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Crystal structure of four solvates of lorazepam with ethanol (A), acetone (B), dioxane (C) and cyclohexanone (D)

X-ray structure analysis of four solvates of lorazepam with ethanol (A), acetone (B), dioxane (C) and cyclohexanone (D) is described. All four crystallize in the triclinic system, space group P1, and with the lorazepam molecules of essentially the same conformation. As common in other benzodiazepines, the seven- membered rings adopt a boat conformation. The four solvates have different kinds of hydrogen bonding. While in (A), (B) and (D) lorazepam molecules are interconnected either by N-H...O (282 to 292 pm) or O-H...O hydrogen bonds (289 pm) in (C) such bonding does not exist. The solvent molecules fill cavities in the crystal structures and are linked to the lorazepam molecules either by van der Waals interactions as in (A), (B) and (C) or by hydrogen bond of the O-H...O type of 281 pm in (D). The investigated structures are compared with other lorazepam derivatives and solvates previously described in the literature.

lorazepam, solvates, crystal structure

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