Acta Cryst. (2009). E65, o1291-o1292  [ doi:10.1107/S1600536809017322 ]

Redetermination of L-tryptophan hydrobromide

K. Stewart

Abstract: The redetermined crystal structure of the title compound, C₁₁H₁₃N₂O₂⁺·Br^-, is reported. Data collection at 100 K about three crystallographic axes resulted in a crystal structure with significantly higher precision in comparison to the two-dimensional data collected at 176 K [Takigawa et al. [(1966) Bull. Chem. Soc. Jpn, 39, 2369-2378]. The carboxyl group and indole ring system are planar, with maximum deviations of 0.002 (2) and 0.007 (2) Å, respectively, and make an angle of 70.17 (1)° with each other. The molecules are arranged in double layers of carboxyl and amino groups parallel to the ab plane, stabilized by an extensive network of N-HBr and O-HBr hydrogen bonds. The polar layer is held together by a network of three N-HBr hydrogen bonds and one O-HBr hydrogen bond. In the non-polar layer, the indole rings are linked mainly by electrostatic N-HC interactions between the polarized bond N-H (H is ⁺) of the pyrrole unit and two of the ring C atoms (^-) of the benzene rings of adjacent molecules. The distances of these electrostatic interactions are 2.57 and 2.68 Å, respectively. C-HO and C-H interactions are also present.

Online 14 May 2009

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