• Varadharajan, Krishnakumar
• Louhi-Kultanen, Marjatta

Abstract

<p>The presence of superstructure and impact of solvent on the formation of different forms in the simple trimorphic system of 6-chloro-2,4-dinitroaniline (CDA) are investigated in this report. The experiment was carried out as part of sorting three forms of CDA. Forms I and III were obtained by an anti-solvent precipitation method. The filtrate, i.e. the mother liquor obtained from anti-solvent precipitation, was further used in a slow evaporative crystallization experiment. This evaporation method yielded superstructures on form I crystals in acetone (primary solvent) and water (secondary solvent). The obtained results showed that superstructures on form I resulted from combining anti-solvent crystallization and slow evaporative crystallization. Reprecipitation was carried out to verify the observed superstructure on form I using different volume fractions of water. Furthermore, the superstructure was observed in slow evaporation of CDA solution in an acetone-water mixture. The solubility data were measured for CDA in pure acetone, ethyl acetate (EtOAc), dichloromethane (CH₂Cl₂) and methyl tert-butyl ether (MTBE), and binary acetone-water, CH₂Cl₂-MTBE, EtOAc-MTBE solvent mixtures at 293 K and 298 K. X-ray powder diffraction study confirmed the formation of different forms and recorded SEM images laid a foundation for understanding the origin of the superstructure. The functional group vibrations and packing difference between form I and form III were clearly identified from the FTIR spectra. The UV-Vis-NIR results confirmed the interaction between water and solute in solution. Based on the solvent parameters and SEM images, the formation of the superstructure was hypothesized. This journal is</p>

Topics

• impedance spectroscopy
• scanning electron microscopy
• experiment
• precipitation
• crystallization
• evaporation