E. Shefter
Jun 1, 1969
Citations
0
Influential Citations
18
Citations
Journal
Journal of pharmaceutical sciences
Abstract
Single crystal X-ray diffraction methods were utilized in obtaining the crystal and molecular structure of a 1:1 association complex between 5-chlorosalicylic acid and theophylline. The crystals are monoclinic (space group P 21/c) with cell parameters of a = 7.845 A b = 9.636 A c = 21.185 A and β = 92.20° The crystals contain a significant fraction of the impurities 3,5-dichloro- and 3-chlorosalicylic acid. Hydrogen bonds are the major attractive forces between the components of the complex. A relatively strong hydrogen bond exists between the carboxyl group of 5-chlorosalicylic acid and N(9) of theophylline (2.682 A.). The theophylline molecules are in a dimeric arrangement by virtue of centrosymmetrically related hydrogen bonds between N(7) and TO(10). The packing arrangement of the molecules suggests that the stacking forces are similar to those in a caffeine: 5-chlorosalicylic acid complex.