Study On Polymorphs, Crystal Structure Determination And Rystal Habits For P-Methbylacetanilide

In medicine and materials field, there is a growing concern over the monitoring andcontrol of the polymorphs. The polymorphs that appear in the process not only depend on themolecular structures, but also the operating factors. In this paper, using a combination ofexperiment, characterization and molecular dynamics simulation, the polymorph structuresand the effect of micro-environment on crystal growth for a model compound, i.e.p-Methylacetanilide (PMAA), is investigated.Polymorphisms of PMAA are formed in different solvents, and it suggested that thepolymorphs are influenced by solvents. The selected point charge calculation methodand force field methods is used to optimize the structure of the PMAA molecules, the lowestenergy molecular conformation is chosen as the initial structure for structure prediction withthe Polymorph Predictor module in Materials Studio software. It is found that two predictedlowest energy structures are coincided well with the referred polymorphisms, and thecalculating XPRD is also coincided well with the experimental XPRD.The basic properties of the PMAA and its polymorphs were studied. Further experimentsindicate that it is easy to form mixed crystals of the two polymorphs during antisolventcrystallization, where DMF or ethanol is selected as solvent, and water asantisolvent. The solution structure of the different solvent systems is simulated by moleculardynamics method. The radial distribution functions of the solute-solute molecules, solute-solvent molecules are analyzed; the results show that PNA21polymorphism is prone to formin DMF and ethanol for its stronger interaction with PMAA.