Interaction of Theophylline with Benzylamine in the Solid State

Abstract

Complexation of theophylline with 4 amines having a benzene moiety was studied in water and in absolute ethanol. Theophylline forms a solid complex with benzylamine in a molar ratio of 1 : 1 from both solvents. However, no solid complex is formed between theophylline and aromatic amines, such as aniline, N-methylaniline, and N, N-dimethyl-aniline. the physico-chemical properties of the complex formed were studied by powder X-ray diffractometry, differential thermogravimetric analysis (DTA-TG), differential scanning calorimeter (DSC) and infrared spectroscopy. The DTA-TG thermograms of the solid complex obtained at a heating rate of 2.5°C/min in air showed that deamination occurred in the temperature range of 53-90°C to yield anhydrous theophylline with two endothermic peaks, a large endothermic peak followed by a broad but small endothermic peak. The reaction was first-order, and the activation energy of determination 29 kcal/mol. The heat of reaction for solid complex formation was estimated to be 21.3 kcal/mol. Hydrogen bonding was the major attractive force between the components of the complex.