = 3.8489 (4) Å, S-H⋯S = 2.66 (3) Å and S-H⋯S = 150.8 (16)°]. © 2005 International Union of Crystallography Printed in Great Britain - all rights reserved.