A hydrogen sulfate salt of chlordiazepoxide

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), C(16)H(15)ClN(3)O(+)·HSO(4) (−), 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 CH(2) 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 HSO(4) (−) 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 R (2) (2)(10) loop. Each HSO(4) (−) anion connects two chlordiazepoxide moieties of the same chirality.