ИСТИНА

The equilibrium structure of izoniazid, also known as isonicotinylhydrazide (INH), an antibiotic used for the treatment of tuberculosis, has been determined for the first time by means of gas electron diffraction (GED) and quantum chemical calculations. The equilibrium structural parameters were obtained, the disagreement factor was 3.6%. The gas phase structure of INH is different from that in the solid phase due to the effect of intermolecular hydrogen bonding in the crystal. Sulfanilamide (SA) is a sulfonamide antibacterial. According to a number of quantum chemical calculations SA can adopt four conformations with different orientation of the two amino groups. The calculations predict the two conformers with the amino group eclipsing the SO2 group to be predominant in the gas phase. According to GED at a temperature of 180(5) °C the vapor over the solid SA consists of the eclipsed conformers. The GED intensities, however, possess a very low sensitivity toward the vapor composition due to a weak sensitivity of GED to the positions of hydrogens.