Phase Transitions in Some Hydrogen-Bonded Molecules

Abdel‐Kader, M. M.; Gwaily, S.E.; Zayat, Marcos

doi:10.1002/1521-396x(200205)191:1<49::aid-pssa49>3.0.co;2-e

Cited by 7 publications

(4 citation statements)

References 17 publications

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“…During heating, form I directly transformed to form III, not form II as reported in the literature. [19][20][21] The transformation mechanism of form I f III included two steps. In the first step, the transformation started at the surfaces of form I crystals, probably due to epitaxial nucleation and growth of form III crystals on the surfaces of form I crystals.…”

Section: Discussionmentioning

confidence: 99%

“…The transformation temperatures were reported, respectively, at 99 and 81 °C, and the phase transformation was thought to be form I f II. Moreover, the properties of form I crystals such as the electrical properties 20 and calorimetric parameters 21 were measured as a function of temperature. Results showed that all these properties had marked changes in behavior around 81 °C, which was believed to be the phase transformation from form I f II.…”

Section: Introductionmentioning

confidence: 99%

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Mechanism and Kinetics of the Polymorphic Transformation of o-Aminobenzoic Acid

Jiang

Jansens

Horst

2010

Crystal Growth & Design

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A polymorphic transformation can have an undesirable influence on the product quality during the processing and storage of polymorphic compounds in the industry. By understanding the mechanism and kinetics of the polymorphic transformation, the polymorphism can be better controlled and the product quality can be improved. The transformation of o-aminobenzoic acid (o-ABA) polymorphs in air was studied at high temperature. With the aid of Raman spectroscopy, accurate calibration lines among three polymorphs of o-ABA were constructed, which facilitate the determination of the polymorphic content during the transformation processes. The transformation process of form I was in situ monitored at 90 °C using Raman spectroscopy and optical microscopy. During the heating, form I transforms to form III, not to form II as previously reported. This phase transformation proceeds through two steps:(1) rapid nucleation and crystal growth of form III on the crystal surfaces of form I, and then (2) slow transformation via a vapor-mediated transformation. Form II also converts into form III at 90 °C, but proceeds only via the vapor-mediated transformation. The results show that at higher temperature form III is the most stable form, while form I and form II are metastable.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mechanism and Kinetics of the Polymorphic Transformation of o-Aminobenzoic Acid

Jiang

Jansens

Horst

2010

Crystal Growth & Design

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“…For instance, the scattered intensity in the high frequency spectral region has been used to extract information about some of the molecular dipolemultipole polarizability tensor components of several isotropic molecules such as CH 4 , CF 4 , CCl 4 and SF 6 [1][2][3][4][5] and of anisotropic molecules belonging to symmetry group C 2v or D ∞h (N 2 ) [6,7]. The special case of very light molecules H 2 and D 2 has also been investigated [8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

High Frequency Interaction-Induced Anisotropic Rototranslational Light Scattering Spectra of Gaseous Carbon Dioxide

2011

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The anisotropic rototranslational scattering of carbon dioxide gas is studied theoretically at 294.5 K, in the frequency range 10-470 cm −1 , at a density of 1.026254 mole/litre. The anisotropic double differential cross-section for scattered light is calculated theoretically using new site-site Morse-Morse-Morse-spline-van der Waals intermolecular potentials with the parameters fitted to the different thermophysical and transport properties. Our theoretical calculations take into account multipole contributions from the first-and second-order dipole-induced dipole, first-order dipole-induced octopole and first-order dipole-dipole-quadrupole light scattering mechanisms as well as their cross contributions. The irreducible spherical form for the induced operator of these light scattering mechanisms was determined. The high frequency wings are discussed in terms of the collision-induced rotational Rayleigh effect and estimates for the dipole-octopole polarizability E 4 , is obtained and checked with the ab initio theoretical value. Good agreement is obtained at moderate frequencies between the theoretical and experimental spectra. When an exponential contribution exp(−ν/ν 0 ), with ν 0 = 115 cm −1 is considered to model very short-range light scattering mechanism, good agreement is found over the whole frequency range.

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“…Over the last several years, and also at present, our research program is centered on the investigation of phase transition in some organic, inorganic and/or complex compounds [1][2][3][4][5][6][7] through the study of their electrical, calorimetric and/or thermal parameters at different temperatures. Most of the investigated compounds are hydrogen-bonded in their crystalline states.…”

Section: Introductionmentioning

confidence: 99%