A Study Of Solution Thermodynamics?polymorphism And Habit Of 1,3-dimethylurea

1,3-dimethylurea(DMU)is an intermediate for synthesizing theophylline and caffeine,also it is widely used in pharmaceutical and food industry.So far the researches of DMU focus on its synthetic process,although there has been report about its polymorphism phenomenon,there has been no systematic research about its crystal thermodynamics and habit.This paper study the solution thermodynamics of DMU,as well as the modification of its polymorph and crystal habit.This dissertation addresses the solubility of DMU in fifteen different solvents using dynamic laser method,and the solubility data are correlated as well.Based on the above analysis,thermodynamic properties are calculated as the theoretical basis for the afterwards cooling crystallization.The solubility line shows that the solubility of DMU increases as the temperature increases,thus the dissolving process is endothermic.Using the Liner Solvation Energy relationship to explain the dissolving process,the result shows that the interactions between the solute and the solvent promote the dissolution of the solute in the solvent.To further explain the dissolving mechanism of DMU,this paper adopts COSMORS software to calculate the interaction energy of solute-solvent and solvent-solvent.The results confirmed the stronger interaction between solute and solvent leads to the higher solubility.Among all the interaction,the hydrogen bonding between solvent and solute contribute the most to the interaction energy.Besides,the solubility values of DMU in the selected solvents are predicted by COSMO-RS which show a good agreement with the measured values.Finally,this dissertation take s an attempt to obtain the desirable polymorph and morphology of DMU by cooling crystallization.The result shows that crystal form I can be gotten at higher temperature(about above 30?)while form II can be gotten at comparatively lower temperature(about bellow 30?).Also the influence of solvent on DMU crystal habit was studied and it is found that aspect ratio of final products decrease as the polarity of solvent increases,and products show better mobility.Thus,we can get satisfied products by modify the solvent system.There has no related report about above research.