Some recent studies of the mechanisms of dehydration reactions of solids

Galwey, Andrew K.

doi:10.1007/bf02109111

Cited by 27 publications

(8 citation statements)

References 18 publications

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“…There is an extensive body of literature available on the dehydration of inorganic materials which may be used to aid in the interpretation of these results. [20][21][22][23] Generally, three products of dehydration can be distinguished: (i) the crystal lattice is virtually identical with that of the original hydrate, (ii) an amorphous phase is produced, or (iii) the dehydrated residue crystallizes to give a new product. 20 A recent article by Petit and Coquerel 21 considers in detail how the water molecules are released and the possible subsequent reorganization of the newly formed anhydrous material.…”

Section: Discussionmentioning

confidence: 99%

Characterization of the Phase Transitions of Trehalose Dihydrate on Heating and Subsequent Dehydration

Taylor

York

1998

Journal of Pharmaceutical Sciences

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Many pharmaceutical compounds of interest form hydrates. The phase behavior of different particle size fractions of trehalose dihydrate was studied as the sugar was dehydrated by heating. Hot-stage microscopy, X-ray powder diffraction, thermogravimetric analysis, and differential scanning calorimetry were used to characterize the phase changes. Small particles (<45 microm) formed an amorphous phase on dehydration and subsequently liquefied at temperatures above the glass transition temperature of amorphous trehalose. Crystallization to the anhydrate was observed from this supercooled liquid. Large particles (>425 microm) underwent a solid-solid conversion from the dihydrate to the anhydrate at temperatures as low as 80 degrees C. This solid-solid conversion was explained by a catalytic effect of the liberated dihydrate water on the rearrangement of the dehydrated phase to the anhydrate. The large surface area-to-volume ratio of the small particles resulted in dehydration prior to attaining the threshold temperature for rearrangement, explaining why solid-solid conversion was absent for these particles.

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Section: Discussionmentioning

confidence: 99%

Characterization of the Phase Transitions of Trehalose Dihydrate on Heating and Subsequent Dehydration

Taylor

York

1998

Journal of Pharmaceutical Sciences

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“…The remaining energy is thought to derive from the energy balance of subsequent, faster side reactions between the products. It is thought likely that reaction (23) takes place in two stages (24) (25) .CH3 + CH3N02 -CH4 + aCHzN02…”

Section: The Thermal Decomposition Of Liquid Nitromethanementioning

confidence: 99%

The study of decomposition reactions through the exchange of thermal energy

Constantinou

1994

Int J of Chemical Kinetics

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In many decomposition reactions, the reaction velocity can be described as a product of two functions: a temperature dependent part K ( T ) and the kinetic function f(1 -a), where T designates the temperature and a the fraction of reactant that has decomposed. The physical interpretation of these functions is discussed for both solid and homogeneous systems. A method is described by which f (1 -a ) and K ( T ) can be determined from kinetic data. The mechanism of decomposition can subsequently be identified which should be consistent with the derived kinetic parameters. The method has been applied to analyze the kinetics of the thermal decomposition of nitromethane.

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“…The thermal process probably happens because of gradual release of water from interlayer planes or channels. Reorganization begins in the inner part of each particle without loss of crystallinity [19,20]. Heated crystals undergo chemical degradation, which was confirmed by the darkening of crystals.…”

Section: Thermomicroscopic Investigationsmentioning

confidence: 89%

Thermal and X-ray analysis of racemic bupivacaine hydrochloride

Sykuła

Łodyga-Chruścińska

Pałecz

et al. 2011

J Therm Anal Calorim

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An amide-type local anesthetic drug, bupivacaine hydrochloride (BupiHCl), in the form of racemate is listed in the European and American pharmacopoeias and continues to be used in medicine. Thermal and X-ray analysis of commercial BupiHCl monohydrate was performed by differential scanning calorimetry with thermogravimetry, hot stage microscopy, and X-ray diffraction. Endothermic dehydration occurs at the temperature range of 73-130°C for DSC-TG 111 (Setaram) and at 83-150°C for DSC 404 (Netzsch). Both curves at 2 and 10°C min -1 clearly reflect phase transformation of anhydrous Form I into II before reaching the melting point. A well-defined exothermic phase transition of BupiHCl was detected at a lower heating rate. Temperature-resolved X-ray diffraction in conjunction with DSC led to determining a similarity between the obtained thermal events. Microscopic investigation also confirmed the above-mentioned transformations.

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Some recent studies of the mechanisms of dehydration reactions of solids

Cited by 27 publications

References 18 publications

Characterization of the Phase Transitions of Trehalose Dihydrate on Heating and Subsequent Dehydration

Characterization of the Phase Transitions of Trehalose Dihydrate on Heating and Subsequent Dehydration

The study of decomposition reactions through the exchange of thermal energy

Thermal and X-ray analysis of racemic bupivacaine hydrochloride

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