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Relevant bibliographies by topics / Polymorphism (crystallography)

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Academic literature on the topic 'Polymorphism (crystallography)'

Author: Grafiati

Published: 4 June 2021

Last updated: 6 September 2023

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Journal articles on the topic "Polymorphism (crystallography)"

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Baias, Maria, Renny Mathew, Ivan Sergeyev, Karolina Uchman, Melanie Rosay, Fabien Aussenac, Werner Maas, Chris J. Pickard, and Bart Kahr. "NMR crystallography advancements for exploring polymorphism." Acta Crystallographica Section A Foundations and Advances 75, a1 (July 20, 2019): a278. http://dx.doi.org/10.1107/s0108767319097277.

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Tirkkonen, B., A. Aukrust, E. Couture, D. Grace, Y. Haile, K. M. Holm, H. Hope, Å. Larsen, H. Sivertsen Lunde, and C. E. Sjøgren. "Physicochemical characterisation of mangafodipir trisodium." Acta Radiologica 38, no. 5 (September 1997): 780–89. http://dx.doi.org/10.1080/02841859709172411.

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Purpose: To determine the structure and various physicochemical properties of man-gafodipir (MnDPDP) trisodium, the active ingredient of Teslascan, a new organ-specific contrast medium for MR imaging. Material and Methods: The structure of MnDPDP trisodium crystals was determined by X-ray crystallography. The possible existence of polymorphism in MnDPDP trisodium was evaluated by powder X-ray diffraction, optical microscopy, thermal analysis and IR spectroscopy. In addition, various spectroscopic techniques and physicochemical measurements were used for characterisation of MnDPDP trisodium. Results: The crystallographic data obtained for MnDPDP trisodium show that the general core structure of the MnDPDP anion is similar to that seen in related substances. The metal coordination geometry is a distorted octahedron defined by 2 phenolate oxygens, 2 carboxylate oxygens and 2 amine nitrogens. The unit cell contains 2 MnDPDP anions, 6 sodium ions and 50 water molecules. The various spectroscopic data are consistent with the structure determined by X-ray crystallography. The product (Teslascan) has low viscosity, is isotonic with blood and has a physiological pH. Conclusion: MnDPDP trisodium is a crystalline, hygroscopic solid which is readily soluble in water. No evidence of polymorphism was seen in the samples studied.

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Katrusiak, Andrzej. "High-pressure crystallography." Acta Crystallographica Section A Foundations of Crystallography 64, no. 1 (December 21, 2007): 135–48. http://dx.doi.org/10.1107/s0108767307061181.

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Since the late 1950's, high-pressure structural studies have become increasingly frequent, following the inception of opposed-anvil cells, development of efficient diffractometric equipment (brighter radiation sources both in laboratories and in synchrotron facilities, highly efficient area detectors) and procedures (for crystal mounting, centring, pressure calibration, collecting and correcting data). Consequently, during the last decades, high-pressure crystallography has evolved into a powerful technique which can be routinely applied in laboratories and dedicated synchrotron and neutron facilities. The variation of pressure adds a new thermodynamic dimension to crystal-structure analyses, and extends the understanding of the solid state and materials in general. New areas of thermodynamic exploration of phase diagrams, polymorphism, transformations between different phases and cohesion forces, structure–property relations, and a deeper understanding of matter at the atomic scale in general are accessible with the high-pressure techniques in hand. A brief history, guidelines and requirements for performing high-pressure structural studies are outlined.

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G, Nithya, Sudha R, and Charles C. Kanakam. "Polymorphic behavior of an organic compound." Asian Journal of Pharmaceutical and Clinical Research 10, no. 4 (April 1, 2017): 259. http://dx.doi.org/10.22159/ajpcr.2017.v10i4.16702.

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Objective: Polymorphic crystals were exhibited in many organic compounds. The frequency changes, relative intensities, band contours, and numberof bands were observed in the spectra of different polymorphism which may be due to molecule-molecule interactions in the crystal unit cells. Theshape of a molecule at its site in the unit cell is distorted by molecular interactions.Methods: The identification of a pure crystal form and to quantify a mixture of two forms infrared and Raman spectra of different crystalline formsof the same organic compound can be used. 2’-chloro-4-methoxy-3-nitro benzil (1) was synthesized and its two polymorphic forms were obtainedby recrystallization from the solvents acetone/chloroform and ethanol. The polymorphism present in the compound was confirmed by single crystalX-ray crystallography and differential scanning calorimetry.Results: The polymorph 1.1 crystallizes as triclinic P-1 space group in the solvent acetone – chloroform and the polymorph 1.2 crystallizes asmonoclinic P21/c space group in the solvent ethanol.Discussion: The intermolecular lattice energy and the interplay of molecular conformation in the crystallization and stability of polymorphs areidentified by X-ray crystal structures of conformational polymorphs.Keywords: Conformational polymorphism, Organic compounds, Single crystal growth, X-ray diffraction.

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Cogoni, M., B. D'Aguanno, L. N. Kuleshova, and D. W. M. Hofmann. "A powerful computational crystallography method to study ice polymorphism." Journal of Chemical Physics 134, no. 20 (May 28, 2011): 204506. http://dx.doi.org/10.1063/1.3593200.

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Gholivand, Khodayar, Farzaneh Afshar, Zahra Shariatinia, and Karim Zare. "Polymorphism for a novel phosphoramidate; NMR and X-ray crystallography." Structural Chemistry 21, no. 3 (February 11, 2010): 629–36. http://dx.doi.org/10.1007/s11224-010-9592-z.

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Wang, Jungang, Yang Gao, Jiachen Xiang, Miao Wang, and Anxin Wu. "X-ray studies of conformation: observation of conformational polymorphism of a glycoluril clip." CrystEngComm 17, no. 11 (2015): 2245–49. http://dx.doi.org/10.1039/c5ce00066a.

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Kálmán, Alajos. "Morphotropism: link between the isostructurality, polymorphism and (stereo)isomerism of organic crystals." Acta Crystallographica Section B Structural Science 61, no. 5 (September 23, 2005): 536–47. http://dx.doi.org/10.1107/s0108768105023189.

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An ongoing analysis of the supramolecular self-assembly of disubstituted cycloalkanes has led to the discovery of seven packing patterns built up from hydrogen-bonded homo- and heterochiral chains of racemic molecules, associated in either antiparallel or parallel arrays [Kálmán et al. (2001). Acta Cryst. B57, 539–550]. Two further patterns have been revealed in the close packing of analogous alicyclic β-amino acids [Fábián et al. (2005). Cryst. Growth Des. 5, 773–782]. Since each pattern is represented by at least one crystal structure, the chemical similarity and crystallographic forms of these crystals have facilitated the recognition that these patterns differ by one or two rotation(s) of the common motifs (e.g. dimers, tetramers, helices etc.), or the whole pattern may rotate through 180° in an oblique unit cell. Such non-crystallographic – with the exception of polymorphism – virtual rotations as a whole may be denoted by the expression morphotropism. According to Kitaigorodskii [(1961), Organic Chemical Crystallography, pp. 222–231. New York: Consultants Bureau], morphotropism is an attempt to keep the packing coefficient above 0.6 whenever there are alternative possibilities for the structures of closely related molecules. It has been found that crystals of stereoisomers are also frequently related by such virtual rotations. Similarly, non-crystallographic rotations effect bridges between homostructural crystals [Kálmán et al. (1993b). Acta Cryst. B49, 1039–1049] and occasionally hallmark the polymorphism of organic compounds [Kálmán et al. (2003) J. Am. Chem. Soc. 125, 34–35]. In polymorphs, however, such rotations really transform one molecule into another in order to achieve a better packing mediated by solvents, temperature etc.

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Dubrovinsky, Leonid. "Polymorphism and electronic transformations of deep Earth minerals." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C37. http://dx.doi.org/10.1107/s2053273314099628.

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While powder X-ray diffraction studies stepped over a megabar in pressure already in the 1970s, single crystal experiments remained much rarer and covered until recently a very limited pressure range barely reaching 15 GPa. Recent technological advances resulted in a revolutionary breakthrough in the high-pressure crystallography. The structure solution and the full refinement are now possible at pressures over 100 GPa. A comprehensive understanding of the iron- and aluminum-bearing magnesium silicate perovskite (Pv) and post-perovskite (PPv, CaIrO3-type) crystal structures and their evolution under pressure and temperature is vital for evaluating seismic data of the Earth's lower mantle. We investigated materials with different compositions and iron oxidation states by means of single-crystal X-ray diffraction at pressures over 150 GPa and temperatures over 2500 K, and by Mössbauer spectroscopy. By structural studies of Pv at extreme conditions, we found (a) no spin state crossover in ferric iron occupying the bicapped trigonal prism ("A" crystallographic site), and (b) no crystal-chemically significant amount of ferric iron in the octahedral "B-site at any conditions of our experiments. We synthesized single crystals of PPv, refined their structure and distribution of iron between the structural sites. We demonstrated that incorporation of ferric iron and aluminum significantly increases the compressibility of magnesium silicate Pv and PPv. Based on experimental data we constrained the thermal equation of state for Pv and PPv with a variable content of iron (ferrous and ferric) and aluminum. We concluded that variation of Fe3+/ΣFe can lead to significant changes of Pv bulk sound velocity (over 1%) demonstrating that the oxidation state of iron is a critical parameter for interpretation of seismic tomography data.

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Kálmán, Alajos, and László Fábián. "Structural similarities in tetraaryltins described by virtual non-crystallographic rotations or translations: Kitaigorodskii's morphotropism is revisited." Acta Crystallographica Section B Structural Science 63, no. 3 (May 16, 2007): 411–17. http://dx.doi.org/10.1107/s0108768107010968.

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Recently Kálmán [(2005), Acta Cryst. B61, 536–547] revealed that semirigid molecules or their patterns held together e.g. by hydrogen bonds may perform non-crystallographic rotations (through 180, 90° etc.) around themselves whenever a substitution, ring enlargement or isomerization destroys the existing close packing, i.e. the novel substituent or the enlarged ring can no longer fit in the hollows formed between the molecules. In other words, the old and new arrangements of such chemically similar molecules can be converted into each other by virtual rotations. However, when a semirigid molecule without substitution, but under the influence of solvents, temperature etc., is fully or partly rearranged in the solid state, the corresponding non-crystallographic rotation (hereinafter ncr) is real and gives rise to polymorphism. Such polymorphs are hallmarked by full or partial isostructurality and show that ncrs always occur together with isostructurality. First Kitaigorodskii [(1961), Organic Chemical Crystallography, New York: Consultants Bureau] reported on the structural similarity of three tetraaryltins, (p-RC6H4)4Sn, R = H, CH3, CH3O, which is terminated by the larger C2H5O group. A revisit to these structures revealed that the tetragonal → monoclinic conversion termed by Kitaigorodskii as a `morphotropic step' is also performed by an ncr. Similarly, other tetraaryltins in the literature are related by ncrs or the nc translation of the semirigid tetrahedra, or they remain isostructural. Since one of the definitions of morphotropism, a word of Greek origin, is `turn of form', the ncrs of semirigid molecules can be denoted – following Kitaigorodskii – by this word, whereas its alternative definition in the morphological crystallography of `unidirectional changes' [applied by Groth (1870). Ber. Chem. Ges. 3, 449–457] covers the non-crystallographic translations described first in this work.

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Dissertations / Theses on the topic "Polymorphism (crystallography)"

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Hammond, Robert Paul. "The structural chemistry of the stuffed tridymites A[BPO4] (A=Na; Ag; b=Be, Co, Zn) and A[BCO4] (A=Na, K; B=Al, Fe; C=Si, Ge) /." *McMaster only, 1996.

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Donahue, Michael J. "Polymorph characterization and control /." View online ; access limited to URI, 2007. http://0-digitalcommons.uri.edu.helin.uri.edu/dissertations/AAI3276988.

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Wells, David F. "Experimental and computational study of the detection and stability of polymorphs using PXRD, DSC and solubility /." View online ; access limited to URI, 2008. http://0-digitalcommons.uri.edu.helin.uri.edu/dissertations/AAI3314449.

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Chavez, Krystle J. "Crystallization of pseudopolymorphic forms of sodium naproxen in mixed solvent systems." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29759.

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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Rousseau, Ronald; Committee Member: Meredith, Carson; Committee Member: Prausnitz, Mark; Committee Member: Teja, Amyn; Committee Member: Wilkinson, Angus. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Strachan, Clare, and n/a. "Spectroscopic investigation and quantitation of polymorphism and crystallinity of pharmaceutical compounds." University of Otago. School of Pharmacy, 2005. http://adt.otago.ac.nz./public/adt-NZDU20070427.141108.

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Spectroscopy is increasingly used to investigate and monitor the solid state forms of pharmaceutical materials and products. Spectroscopy�s speed, nondestructive sampling, compatibility with fibre optics and safety also make it attractive for in-line monitoring. In this thesis, the spectroscopic techniques Fourier transform Raman spectroscopy, terahertz pulsed spectroscopy and second harmonic generation were used to characterise and quantify polymorphism and crystallinity of pharmaceutical compounds. Where possible, the multivariate analysis technique partial least squares was used for quantitative analysis. Fourier transform Raman spectroscopy detects polarisability changes mainly associated with molecular vibrations. Terahertz pulsed spectroscopy is a new spectroscopic technique that operates between the infrared and microwave regions of the electromagnetic spectrum and detects dipole moment changes mainly associated with crystalline phonon vibrations in the solid state. Second harmonic generation is a nonlinear optical phenomenon that depends on the dipole moment in crystals and crystal symmetry. Several materials capable of existing in different solid state forms were used. FT-Raman spectroscopy was able to differentiate carbamazepine forms I and III, enalapril maleate forms I and II and γ-crystalline and amorphous indomethacin. Combined with partial least squares the technique could quantify binary mixtures of CBZ forms I and III with a limit of detection as low as 1%, and mixtures of enalapril maleate with a limit of detection of as low as 2%. Terahertz pulsed spectroscopy obtained very different spectra for carbamazepine forms I and III, enalapril maleate forms I and II, γ-crystalline and amorphous indomethacin, crystalline and supercooled thermotropic liquid crystalline fenoprofen calcium, three forms of lactose, and five forms of sulphathiazole. At present the modes in the spectra cannot be attributed to specific phonon modes. Quantitation of binary mixtures of different forms of a compound using partial least squares analysis usually resulted in a limit of detection of about 1%. Second harmonic generation was used to quantify binary mixtures of different forms of enalapril maleate and lactose, as well as binary mixtures of enalapril maleate form II and polyvinylpyrrolidone. A quantitative relationship was present for each of the mixtures, however the limits of detection were usually above 10%. The high value is probably due to the machine being a prototype and univariate analysis associated with a single output variable. Future improvements to the apparatus and measurement parameters are likely to reduce the limits of detection. Ranitidine hydrochloride polymorphs could also be differentiated using second harmonic generation, however γ-crystalline and amorphous indomethacin and forms I and III of carbamazepine could not. The methods used in this thesis were successfully used for qualitative and quantitative analysis of polymorphism and crystallinity of pharmaceutical compounds. TPS and SHG are useful additions to the range of experimental techniques that can be used to investigate and monitor properties of pharmaceutical solids.

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Tian, Fang, and n/a. "Towards a deeper understanding of the polymorphic conversion of carbamazepine in aqueous suspension." University of Otago. School of Pharmacy, 2007. http://adt.otago.ac.nz./public/adt-NZDU20070601.135438.

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Polymorphism can influence every aspect of the properties of a solid including the shelf life, dissolution rate, solubility, formulation properties and processing properties of a solid drug. A deeper understanding of polymorphism and related solid state properties would ensure an improved quality of the materials used throughout drug preparation, dosage form formulation and clinical trials. Therefore, determination of the existence of polymorphs and pseudopolymorphs, characterization of different solid state forms and their respective properties, and controlling the existing form in the resulting formulation all form part of a rapidly growing field within pharmaceutical research and industry. Carbamazepine (CBZ) was the model drug used in this study. FT-Raman spectroscopy was chosen as a main investigative technique in this study to evaluate its potential in monitoring (pseudo)polymorphic conversions in aqueous suspensions in the absence or presence of various pharmaceutical excipients. Partial least squares analysis (PLS) was used for quantitative analysis of the spectral data. Earlier it has been found that CBZ converts rapidly to the dihydrate (DH) when exposed to humidity or water, and this has been reported to be the main reason for the sometimes observed greatly decreased bioavailability of marketed CBZ tablets. In this study, the conversion kinetics of CBZ (forms I, II and III) to DH in aqueous suspension were found to be first order kinetics with an unconverted portion (R� [greater than or equal to] 0.95), where the crystal morphology appeared to play a more important role in its conversion kinetics than the polymorphic form. The influence of pharmaceutical excipients on the conversion of CBZ in aqueous suspension was also explored. For excipients such as methylcellulose (MC), hydroxypropyl methylcellulose (HPMC) and hydroxypropyl cellulose (HPC) which have both a low solubility parameter (< 27.0 MPa[1/2]) and strong hydrogen bonding groups, complete inhibition of the conversion of CBZ was possible even at a very low concentration (0.1 % w/v). Raman spectroscopy showed its high applicability in investigating CBZ conversion kinetics and screening of excipient effects in aqueous environment. It was demonstrated that Raman has a robust nature in quantitative analysis since problems such as different particle size, morphology, and spatial distribution of the two solid state forms of the drug seemed not to have significant influence on Raman scattering. This study has also clarified the relative importance of many contributing factors (type of crystalline form (CBZ or DH), crystal morphology, surface area, and excipient interactions with drug particles) influencing the in vitro dissolution of CBZ. The solid state characterization approach taken in this study will provide a deeper insight into the dissolution performance of drugs and should thus lead to a better understanding of in vitro/in vivo behavior of drugs.

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Johnstone, Russell D. L. "Effect of high pressure on structural oddities." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/3784.

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This thesis describes the effect of pressure on crystal structures that are in some way unusual. The aim was to investigate whether pressure could be used to force these ‘structural oddities’ to conform to more conventional behaviour. In many cases pressure-induced phase transitions were observed, and the driving forces of these are considered. L-serine monohydrate crystallises with layers of hydrogen bonded serine molecules. Layers are linked together by H-bonds from the donor atoms of water molecules. The orientation of the water molecules between the layers is uncommon for other layered hydrates in the CSD. A single crystal of serine hydrate undergoes a pressure-induced phase transition at 5 GPa, which is characterised by a rotation of the water molecules to an orientation which is more frequently observed. PIXEL calculations show that the transition is driven by the PV term in the equation G = U - TS + PV. An attempt to reproduce the transition in another layered hydrate with a similar topology was partially successful in the compression of S-4-sulfo-L-phenylalanine monohydrate, which undergoes a similar phase transition at 1 GPa. Methyl 2-(9H-carbazol-9-yl)benzoate crystallises unusually with eight molecules in the asymmetric unit (Z’ = 8). Compression of a single crystal results in a phase transition at ca. 5 GPa to give a Z’ = 2 polymorph. The PV term is an important contributor to the driving force of the transition. The geometries of the molecules in phase-II are significantly less stable than in phase-I, and as pressure is released on phase-II the need to adopt a more stable molecular conformation eventually outweighs the PV advantage. The Z’ = 8 structure is eventually re-established at 4.6 GPa. This work illustrates how low Z’ polymorphs of the same structure are not always the thermodynamically more stable forms. When recrystallised in situ from a 4:1 by volume solution of methanol and ethanol, a new polymorph of salicylamide is obtained at 0.2 GPa. The ambient pressure phase appears in the CSD to contain a number of abnormally short H…H contacts. We find this model to be incorrect, and have re-determined the structure to find no short H…H contacts. PIXEL and DFT calculations indicate that the high-pressure polymorph is favoured over the ambient phase by the PV term, the zero point energy and entropy. Low completeness that often occurs as a result of shading from the high-pressure cell was improved by the inclusion of multiple crystals within the sample chamber. Bianthrone changes colour from yellow to green on grinding, though this does not occur when subjected to hydrostatic pressure to 6.5 GPa. There is, however, a subtle colour change from bright yellow to dark orange as pressure is applied, and it is likely that this is caused by changes in the - stacking distances. This work highlights how a system can react differently to hydrostatic and non-hydrostatic conditions.

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Cooper, Brian J. "The investigation of the optical properties of polytypic minerals." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/53682.

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A new approach to the investigation of the optical properties of polytypic minerals that combines spindle stage techniques, X-ray diffraction methods, electron microprobe analysis, and dielectric tensor calculations has been developed and applied to zinc sulfides and chloritoids. For the first time, X—ray diffraction studies of natural anisotropic zinc sulfides have documented the simultaneous occurrence of twinning and stacking disorder along more than one of the four symmetry equivalent <111> directions of sphalerite. Precession photographs of optically anisotropic zinc sulfides are characterized by twin—equivalent diffraction maxima and diffuse diffraction streaking along lattice rows with (h-k) ≠ 3n (equivalent hexagonal indices) in one or two <111> directions. A system of linear equations has been used to calculate the approximate volume fractions of each twin domain and the sphalerite host domain. Dielectric tensor calculations have been performed to illustrate that mixtures of cubic and hexagonal zinc sulfide may be optically biaxial if the intergrowth occurs along more than one of the symmetry equivalent <111> directions of sphalerite (cubic). The dependence of the optical properties upon the chemical variation and polytypic intergrowth in the Hg-Fe chloritoids has been investigated. The effects of the variation in chemical composition of specific polytypic compositions were analyzed first. The refractive indices of 10 approximately pure 2M₂ Hg-Fe chloritoids show strong correlations (R² ≥ 0.094) to the proportion of Hg cations in the H(1B) site, Hg/(Hg + Fe + Hn) - HGN. Correlations between the optical orientation angles and HGN were weaker (R² ≤ 0.87). The optical orientation is very sensitive to small variations in the polytypic composition, especially orientation angles that have fixed values in 2M₂ chloritoid. The parameter showing the most sensitivity is ∠ X ⋀ b, which is 0° in an ideal 2M₂ chloritoid, but increases to about 6° for a chloritoid containing 10% by volume 1Tc polytype. The sum of ∠ Y ⋀ c* and ∠ Z ⋀ c* for an ideal 2M₂ chloritoid has a value of 90°, whereas a chloritoid with 10% 1Tc has a sum of 92°. Although not as sensitive as ∠ X ⋀ b, this parameter can be determined with only a spindle stage or universal stage. The observed dependence of the optical properties on polytypic intergrowth and chemical variation has been modeled using dielectric tensor calculations based on the properties of a 1Tc layer and assuming that the 2M₂ polytype is derived by twinning the 1Tc polytype about [010] with an (001) composition plane.
Ph. D.

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Zelaya, Carlos A. "6,6’-Dimethoxygossypol: Molecular Structure, Crystal Polymorphism, and Solvate Formation." ScholarWorks@UNO, 2011. http://scholarworks.uno.edu/td/136.

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6,6’-Dimethoxygossypol (DMG) is a natural product of the cotton variety Gossypium barbadense and a derivative of gossypol. Gossypol has been shown to form an abundant number of clathrates with a large variety of compounds. One of the primary reasons why gossypol can form clathrates has been because of its ability to from extensive hydrogen bonding networks due to its hydroxyl and aldehyde functional groups. Prior to this work, the only known solvate that DMG formed was with acetic acid. DMG has methoxy groups substituted at two hydroxyl positions, and consequently there is a decrease in its ability to form hydrogen bonds. Crystallization experiments were set up to see whether, like gossypol, DMG could form clathrates. The following results presented prove that DMG is capable of forming clathrates (S1 and S2) and two new polymorphs (P1 and P2) of DMG have been reported.

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Bayés-García, Laura. "Polymorphism and Solid State Miscibility of Triacylglycerols. Application to Food Authentication." Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/129313.

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Esta tesis se basa fundamentalmente en el estudio in situ del polimorfismo de triacilgliceroles (TAGs) mayoritarios de aceites y grasas alimentarios, la determinación del comportamiento de fases de algunas de sus mezclas binarias, y la aplicación del polimorfismo como herramienta para la autentificación de productos alimentarios. Se ha llevado a cabo la caracterización polimórfica de los TAGs POP, OPO, POO, POL, SOO, OOO y OOL, básicamente utilizando una combinación de calorimetría diferencial de barrido y difracción de rayos X con radiación sincrotrón (SAXD y WAXD). Así, se han podido monitorizar los procesos dinámicos de cristalización y las transiciones polimórficas cuando las muestras se sometían a diferentes velocidades de enfriamiento y calentamiento. Los resultados obtenidos son directamente aplicables a procesos de cristalización de aceites y grasas alimentarios, con la finalidad de obtener las propiedades deseadas del producto final, utilizando los tratamientos térmicos más eficientes. Para comprender las interacciones intermoleculares que tienen lugar entre TAGs, se ha determinado los diagramas de fases de las mezclas PPO-OPO, PPO-POO y POO-OPO. Se ha observado un comportamiento eutéctico para el sistema PPO-OPO, mientras que en los sistemas PPO-POO y POO-OPO se formaba un compuesto molecular (co-cristal) metaestable, que tendía a separarse en los componentes de origen. Mediante el uso de difracción de rayos X con micro-haz de radiación sincrotrón, se han analizado las microestructuras heterogenias de mezclas de POP-OPO. El estudio de estos agregados cristalinos esferulíticos es directamente aplicable a procesos de fraccionamiento del aceite de palma. Con la finalidad de comprender muestras grasas más complejas, se ha caracterizado el complejo comportamiento polimórfico de mezclas multi-componente de 3 a 6 TAGs. Para el caso particular del aceite de oliva, el comportamiento polimórfico viene básicamente determinado por los TAGs mayoritarios, mientras que los componentes minoritarios parecen desarrollar un papel menos crucial. Finalmente, se ha aplicado el comportamiento polimórfico como herramienta para la autentificación y detección de fraudes en productos alimentarios. Ha sido posible determinar adiciones fraudulentas de aceite de avellana en aceite de oliva virgen extra en concentraciones inferiores al 5%, y se han podido establecer diferencias muy significativas en grasas de jamones Ibéricos de las categorías cebo y bellota.
Lipids, together with proteins and carbohydrates are major nutrients and also employed as lipophilic materials in food, cosmetic and pharmaceutical industries. Alimentary and industrial fats and oils (such as vegetable oils, margarine, chocolate, and confectionery fats) mainly consist of triacylglycerols (TAGs), whose molecules involve different types of fatty acid moieties. TAGs show a complicated crystallization behavior. The physicochemical properties of a TAG molecule are determined by the nature and compositions of the three fatty acid moieties. These properties must be studied not only in their pure systems but also in mixed systems. In particular, studies on binary mixture systems provide valuable information about molecular interactions among different lipid materials. This PhD thesis is based on the study of the in situ polymorphic characterization of the main TAGs of some vegetable and animal fats and oils, some of their mixtures and the use of the polymorphic behavior of edible fats and oils as a tool to determine their authentication. The polymorphic study of the triacylglycerols POP, OPO, POO, POL, SOO, OOO and OOL was in situ characterized by mainly using differential scanning calorimetry (DSC) and synchrotron radiation X-ray diffraction (SR-XRD) with SAXD and WAXD simultaneous measurement. The combined usage of DSC and SR-XRD or laboratory-scale X-ray diffraction enabled us to monitor the occurrence and transformation behavior at different rates of cooling and heating. The results obtained are closely related to actual crystallization processes of edible fats and oils, in which most functional polymorphic forms can be obtained by applying the most efficient thermal treatments. We also determined the phase behavior of binary mixtures of mixed-acid TAGs containing palmitic and oleic fatty acids (i.e. PPO-OPO, PPO-POO and POO-OPO). PPO-OPO system revealed an eutectic behavior, whereas PPO-POO and POO-OPO were molecular compound-forming. Long incubation periods were needed in order to thermodynamically stabilize the binary mixtures, and the results demonstrated that molecular compounds of PPO-POO and POO-OPO were metastable and tended to separate into the pure TAG components. On the other hand, microstructures of spherulites of POP-OPO binary mixtures were analyzed in neat liquid and solution (n-dodecane) systems by using synchrotron radiation microbeam X-ray diffraction (SR-mu-XRD). Due to a molecular compound formation at the 50:50 concentration ratio, 75POP:25OPO and 25POP:75OPO compositions were characterized to study how the microstructures of spherulites of the TAGs mixtures are determined when the molecular compound crystals and POP or OPO component crystals can be formed competitively. Studies of these heterogeneous microstructures in neat liquid and solution are applicable to palm oil fractionation processes by dry and solvent methods. In an attempt to make an approach to complex natural fatty samples, such as olive oil, the polymorphism of multicomponent mixtures (from 3 to 6 TAG components) was analyzed and discussed. Thus, we observed that the polymorphic behavior of an extra virgin olive oil from the Arbequina olive variety was mainly influenced by its main TAGs, whereas apparently minor components did not develop a crucial role. Furthermore, we also used the polymorphic behavior of natural fat and oils (virgin and extra virgin olive oil, and Iberian ham fat) as a tool to determine authenticity (different ham categories depending on the fattening system used) and detection of adulterations (fraudulent additions of hazelnut oil in olive oil). The combined use of DSC and preliminary chemometric calculations permitted determining fraudulent additions of raw hazelnut oil in an extra virgin olive oil (Arbequina) at concentrations below 5%. On the other hand, highly significant differences were detected in the polymorphic behavior of Iberian ham fat from the bellota and cebo categories.

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Books on the topic "Polymorphism (crystallography)"

1

Bernstein, Joel. Polymorphism in molecular crystals. Oxford: Oxford University Press, 2007.

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G, Brittain H., ed. Polymorphism of pharmaceutical solids. 2nd ed. New York: Informa Healthcare, 2009.

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G, Brittain H., ed. Polymorphism in pharmaceutical solids. New York: M. Dekker, 1999.

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Smolegovskiĭ, A. M. Istorii︠a︡ izuchenii︠a︡ poliformizma: Khimicheskiĭ aspekt : istorii︠a︡ izuchenii︠a︡ allotropii ugleroda. Moskva: In-t istorii estestvoznanii︠a︡ i tekhniki RAN, 2010.

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Sebastian, M. T. Random, non-random, and periodic faulting incrystals. Yverdon: Gordon and Breach, 1994.

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P, Krishna, ed. Random, non-random, and periodic faulting in crystals. Yverdon, Switzerland: Gordon and Breach Science Publishers, 1994.

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Liquid Polymorphism. Wiley, 2013.

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Rice, Stuart A., H. Eugene Stanley, Aaron R. Dinner, and Pablo Debenedetti. Liquid Polymorphism. Wiley & Sons, Incorporated, John, 2013.

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Rice, Stuart A., H. Eugene Stanley, Aaron R. Dinner, and Pablo Debenedetti. Liquid Polymorphism. Wiley & Sons, Incorporated, John, 2013.

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Rice, Stuart A., H. Eugene Stanley, Aaron R. Dinner, and Pablo Debenedetti. Liquid Polymorphism. Wiley & Sons, Incorporated, John, 2013.

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Book chapters on the topic "Polymorphism (crystallography)"

1

Ochsenbein, Philippe, and Kurt J. Schenk. "Crystallography for Polymorphs." In Polymorphism, 139–66. Weinheim, FRG: Wiley-VCH Verlag GmbH & Co. KGaA, 2006. http://dx.doi.org/10.1002/3527607889.ch6.

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Kwokal, Ana. "Preparation, Stabilisation and Advantages of Metastable Polymorphs." In Engineering Crystallography: From Molecule to Crystal to Functional Form, 247–60. Dordrecht: Springer Netherlands, 2017. http://dx.doi.org/10.1007/978-94-024-1117-1_14.

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"Crystallography and Polymorphism." In Structure and Properties of Fat Crystal Networks, Second Edition, 19–44. CRC Press, 2012. http://dx.doi.org/10.1201/b12883-2.

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"- Crystallography and Polymorphism." In Structure and Properties of Fat Crystal Networks, 20–45. CRC Press, 2012. http://dx.doi.org/10.1201/b12883-3.

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Southern, Scott A., and David L. Bryce. "Recent advances in NMR crystallography and polymorphism." In Annual Reports on NMR Spectroscopy, 1–80. Elsevier, 2021. http://dx.doi.org/10.1016/bs.arnmr.2020.10.001.

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Glazer, A. M. "3. Crystal structures." In Crystallography: A Very Short Introduction, 39–63. Oxford University Press, 2016. http://dx.doi.org/10.1093/actrade/9780198717591.003.0003.

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‘Crystal structures’ describes the different types of close packing—hexagonal, cubic, face-centred cubic, and body-centred cubic—used to describe many simple inorganic structures, especially those of the elements. The reason for atoms to pack so closely together is to form the densest array possible to provide a stable structure. The ability of a chemical substance to adopt different crystal structures is called polymorphism, as displayed by carbon. Examples of simple inorganic structures, such as common salt, are explained along with organic crystal structures, and the different methods of crystal growth. Crystallography has also played a major part in determining the structures and activities of large biological molecules like DNA, RNA, proteins, and viruses.

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Sánchez-Férez, Francisco, and Josefina Pons. "Polymorphism and Supramolecular Isomerism: The Impasse of Coordination Polymers." In Crystallization [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96930.

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The chapter presented hereafter, outlines the narrow link between chemistry and crystallography that impelled the identification of polymorphism and provided a priceless grounding to understand structure-properties relationship. It was initially conceived for organic substances but actually embraced by metal–organic products, especially in the study of coordination polymers. All of the technologic advances have provided profound insights on the control of crystal structures formation revealing that any applied stimulus over a substance can undergo a structural transformation. This has led to the implementation of several methodologies in the industrial and academic segment shedding light on the source of hitherto, not well understood results.

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"Solid-State NMR Spectroscopic/X-Ray Crystallographic Investigation of Conformational Polymorphism/Pseudopolymorphism in Crystalline Stable and Labile Hydrated Drugs." In Symmetry, Spectroscopy, and Crystallography, 189–204. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2015. http://dx.doi.org/10.1002/9783527684199.ch12.

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Giacovazzo, Carmelo. "Phasing methods for powder data." In Phasing in Crystallography. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199686995.003.0017.

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Powder diffractometry plays (and will probably continue to play in the near future) a central role in research and technology, because it allows us to investigate materials which are not available as a single crystal of adequate size and quality. Therefore, recently, much effort has been devoted to the development of powder diffraction. Improvements include the design of better instruments (e.g. optimized synchrotron radiation lines, time-of-flight technology at pulsed neutron sources, optics, generators, detectors), as well as more sophisticated methods for data analysis. As a result, in favourable cases, high quality powder patterns of proteins may be collected which contain sufficient information to allow identification of the unit cell and of the space group, a result unthinkable 30 years ago. This has opened the way for qualitative analysis and study of the polymorphism of macromolecules (Margiolaki et al., 2005; Collings et al., 2010). Advances in the experimental and the theoretical aspects of powder crystallography have been able to reduce losses of information from a powder pattern with respect to single crystal data, and have made ab initio crystal structure solution from powder experiments possible. The reader may deduce the increasing popularity of powder techniques from: (i) Table 1.11, where, among the CSD (Cambridge Structural Database), entries on 1 January 2012, 2354 powder diffraction studies were counted; (ii) Figure 12.1, where the cumulative statistics (up to the year 2006) on the number of structures solved via powder diffraction data is shown (SDPD database); (iii) Figure 12.2, where the statistics on the number of studies in the ICDD (Inorganic Crystal Structure Database) (to the year 2005) for different types of data is given. For the powder case, 21 472 cases are counted for which powder data have been used, mostly for refinement purposes. In this chapter, we will neglect experimental aspects, unless unrelated to the phasing problem. We will describe in Sections 12.2 to 12.5, the basic features of powder pattern diagrams, and in Sections 12.6 and 12.7, the procedures for full pattern indexing and space group determination. Ab initio phasing will be treated in Section 12.8 and non-ab initio methods in Section 12.9. The combination of anomalous dispersion techniques with powder methods is postponed to Section 15.9.

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"Thermoanalytical and Crystallographic Methods." In Polymorphism in Pharmaceutical Solids, 330–58. CRC Press, 2018. http://dx.doi.org/10.3109/9781420073225-12.

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Conference papers on the topic "Polymorphism (crystallography)"

1

Kumar, Naveen, Davender Singh, Parveen Kumar, and Jitendra Gangwar. "Crystallographic representation of polymorphs ZrO2 using VESTA software." In ADVANCES IN BASIC SCIENCE (ICABS 2019). AIP Publishing, 2019. http://dx.doi.org/10.1063/1.5122493.

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Amita, Asha, Vishakha, Neetu, Davender Singh, Naveen Kumar, Rajesh Kumar, and Jitendra Gangwar. "Crystallographic representation of Patterson densities of polymorphs α-Fe2O3." In 3RD INTERNATIONAL CONFERENCE ON CONDENSED MATTER AND APPLIED PHYSICS (ICC-2019). AIP Publishing, 2020. http://dx.doi.org/10.1063/5.0001735.

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Siroha, Piyush, Davender Singh, Rakhi Soni, and Jitendra Gangwar. "Comparative study on crystallographic representation of transition metal oxides polymorphs nanomaterials using VESTA software: Case study on Fe2O3 and TiO2." In NATIONAL CONFERENCE ON RECENT ADVANCES IN EXPERIMENTAL AND THEORETICAL PHYSICS (RAETP-2018). Author(s), 2018. http://dx.doi.org/10.1063/1.5051294.

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