a The supramolecular structure of 3-amino-4-halo-5-methylisoxazoles (with halo = Cl, Br, I) was investigated in order to suggest a route for crystallization of small molecules. The hierarchy of intermolecular interactions during the growth of the crystal was established by x-ray diffraction, 1 H NMR titration, QTAIM analysis and quantum mechanical calculations. The relationship between QTAIM and energetic data was the fundamental innovation in this work. It allowed the partitioning of the dimer interaction energy between interacting atoms. Partitioning shows the cooperation of intermolecular interactions in the stabilization of dimers and led to observation of the energetic consequences that small changes in the molecular structure of each compound may have on the crystal packing. The proposed route for crystallization of the supramolecular cluster was based on the energetic hierarchy, in which the hydrogen bond is the strongest interaction and the first to form, and the π-interactions are weaker than the hydrogen bond and cannot compete with it. However, the πinteractions are responsible for the growth of the crystal connecting the rising layers of the hydrogen bond dimers. The other interaction formed, the halogen bond, is too weak to compete with the other two interactions, but it is fundamental for linking the layer that leads to the final three-dimensional arrangement. Finally, a new way of understanding the crystallization process and the design of new materials is presented. 11-13Our objective herein is to further our study of the analysis of the crystal packing of heterocycles, taking into account consequences arising from small changes in molecular

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This work investigated the chemical and mechanical factors that affect cyclocondensation reactions in a ball mill. Chemical characteristics such as the use or non-use of a catalyst, amount of catalyst and reactants, and product formation, as well as the yield and mechanical factors such as rotation frequency and the number, diameter, and material of the milling balls were evaluated. It was found that a rotation frequency of 450 rpm is efficient for energy transfer to the reactants because the conversion is higher at this rotation. The reaction was highly dependent on the time (3 min) and amount of p-TSA (p-toluenesulfonic acid) utilized as catalyst (10 mol %). Five steel balls of 10 mm were considered to be the ideal number for the efficient mixing of the particles. For this work, the ideal conditions determined were used for the green synthesis of a series of 1Hpyrazoles.

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