X-RAY STRUCTURAL STUDIES AND PHYSICOCHEMICAL CHARACTERIZATION OF THE 1-BUTANOL, 1-PENTANOL, AND 1,4-DIOXANE SOLVATES OF SUCCINYLSULFATHIAZOLE

The crystal structures and thermal decomposition of three solvated for ms of the antibacterial drug succinylsulfathiazole (SST) have been stu died. The solvates, with 1:1 host-guest stoichiometry, are SST.1-butan ol (1) SST.1-pentanol (2), and SST.1,4-dioxane (3). Solvates 1 and 2 c rystallize in the triclinic system, space group P1, with two formula u nits per cell, and are nearly isostructural. The OH groups of the gues t molecules in both solvates engage in hydrogen bonding to the host SS T and occupy cavities in the crystals. Solvate 3 is triclinic, space g roup P1, with two formula units per cell, but the two independent solv ent molecules are located in crystallographically distinct channels. I n one channel, solvent molecules are hydrogen bonded to the host while , in the other, they are held by van der Waals interactions only. The structural results are in accord with thermogravimetric and differenti al scanning calorimetric data which indicate one-step desolvation for 1 and 2 but two-step desolvation for 3. X-ray powder diffraction was u sed to attempt identification of the polymorphic forms of SST resultin g from desolvation of 1-3. Desolvation of 1 and 3 appears to yield pur e polymorphs of SST while 2 yields a mixture of polymorphs. The activa tion energies for the desolvation of the nearly isomorphous solvates 1 and 2 were found by dynamic thermogravimetry to be 155 and 149 kJ mol (-1), respectively.