scholarly journals Stereoselective Crystallization of Chiral 3,4-Dimethylphenyl Glycerol Ether Complicated by Plurality of Crystalline Modifications

Crystals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 201 ◽  
Author(s):  
Alexander A. Bredikhin ◽  
Dmitry V. Zakharychev ◽  
Zemfira A. Bredikhina ◽  
Alexey V. Kurenkov ◽  
Aida I. Samigullina ◽  
...  
Keyword(s):  
Biological Effects ◽  
Spontaneous Resolution ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Experimental Conditions ◽  
Current Increase ◽  
X Ray ◽  
Crystallization Procedure ◽  
Crystalline Forms ◽  
Racemates Resolution

Spontaneous resolution of Pasteur’s salt was historically the first way to obtain pure enantiomers from the racemate. The current increase in interest in the direct racemates resolution during crystallization is largely due to the opened prospects for the industrial application of this approach. The chiral 3-(3,4-dimethylphenoxy) propane-1,2-diol 1 is a synthetic precursor of practically useful amino alcohols, the enantiomers of which exhibit different biological effects. In this work, it was first discovered that racemic diol 1 is prone to spontaneous resolution. However, the crystallization process is complicated by the existence, along with the conglomerate, of two other crystalline forms. Using the differential scanning calorimetry (DSC) approach, methods have been developed to obtain individual metastable phases, and all identified modifications ((R)-1, (R+S)-1, α-rac-1, β-rac-1) were ranked by energy. The IR spectroscopy and powder X-ray diffraction (PXRD) methods demonstrated the identity of the first two forms and their proximity to the third, while β-rac-1 is significantly different from the rest. The crystal structure of the forms (R)-1 and α-rac-1 was established by the single crystal X-ray diffraction (SC-XRD) method. Preliminary information on the structure of β-rac-1 phase was obtained by the PXRD approach. Based on the information received, the experimental conditions for a successful direct resolution of racemic 1 into individual enantiomers by a preferential crystallization procedure were selected.

scholarly journals Mechanochemical Formation of Racemic Praziquantel Hemihydrate with Improved Biopharmaceutical Properties

Pharmaceutics ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 289
Author(s):  
Debora Zanolla ◽  
Dritan Hasa ◽  
Mihails Arhangelskis ◽  
Gabriela Schneider-Rauber ◽  
Michele R. Chierotti ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Polymorphic Form ◽  
In Vitro Tests ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Experimental Conditions ◽  
Intrinsic Dissolution ◽  
Intrinsic Dissolution Rate ◽  
X Ray ◽  
Enhanced Solubility

Praziquantel (PZQ) is the first-line drug used against schistosomiasis, one of the most common parasitic diseases in the world. A series of crystalline structures including two new polymorphs of the pure drug and a series of cocrystals of PZQ have been discovered and deposited in the Cambridge Structural Database (CSD). This work adds to the list of multicomponent forms of PZQ a relevant example of a racemic hemihydrate (PZQ-HH), obtainable from commercial PZQ (polymorphic Form A) through mechanochemistry. Noteworthy, the formation of the new hemihydrate strongly depends on the initial polymorphic form of PZQ and on the experimental conditions used. The new PZQ-HH has been fully characterized by means of HPLC, Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Hot-Stage Microscopy (SEM), Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), FT-IR, polarimetry, solid-state NMR (SS-NMR), solubility and intrinsic dissolution rate (IDR), and in vitro tests on Schistosoma mansoni adults. The crystal structure was solved from the powder X-ray diffraction pattern and validated by periodic-DFT calculations. The new bioactive hemihydrate was physically stable for three months and showed peculiar biopharmaceutical features including enhanced solubility and a double intrinsic dissolution rate in water in comparison to the commercially available PZQ Form A.

Study of Model Copper-Based Catalysts by Simultaneous Differential Scanning Calorimetry, X-Ray Diffraction and Mass Spectrometry

1987 ◽  
Vol 111 ◽  
Author(s):  
Robert A. Newman ◽  
Joseph A. Blazy ◽  
Timothy G. Fawcett ◽  
Larry F. Whiting ◽  
Robert A. Stowe
Keyword(s):  
Mass Spectrometry ◽  
Differential Scanning Calorimetry ◽  
Copper Oxide ◽  
Cuprous Oxide ◽  
Copper Surface ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Experimental Conditions ◽  
Simultaneous Generation ◽  
X Ray

AbstractRecently, a new materials characterization instrument and technique employing simultaneous differential scanning calorimetry/X-ray diffraction/mass spectrometry (DSC/XRD/MS) have been developed at Dow. Use of this technology can be illlustrated by the study of various materials such as polymers, organics/pharmaceuticals, inorganics, and catalysts.Presented here is the use of the DSC/XRD/MS instrument to study the thermostructural behavior of four model copper-based catalyst systems during activation and regeneration. The instrument allows simultaneous generation of thermal, structural and chemical data in real-time during temperature programmed analysis and provides useful insights into the chemical and physical processes occurring. In addition, the calorimetry data yield qualititative information on the magnitude and rate of heat flow, while the diffraction data provide structural dynamics of reduction, oxidation and crystallite growth.The results of this study conclusively show cuprous oxide as an intermediate in the reduction of the copper oxide portion of each of the model catalysts. However, such features as the onset temperature and copper surface area varied widely among the four catalysts in response to the same chemical event conducted under similar experimental conditions. On the other hand, oxidation runs on the reduced catalysts were all similar to each other, first producing cuprous oxide from copper metal over a broad range of temperature, followed by the oxidation of cuprous oxide to copper oxide at even higher temperatures.

scholarly journals Furosemide solvates: can they serve as precursors to different polymorphs?

2014 ◽  
Vol 70 (a1) ◽  
pp. C1015-C1015
Author(s):  
Vasily Minkov ◽  
Alina Beloborodova ◽  
Valeri Drebushchak ◽  
Elena Boldyreva
Keyword(s):  
Crystal Structures ◽  
X Ray Diffraction ◽  
Melting Points ◽  
Experimental Conditions ◽  
X Ray ◽  
Detailed Structural Analysis ◽  
Rate Of Dissolution ◽  
Crystalline Forms ◽  
Subsequent Decomposition ◽  
Conformational Lability

The importance of polymorphism of molecular crystals is hard to overestimate, especially when dealing with compounds used as materials or drugs. Different polymorphs of a drug substance may have different properties related to their manufacturing, therapeutic usage, or storage (density, hygroscopicity, melting points, thermal stability, solubility, rate of dissolution, surface free energy, toxicity, bioavailability, tabletting, etc.). Different polymorphs, solvates, and co-crystals can be patented, and this opens the way for a competition with brand drugs. Since the energies of different polymorphs are sometimes very close, producing desirable crystalline forms is quite a challenge and can also be complicated by the phenomena of concomitant polymorphism (when several polymorphs crystallize simultaneously from the same batch), or erratic and poorly reproducible (when crystallization gives different polymorphs even at seemingly identical experimental conditions). The aim of the present study was to crystallize various solvates of furosemide, to check whether these solvates can be used as precursors for producing different polymorphs of pure furosemide on their subsequent decomposition upon heating, and to search any correlation between the crystal structures of the solvates and on the furosemide polymorphs produced by desolvation. Four solvates of furosemide with tetrahydrofuran, dioxane, dimethylformamide, and dimethylsulfoxide were crystallized. The detailed structural analysis of furosemide-containing crystal structures showed that the molecule of furosemide has a high conformational lability because of the rotations of the sulfamoyl and furanylmethylamino fragments. Some of the furosemide conformations were shown to be stabilized by the intramolecular N–H···Cl H-bond. Desolvation of the four solvates was studied by TG and X-ray diffraction and was shown to give different products depending on the precursor and particle size.

scholarly journals Structural studies of crystalline forms of triamterene with carboxylic acid, GRAS and API molecules

IUCrJ ◽  
2018 ◽  
Vol 5 (3) ◽  
pp. 309-324 ◽  
Author(s):  
Abida Rehman ◽  
Amit Delori ◽  
David S. Hughes ◽  
William Jones
Keyword(s):  
Analytical Techniques ◽  
Gravimetric Analysis ◽  
Structural Studies ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Evaporative Crystallization ◽  
Structural Database ◽  
Crystalline Forms ◽  
Good Agreement

Pharmaceutical salt solvates (dimethyl sulfoxide, DMSO) of the drug triamterene with the coformers acetic, succinic, adipic, pimelic, azelaic and nicotinic acid and ibuprofen are prepared by liquid-assisted grinding and solvent-evaporative crystallization. The modified ΔpK a rule as proposed by Cruz-Cabeza [(2012). CrystEngComm, 14, 6362–6365] is in close agreement with the results of this study. All adducts were characterized by X-ray diffraction and thermal analytical techniques, including single-crystal X-ray diffraction, powder X-ray diffraction, differential scanning calorimetry and thermal gravimetric analysis. Hydrogen-bonded motifs combined to form a variety of extended tapes and sheets. Analysis of the crystal structures showed that all adducts existed as salt solvates and contained the aminopyridinium–carboxylate heterodimer, except for the solvate containing triamterene, ibuprofen and DMSO, as a result of the presence of a strong and stable hemitriamterenium duplex. A search of the Cambridge Structural Database (CSD 5.36, Version 1.18) to determine the frequency of occurrence of the putative supramolecular synthons found in this study showed good agreement with previous work.

scholarly journals Phase Transitions and Crystal Structures of Ni(II) Complexes Determined with X-ray Powder Diffraction Data

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 106 ◽  
Author(s):  
Hisashi Konaka ◽  
Akito Sasaki
Keyword(s):  
Differential Scanning Calorimetry ◽  
Crystal Structures ◽  
Structural Changes ◽  
Original Form ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Hydrate Form ◽  
X Ray ◽  
Dsc Measurements ◽  
Crystalline Forms

Structural changes of chloride and bromide complexes, [Ni(Et2en)2(H2O)2]Cl2 (designated as 1a) and [Ni(Et2en)2]Br2 (2a), have been investigated by using simultaneous measurements of powder X-ray diffraction (XRD) and differential scanning calorimetry data under the temperature and humidity controls. The hydrate form of chloride complex 1a was transformed into an anhydrate form (1b) by heating at a temperature of 361 K. Then the 1b was reversibly returned to the original 1a by humidification at 25% relative humidity (RH) and temperature of 300 K. On the other hand, the anhydrate form of the bromide complex 2a was first transformed into a hydrate form (2b) at 30% RH and 300 K. On heating, the 2b turned to a new anhydrate form (2c) at 344 K, and then it returned to the original form 2a on further heating. In the present experiments, a series of reactions of 2a proceeded via 2c, which was newly found with the benefit of differential scanning calorimetry (DSC) measurements performed in parallel to the XRD measurements. Crystal structures of new crystalline forms of 1b, 2b, and 2c were determined from the powder XRD data.

scholarly journals Sorption properties of aged cements

2012 ◽  
Vol 76 (8) ◽  
pp. 3411-3423 ◽  
Author(s):  
G. M. N. Baston ◽  
M. M. Cowper ◽  
T. A. Marshall
Keyword(s):  
Calcium Silicate Hydrate ◽  
Deionized Water ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Aged Material ◽  
X Ray ◽  
Untreated Material ◽  
Most Probable Explanation ◽  
Crystalline Forms ◽  
Radionuclide Uptake

AbstractSamples of artificially aged Nirex reference vault backfill (NRVB) were prepared by progressive leaching with deionized water, after which some of the samples underwent hydrothermal treatment. Compared to unaltered NRVB, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) provided evidence for the ageing resulting in alteration of the mineralogy, in particular the absence of portlandite was observed. The specific surface area of NRVB initially increased due to leaching, but then decreased after further leaching.Sorption distribution ratios (RD values) of uranium(VI), neptunium(IV), tin and zirconium onto aged NRVB samples were measured using the batch sorption technique. For all four elements, there was little difference between RD values for aged NRVB and those for untreated material. The most probable explanation for these findings is that even though the ageing treatments altered the NRVB mineralogy, calcium silicate hydrate (C-S-H) phases are responsible for most of the radionuclide uptake and their transformation to more crystalline forms has little effect on the bulk sorption capacity of the aged material.

scholarly journals Structural Characterization of Co-Crystals of Chlordiazepoxide with p-Aminobenzoic Acid and Lorazepam with Nicotinamide by DSC, X-ray Diffraction, FTIR and Raman Spectroscopy

Pharmaceutics ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 648
Author(s):  
Patrycja Garbacz ◽  
Dominik Paukszta ◽  
Artur Sikorski ◽  
Marek Wesolowski
Keyword(s):  
Raman Spectroscopy ◽  
Water Solubility ◽  
Proton Exchange ◽  
Aminobenzoic Acid ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Pharmaceutical Ingredients ◽  
Crystallization Procedure ◽  
Ftir And Raman Spectroscopy

The low water solubility of benzodiazepines seriously affects their bioavailability and, in consequence, their biological activity. Since co-crystallization has been found to be a promising way to modify undesirable properties in active pharmaceutical ingredients, the objective of this study was to prepare co-crystals of two benzodiazepines, chlordiazepoxide and lorazepam. Using different co-crystallization procedures, slurry evaporation and liquid-assisted grinding, co-crystals of chlordiazepoxide with p-aminobenzoic acid and lorazepam with nicotinamide were prepared for the first time. Confirmation that co-crystals were obtained was achieved through a comparison of the data acquired for both co-crystals using differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), Fourier-transform infrared (FTIR) and Raman spectroscopy, with comparisons acquired for the physical mixtures of both benzodiazepines and coformers. The compatibility of PXRD patterns of both benzodiazepines co-crystals with those contained in the base Powder Diffraction File (PDF-4+) suggests that new crystal structures were indeed created under the co-crystallization procedure. Single-crystal X-ray diffraction revealed that a chlordiazepoxide co-crystal with p-aminobenzoic acid and a lorazepam co-crystal with nicotinamide crystallized in the monoclinic P21/n and P21/c space group, respectively, with one molecule of benzodiazepine and one of coformer in the asymmetric unit. FTIR and Raman spectroscopy corroborated that benzodiazepine and coformer are linked by a hydrogen bond without proton exchange. Furthermore, a DSC study revealed that single endothermic DSC peaks assigned to the melting of co-crystals differ slightly depending on the co-crystallization procedures and solvent used, as well as differing from those of starting components.

Studies on the Preparation, Characterization and Solubility of -Cyclodextrin-Roxythromycin Inclusion Complexes

2009 ◽  
Vol 2 (2) ◽  
pp. 523-530
Author(s):  
D. Nagasamy Venkatesh ◽  
S. Karthick ◽  
M. Umesh ◽  
G. Vivek ◽  
R.M. Valliappan ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Inclusion Complexes ◽  
Phase Solubility ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Ir Studies ◽  
Poorly Soluble ◽  
Poorly Soluble Drug

Roxythromycin/ β-cyclodextrin (Roxy/ β-CD) dispersions were prepared with a view to study the influence of β-CD on the solubility and dissolution rate of this poorly soluble drug. Phase-solubility profile indicated that the solubility of roxythromycin was significantly increased in the presence of β-cyclodextrin and was classified as AL-type, indicating the 1:1 stoichiometric inclusion complexes. Physical characterization of the prepared systems was carried out by differential scanning calorimetry (DSC), X-ray diffraction studies (XRD) and IR studies. Solid state characterization of the drug β-CD binary system using XRD, FTIR and DSC revealed distinct loss of drug crystallinity in the formulation, ostensibly accounting for enhancement of dissolution rate.

scholarly journals Zeolite NaP1 Functionalization for the Sorption of Metal Complexes with Biodegradable N-(1,2-dicarboxyethyl)-D,L-aspartic Acid

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2518
Author(s):  
Dorota Kołodyńska ◽  
Yongming Ju ◽  
Małgorzata Franus ◽  
Wojciech Franus
Keyword(s):  
Experimental Data ◽  
Aspartic Acid ◽  
Ph Value ◽  
Complexing Agents ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
Modified Zeolite ◽  
X Ray ◽  
Slow Release Fertilizers ◽  
Pseudo Second Order

The possibility of application of chitosan-modified zeolite as sorbent for Cu(II), Zn(II), Mn(II), and Fe(III) ions and their mixtures in the presence of N-(1,2-dicarboxyethyl)-D,L-aspartic acid, IDHA) under different experimental conditions were investigated. Chitosan-modified zeolite belongs to the group of biodegradable complexing agents used in fertilizer production. NaP1CS as a carrier forms a barrier to the spontaneous release of the fertilizer into soil. The obtained materials were characterized by Fourier transform infrared spectroscopy (FTIR); surface area determination (ASAP); scanning electron microscopy (SEM-EDS); X-ray fluorescence (XRF); X-ray diffraction (XRD); and carbon, hydrogen, and nitrogen (CHN), as well as thermogravimetric (TGA) methods. The concentrations of Cu(II), Zn(II), Mn(II), and Fe(III) complexes with IDHA varied from 5–20 mg/dm3 for Cu(II), 10–40 mg/dm3 for Fe(III), 20–80 mg/dm3 for Mn(II), and 10–40 mg/dm3 for Zn(II), respectively; pH value (3–6), time (1–120 min), and temperature (293–333 K) on the sorption efficiency were tested. The Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin adsorption models were applied to describe experimental data. The pH 5 proved to be appropriate for adsorption. The pseudo-second order and Langmuir models were consistent with the experimental data. The thermodynamic parameters indicate that adsorption is spontaneous and endothermic. The highest desorption percentage was achieved using the HCl solution, therefore, proving that method can be used to design slow-release fertilizers.

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