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Bauer‐Brandl, Annette; Marti, E.; Geoffroy, A.; Poso, Antti; Suurkuusk, J.; Wappler, Eberhard; Bauer, Klaus

doi:10.1023/a:1010137505058

Cited by 22 publications

(10 citation statements)

References 9 publications

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“…The energy difference between forms I and II is 9.07 kJ mol À1 , slightly higher than 6 kJ mol À1 , which is in agreement with the observation that conformational polymorphs have higher lattice energy differences. 50 Two forms have similar calculated densities at 296 K (I: 1.284 g cm À3 and II: 1.276 g cm À3 ). While form I is slightly denser than form II, its lattice energy is higher than that of form II, which might be due to the hydrogen bond difference between the two forms, since form II has a shorter and more linear hydrogen bond than form I.…”

Section: Computational Resultsmentioning

confidence: 88%

Solution growth and thermal treatment of crystals lead to two new forms of 2-((2,6-dimethylphenyl)amino)benzoic acid

Zhoujin

et al. 2018

RSC Adv.

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We report the discovery of two new forms (II and III) of a potential non-steroidal anti-inflammatory and thyroid drug, 2-((2,6-dimethylphenyl)amino)benzoic acid (HDMPA) through solution growth and thermal treatment of crystals. Form II has been discovered through crystal growth in a variety of solvents, and characterized by single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), FT-IR, and Raman spectroscopy. Form II converts into form III upon thermal treatment, as indicated by the phase behavior study of form II with differential scanning calorimetry (DSC). Form III has been characterized by IR, Raman and PXRD. Conformational flexibility of the molecule seems to lead to the polymorphism of the system. A conformational scan shows the conformational minima correspond to the conformers in the polymorphs. Lattice energy calculations show energies of À48.14 and À50.31 kcal mol À1 for forms I and II, providing information on the relative stability for each form. Hirshfeld analysis revealed that

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Section: Computational Resultsmentioning

confidence: 88%

Solution growth and thermal treatment of crystals lead to two new forms of 2-((2,6-dimethylphenyl)amino)benzoic acid

Zhoujin

et al. 2018

RSC Adv.

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“…We have used this approach previously to measure differences between other drug modifications. 20,21 In the present study, ethanol was chosen as the solvent, because felodipine dissolves well with a large endothermic heat effect. The results of the calorimetric experiments are summarized in Scheme 1 (see Table S2 of the Supporting Information for a full data set).…”

Section: Table 3 Intermolecular Hydrogen Bonds In Polymorphs I− IVmentioning

confidence: 63%

Crystallization and Polymorphism of Felodipine

Surov

Solanko

Bond

et al. 2012

Crystal Growth & Design

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Two previously known polymorphs (forms I and II) and two new polymorphs (forms III and IV) of the calcium-channel blocker felodipine were obtained during attempts to cocrystallize the compound with a variety of potential cocrystal formers. A correlation was observed between the polymorphic outcome and the effective pH value in the presence of the cocrystal former, and it was possible subsequently to produce the four polymorphs by pH adjustment using H2SO4(aq) or NaOH(aq). This suggests that there is no distinct “structure-directing” role for the molecular additives present during the cocrystallization trials. The crystal structures of the new forms III and IV were determined using single-crystal X-ray diffraction. Forms I, II, and III were obtained in bulk form and characterized by a variety of analytical methods, including thermal analysis, solution calorimetry, intrinsic dissolution rate measurement, and solubility measurement. Form IV could be obtained only as a few isolated single crystals, and its crystallization could not be reproduced. On the basis of the measured thermochemical data and solubility studies, form I appears to be the thermodynamically most stable phase at ambient conditions, although the new form III is practically isoenergetic. Form II shows the highest solubility and intrinsic dissolution rate, consistent with the lowest thermodynamic stability. Forms I, II, and III are all monotropically related.

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“…One can suggest that the difference in the energies of the tolazamide polymorphs is so small that a phase transition between them may be classified as an “isoenergetic phase transition” 62. 63 This hypothesis is additionally supported by the fact that melting of all three polymorphs was observed in the DSC experiments at practically the same temperature and with practically the same melting enthalpies (Figure 4). One can also consider the possible role of solvent inclusions in the samples of Form II in triggering the phase transition, similar to what has been previously observed for paracetamol polymorphs.…”

Section: Resultsmentioning

confidence: 88%

Isoenergetic Polymorphism: The Puzzle of Tolazamide as a Case Study

Boldyreva

Arkhipov

Drebushchak

et al. 2015

Chemistry A European J

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In the present case study of tolazamide we illustrate how many seemingly contradictoryr esults that have been obtained from experimental observationsa nd theoretical calculationsc an finally startf ormingaconsistent picture: a" puzzle put together". For many years, tolazamide was considered to have no polymorphs. This made this drug substance unique amongt he large familyo fs ulfonylureas, which was known to be significantly more pronet op olymorphism than many other organic compounds. The present work employs ab road and in-deptha nalysist hat includest he use of optical microscopy,s ingle-crystal and powder X-ray diffraction,I Ra nd Ramans pectroscopies, DSC, semiempiricalP IXEL calculations and DFT of three polymorphs of tolazamide. This case study showsh ow the polymorphs of amolecular crystalc an be overlooked even if discovered serendipitously on one of numerous crystallizations, and how very different molecular packings can be practically isoenergetic but still crystallize quite selectively and transform one into anotherirreversibly upon heating.

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Cited by 22 publications

References 9 publications

Solution growth and thermal treatment of crystals lead to two new forms of 2-((2,6-dimethylphenyl)amino)benzoic acid

Solution growth and thermal treatment of crystals lead to two new forms of 2-((2,6-dimethylphenyl)amino)benzoic acid

Crystallization and Polymorphism of Felodipine

Isoenergetic Polymorphism: The Puzzle of Tolazamide as a Case Study

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