Abstract
The interaction of sulfonamides with 18-crown-6 (1, 4, 7, 10, 13, 16-hexaoxacyclooctadecane) was studied, observing the effect on the solubility of sulfonamides in organic solvents. In benzene solution, sulfamonomethoxine and sulfamethoxazole formed the respective crystalline complexes with 18-crown-6. The stability constant K for sulfamonomethoxine/18-crown-6 system was particularly large in comparison with the other systems. In chloroform solution, however, the solid complex was not obtained in any systems. K values in chloroform were smaller than those in benzene. Furthermore, when the complex formation of sulfamethomidine with 18-crown-6 was investigated in various dielectric constants of solvents, K value decreased with the increase in polarity of the solvent. These results indicated that the hydrogen bonding might be a primary force of the formation of these complexes. Additionally, the complex formation in solid phase was confirmed in sulfamonomethoxine/18-crown-6 and sulfamethoxazole/18-crown-6 systems by powder X-ray diffractometry and differential scanning calorimetry. From infra-red and nuclear magnetic resonance spectra, it was suggested that 4-amino group of sulfonamide might interact with the oxygen of ether ring of 18-crown-6.
