Authors:Buchi Reddy Vaddula, Swathi Yalla, and Michael A. Gonzalez
A simple and rapid one-step continuous-flow synthesis route has been developed for the preparation of chromene derivatives from the reaction of aromatic aldehydes, α-cyanomethylene compounds, and naphthols. In this contribution, a one-step continuous-flow protocol in a ThalesNano H-Cube Pro™ has been developed for the preparation of these chromene derivatives. This arises from the multicomponent one-step reaction of aromatic aldehydes, α-cyanomethylene compounds, and naphthols. This flow protocol was optimized in 2-methyltetrahydrofuran, which is a more environmentfriendly solvent. The faster residence times (<2 min) coupled with elevated pressure (∼25 bar) results in an efficient, safer, faster, and modular reaction. Results obtained illustrate that this base-catalyzed reaction affords the respective chromene derivative products in very high yields. The products can then be easily purified by recrystallization, if desired.
Authors:J. Van den Brande, Ilse Weuts, G. Verreck, J. Peeters, M. Brewster, and G. Van den Mooter
Thermal analysis was performed on the anti-HIV agent loviride in order to test its suitability to be processed using hot-melt
extrusion. Temperature characteristic parameters of crystallization were determined to quantify the stability of amorphous
loviride. The present study has shown that cooling and heating loviride at different rates influenced its thermal stability.
At high cooling rates melted loviride did not crystallize during cooling, and formed a glass that recrystallized during reheating.
Very low cooling rates resulted in significant decomposition of the drug. The glass transition temperature was found to increase
as a function of increasing heating rates and the activation energy for the transition from the glassy to the super-cooled
liquid state was relatively high, indicating good stability of the glass.
Authors:Lucinéia de Carvalho, Milena Segato, Ronaldo Nunes, Csaba Novak, and Éder Cavalheiro
The thermal decomposition behavior of acesulfame-K (ACK), aspartame (ASP), sodium cyclamate (SCL), saccharine (SAC), and sodium
saccharine (SSA) were investigated. After re-crystallization of the commercial samples the compounds were characterized by
using elemental analysis, IR spectroscopy and thermoanalytical techniques (TG/DTG, DTA, and DSC). Evidences of hydrate water
loss were observed for SSA and ASP. Melting was detected for SSA and SAC. Each compound decomposed in a characteristics way.
The decomposition of APS and SAC took place completely, while ACK, SCL and SSA resulted in K2SO4, Na2SO4, and Na2SO4, as residues respectively. The Flynn-Wall-Ozawa method for kinetic calculations was applied for the volatilization of saccharine
resulting in Ea = 80 ± 1 kJ mol−1 and log A = 7.36 ± 0.07 min−1.
Authors:T. Tsukame, M. Kutsuzawa, H. Sekine, H. Saitoh, and Y. Shibasaki
A forensic sample consisting of melt-recrystallized polymers that was recovered from the scene of a fire in a factory was identified by differential scanning calorimetry. The factory commonly used two kinds of film sheets, A and B, made by different manufacturers. It was necessary to decide whether the forensic sample related to material A or B. The forensic sample and reference samples of materials A and B were subjected to infrared spectroscopy and pyrolysis gas chromatograph mass spectrometry measurements, which revealed their polyethylene nature. The thermal behaviour of the samples was examined by differential scanning calorimetry (DSC) and they were found to be blends of two kinds of polyethylenes, low-density polyethylene and linear low-density polyethylene. The samples could be identified and distinguished from each other via the DSC measurements.
Authors:Felicitász Velledits, János Csizmeg, and Anna Oravecz-Scheffer
The Little Plain Basin is one of the largest units in the Pannonian Basin System. Its continuation in Slovakia is called the Danube Basin. The Little Plain Basin is one of the most underexplored areas in Hungary. Based on archival geologic and geophysical data the lithostratigraphic composition of the area is controversial. The significance of the area is increased by the known Neogene and the supposed basement (Paleozoic and Mesozoic) hydrocarbon systems in Hungary and in Slovakia.
The purpose of this study is to identify the exact age, facies, geologic formations and possible source rocks of the Triassic section penetrated by the Gyõrszemere-2 well in the Little Plain Basin.
Based on new facies and paleontological results it can be stated that two Triassic sequences are identified in the well, separated by fault breccia. A carbonate sequence was deposited between the Induan and Early Anisian and above that a homogeneous recrystallized dolomite appears, the age of which is unknown.
The following formations were encountered, from base upward:
Arács Marl Fm. (3,249.5–3,030 m), silty marl with ooids, bivalves, gastropods and ostracode shells. Occasionally layers of angular quartz grains in large quantities appear. Postcladella kahlori and Spirobis phlyctaena indicates Induan (Early Triassic) age.
Köveskál Dolomite Fm. (3,030–2,790 m), rich in ooids and also containing anhydrite. The Glomospira and Glomospirella dominance indicates an age interval between Olenekian and earliest Anisian age.
Fault breccia (2,790–2,690 m) separating the Köveskál and overlying dolomites.
Upper dolomite (2,690–2,200 m): homogeneous, saccharoidal, and totally recrystallized. The age is unknown.
The low TOC values of the supposed source rock interval (marl between 3,249.5 and 3,030 m) indicate poor hydrocarbon potential.
A new method is presented to analyze the irreversible melting kinetics of polymer crystals with a temperature modulated differential
scanning calorimetry (TMDSC). The method is based on an expression of the apparent heat capacity,
. The present paper experimentally examines the irreversible melting of nylon 6 crystals on heating. The real and imaginary
parts of the apparent heat capacity showed a strong dependence on frequency and heating rate during the melting process. The
dependence and the Cole-Cole plot could be fitted by the frequency response function of Debye's type with a characteristic
time depending on heating rate. The characteristic time represents the time required for the melting of small crystallites
which form the aggregates of polymer crystals. The heating rate dependence of the characteristic time differentiates the superheating
dependence of the melting rate. Taking account of the relatively insensitive nature of crystallization to temperature modulation,
it is argued that the ‘reversing’ heat flow extrapolated to ω → 0 is related to the endothermic heat flow of melting and the
corresponding ‘non-reversing’ heat flow represents the exothermic heat flow of re-crystallization and re-organization. The
extrapolated ‘reversing’ and ‘non-reversing’ heat flow indicates the melting and re-crystallization and/or re-organization
of nylon 6 crystals at much lower temperature than the melting peak seen in the total heat flow.
Authors:Daniel Plano, Elena Lizarraga, Juan Antonio Palop, and Carmen Sanmartín
four types of thermal behavior for the series A and B:
• Behavior I Compounds that do not alter the thermal behavior after an initial fusion–recrystallization cycle ( Fig. 1 ). Under these conditions there is no evidence of polymorphic behavior. The
Authors:M. D. Baró, N. Clavaguera, S. Bordas, M. T. Clavaguera-Mora, and J. Casas-Vázquez
The kinetics of bulk crystallization of Se61.5Ge15 4Sb23.1 glasses was investigated from their thermal behaviour. In the thermal characterization of a glass the recrystallization temperature is highly dependent on both the rate of heating and the thermal history of the glass. Vitreous samples were prepared by quenching. From ratedependent curves it was found that the recrystallization process obeys first-order kinetics with an apparent activation enthalpy of 48±5 kcal/mole. Further analysis allows determination of both the activation enthalpy,H=90±4 kcal/mole, and the kinetic exponent of the Avrami equation,n=1.9±0.3.
Authors:R. Ceolin, V. Agafonov, A. Gonthier-Vassal, H. Szwarc, J. Cense, and Ph. Ladure
Flutamide usually crystallizes in the orthorhombic non-centrosymmetric space group Pna21 (from I) and melts atTfus=384 K with ΔfusH=30 kJ·mol−1. It may be obtained in the glassy state (Tg=272 K) by quenching the melt. Although evidence of polymorphism could not be obtained by means of crystallography, DSC studies
of the recrystallization process indicate that a metastable form (form II) occurs first and is transformed into the stable
form at room temperature. ΔH for the transition I→II (2.52 kJ·mol−1) is close to the difference in energy (about 2 kJ·mol−1) calculated for the two possible conformers of flutamide.
The kinetics of solute segregation to partial dislocations in a Cu–3.4 At.% Sb alloy was studied by using a phenomenological approach with differential scanning calorimetry and isothermal calorimetry. The material, severely deformed by repeated bending, presented an excess of dissociated edge dislocations with a dislocation density amounting to about 8.5·1014 m–2, calculated using a prior model of the authors, together with calorimetric recrystallization trace analysis. The kinetics was found to be ruled by two overlapping mechanisms: diffusion of solute atoms mostly through dislocation pipes in the initial and middle stages of the reaction process, acting together with bulk solute diffusion in these stages and later. Bulk solute diffusion increases as the reaction proceeds, as shown by the increasing values of apparent activation energy in the reaction. The exponent of the Mehl-Johnson-Avrami equation used in the phenomenological description was successfully fitted to a time—temperature-dependent function, increasing in agreement with the apparent activation energy behaviour, as may be expected.