Research Article: A hydrogen sulfate salt of chlordiazepoxide

Date Published: July 01, 2012

Publisher: International Union of Crystallography

Author(s): Veronica Diesen, Cláudio Lousada, Andreas Fischer.


Crystals of the hydrogen sulfate salt of chlordiazepoxide (systematic name: 7-chloro-N-methyl-5-phenyl-2,3-dihydro-1H-1,4-benzodiazepin-2-iminium 4-oxide hydrogen sulfate), C16H15ClN3O+·HSO4−, were obtained from a solution of chlordiazepoxide and sulfuric acid in methanol. The structure features chlordiazepoxide mol­ecules that are protonated at the imine N atom. The seven-membered ring adopts a boat conformation with the CH2 group as the prow and the two aryl C atoms as the stern. The dihedral angle between the benzene rings is 72.41 (6)°. In the crystal, the HSO4− anion acts as a bridging group between two chlordiazepoxide cations. The H atom of the protonated imino N forms an N—H⋯O hydrogen bond with a hydrogen sulfate ion. The anion in turn forms two hydrogen bonds, O—H⋯O with the anion as donor and N—H⋯O with the anion as acceptor, to generate an R22(10) loop. Each HSO4− anion connects two chlordiazepoxide moieties of the same chirality.

Partial Text

For general background to benzodiazepines, the structures of two polymorphs of chlordiazepoxide and a chlordiazepoxide dichloro­methane solvate, see: Fischer (2012 ▶) and references therein. For the structure of chlordiazepoxide hydro­chloride, see: Herrnstadt et al. (1979 ▶). For the synthesis of chlordiazepoxide, see: Sternbach et al. (1961 ▶). For acid–base equlibria of chlordiazepoxide and related compounds, see: Yang (1995 ▶). For the graph-set motifs, see: Etter et al. (1990 ▶).




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