Preparation, Characterization, Hirshfeld surface, Reduced density gradient analysis and transformation of 2,4-dinitroanisole with different crystal forms

Abstract

The 2,4-dinitroanisole (DNAN) is the new liquid phase carrier used widely in the melt cast explosive. DNAN has two crystal forms and there is relatively little research on two crystal forms. In this article α-DNAN and β-DNAN are prepared by cooling crystallization methods with different cooling rates and subjected to HPLC, IR, DSC, morphology and x-ray single crystal diffraction analysis. The ΔHm of β-DNAN is 17.651 kJ·mol−1 and the ΔHm of α-DNAN is 20.758 kJ·mol−1. According to Hirshfeld surface analysis, β-DNAN has 15.3 % O∙∙∙O contacts and 54.5 % O∙∙∙H contacts, while α-DNAN has 10.6 % O∙∙∙O contacts and 61.8 % O∙∙∙H contacts. The enrichment ratios for all contacts of α-DNAN and β-DNAN are calculated. The total interaction energy from energy framework of β-DNAN and α-DNAN are -107.9 kJ·mol−1 and -201.2 kJ·mol−1. The red color representing steric repulsive interactions is the same and the green color representing van der Waals interactions is different according to RDG analysis of α-DNAN and β-DNAN. From above four perspectives, it been proven that α-DNAN is more batter thermal stability than β-DNAN. The solvent non-solvent method can achieve α-DNAN transformation into β-DNAN. The β-DNAN transformation into α-DNAN is studied at 313.15 K, 323.15 K and 333.15 K. Comparing the two crystal transformation processes, α-DNAN transformation into β-DNAN is difficult, while β-DNAN transformation into α-DNAN is easy to achieve. This indicate crystal stability of β-DNAN is poor, while crystal stability of α-DNAN is good.