Anhydrous Crystals Research Articles

Effects of Temperature and Humidity History on Brittleness of α-Sulfonated Fatty Acid Methyl Ester Salt Crystals.

α-Sulfonated fatty acid methyl ester salts (MES), which were made from vegetable sources, are attractive candidates for eco-friendly washing detergents because they have various special features like excellent detergency, favorable biodegradability, and high stability against enzymes. To overcome some disadvantages of powder-type detergents like caking, sorting, and dusting, we studied how temperature and humidity history, as a model for long-term storage conditions, can affect crystalline structures and reduce the brittleness of MES powder. We characterized the crystalline structure of MES grains using small-angle X-ray scattering, wide-angle X-ray scattering, differential scanning calorimetry, and Fourier transform infrared spectroscopy measurements and determined the yield values, which measure the brittleness of MES grains, in shear stress using dynamic viscoelasticity measurements. This study confirmed that MES crystals form three pseudo-polymorphs via thermal or humidity conditioning: metastable crystals (αsubcell), anhydrous crystals (β subcell), and dihydrate crystals (β' subcell). Further, we found that the yield value increases upon phase transition from the β subcell to the β' subcell and from the β' subcell to the αsubcell. Therefore, controlling the thermal and humidity conditioning of MES grains is an effective way to decrease the brittleness of MES powders and can be used to overcome the above mentioned disadvantages of powder-type detergents in the absence of co-surfactants.

Conformational adjustments over synthons of urea and thiourea based assemblies

Conformational adjustments in 1-(n-methylthiazol-2-yl)-3-naphthalen-1-yl-thiourea (n = 4, 5) through carbon–nitrogen bond rotation over an intramolecular hydrogen bonded synthon were established. Isosteric homodimeric hydrogen bonded synthons were analysed in their respective self-assemblies. The corresponding urea derivatives, namely, 1-(n-methylthiazol-2-yl)-3-naphthalen-1-yl-urea (n = 4, 5) also had similar homodimeric sub-assemblies in each of their respective assemblies. However, these two positional isomers of a urea derivative did not show polymorphism, which was observed in the corresponding thiourea counterpart. On the other hand, 1-(5-methylthiazol-2-yl)-3-naphthalen-1-yl-thiourea underwent a facile cyclisation reaction, whereas 1-(5-methylthiazol-2-yl)-3-naphthalen-1-yl-urea formed hydrated salts upon reaction with different inorganic acids. Self-assembly of chloride salt had a bifurcated hydrogen bond between two N–H of the urea moiety with chloride ion, whereas perchlorate salt had a similar bond with the oxygen atom of a water of crystallization, making a difference in the type of heterosynthon. Thus, heterosynthons of these salts were found to be anion dependent. Each salt has a cation differing in conformational adjustments guided by anions. Multi-component hydrated and anhydrous crystals of 1-(5-methylthiazol-2-yl)-3-naphthalen-1-yl-urea with tetrabutylammonium chloride were formed concomitantly. These are examples of anion-guided assemblies of thiazole based compounds containing a neutral host. The different naphthyl group orientations of the heterosynthon resulted in two polymorphic hydrated cocrystals.

From isomorphous to “anisomorphous” ionic co-crystals of barbituric acid upon dehydration and return

The isomorphous hydrated ionic co-crystals (ICCs) of barbituric acid (BA) of the formula BA·MBr·2H2O (M = Na, K, Rb) can be easily dehydrated to the corresponding anhydrous ICCs BA·MBr (M = Na, K, Rb). The three anhydrous crystals possess different structures that revert to the isomorphous crystals upon hydration. Only BA·RbBr is stable in air, making it possible to determine its crystal structure from single-crystal X-ray diffraction. BA·NaBr and BA·KBr rapidly absorb water from air and convert to the hydrated form. The crystal structures of BA·NaBr and BA·KBr have been determined by X-ray powder diffraction in sealed capillaries. Solid-state NMR spectroscopy was fundamental in determining the number of independent molecules in the asymmetric unit for the structural determination of the ICC BA·NaBr. The dehydration process was characterized by variable temperature X-ray powder diffraction, DSC and TGA.

Homochiral crystal generation via sequential dehydration and Viedma ripening

1,2-Bis(N-benzoyl-N-methylamino)benzene (2) forms centrosymmetric hydrate crystals (2·xH2O) and non-centrosymmetric anhydrous crystals. Dehydration of this hydrate (30 min at 140 °C) resulted in the formation of chiral crystals (i.e. a physical racemate of the conglomerate crystals) as verified using solid-state circular dichroism and powder X-ray diffraction. Subsequent attrition-enhanced deracemization, also known as Viedma ripening, was used to obtain homochiral crystals of 2 within 5 h.

Role of Lipid Blooming and Crystallite Size in the Performance of Highly Soluble Drug-Loaded Microcapsules

Hot-melt coating is of growing interest, because it does not require solvents, resulting in reduced process times and costs. However, excipients for this technology are mainly triacylglycerides (TAGs) or their derivatives, which exhibit polymorphism, surface disruption, and complex crystallite networks, affecting the release profile of produced microcapsules. In this work, anhydrous citric acid crystals were coated with molten tristearin using conventional inlet air temperatures (microcapsules A) and temperatures above the melting point of α-form (microcapsules B). Additionally, microcapsules A were tempered to achieve polymorphic stability (microcapsules AB). The product yield and coating efficacy were above 90% and 97%, respectively, demonstrating the feasibility and efficacy of the process. Small angle X-ray scattering analysis confirmed that the tristearin shell of microcapsules B is in the β-form with a larger average crystallite size than microcapsules A and AB. Scanning electron microscopy images revealed a nonbloomed surface of microcapsules B. We showed that blooming does not play a critical role in the drug release, but the apparent diffusion coefficient of drug is dramatically reduced by increasing TAGs crystallite size and resulting tortuosity. This work brings new insights on the micrometric properties of solid lipid dosage forms, being an important step to prevent the overuse of excipients with unknown toxicity.

Vibrational Spectroscopy and Phonon-Related Properties of the L-Aspartic Acid Anhydrous Monoclinic Crystal.

The infrared absorption and Raman scattering spectra of the monoclinic P21 l-aspartic acid anhydrous crystal were recorded and interpreted with the help of density functional theory (DFT) calculations. The effect of dispersive forces was taken into account, and the optimized unit cells allowed us to obtain the vibrational normal modes. The computed data exhibits good agreement with the measurements for low wavenumbers, allowing for a very good assignment of the infrared and Raman spectral features. The vibrational spectra of the two lowest energy conformers of the l-aspartic molecule were also evaluated using the hybrid B3LYP functional for the sake of comparison, showing that the molecular calculations give a limited description of the measured IR and Raman spectra of the l-aspartic acid crystal for wavenumbers below 1000 cm(-1). The results obtained reinforce the need to use solid-state calculations to describe the vibrational properties of molecular crystals instead of calculations for a single isolated molecule picture even for wavenumbers beyond the range usually associated with lattice modes (200 cm(-1) < ω < 1000 cm(-1)).

“Guanigma”: The Revised Structure of Biogenic Anhydrous Guanine

Living organisms display a spectrum of wondrous colors, which can be produced by pigmentation, structural coloration, or a combination of the two. A relatively well-studied system, which produces colors via an array of alternating anhydrous guanine crystals and cytoplasm, is responsible for the metallic luster of many fish. The structure of biogenic anhydrous guanine was so far believed to be the same as that of the synthetic one, a monoclinic polymorph (denoted as α). Here we re-examine the structure of biogenic guanine, using detailed experimental X-ray and electron diffraction data, exposing troublesome inconsistencies, namely, a “guanigma”. To address this, we sought alternative candidate polymorphs using symmetry and packing considerations and then utilized first-principles calculations to determine whether the selected candidates could be energetically stable. We identified theoretically a different monoclinic polymorph (denoted as β), were able to synthesize it, and confirmed using X-ray diffractio...

Biologically active flavonoids from Dodonaea viscosa and their structure–activity relationships

Antioxidant and anticholinesterase activities of twelve flavonoids i.e. santin (1), penduletin (2), viscosine (3), 6,7-dimethylkaempferol (4), kaempferol-​3-​methylether (5), 3,4′-dimethoxy-5,7-dihydroxyflavone (6), 5,7,4′-trihydroxy-3′-(3-hydroxymethylbutyl)-3,6-dimethoxyflavone (7), 5,7-dihydroxy-3′-(2-hydroxy-3-methyl-3-butenyl)-3,6,4′-trimethoxy-flavone (8), 5,7-dihydroxy-3′-(3-hydroxy-methylbutyl)-3,6,4′-trimethoxyflavone (9), 5,7-dihydroxy-3′-(4′′-acetoxy-3′′-methylbutyl)-3,6,4′-trimethoxy flavone (10), aromadendrin, (2S,3S) 3,4′,5,7-tetrahydroxyflavanone (11), and pinocembrin (12), together with monohydrated crystal (1A) of 1 and anhydrous crystal (3A) of 3 – isolated from Dodonaea viscosa – were studied. The results are given as 50% inhibition concentrations (IC50). Their structure–activity relationships are discussed for both activities. Flavonoids 3 and 10 showed higher antioxidant activity in all tests. 3 Also showed moderate acetylcholinesterase (IC50: 182.97±1.25μM) and significant butyrylcholinesterase (IC50: 47.07±0.54μM) inhibitory activities. Compounds 2 (IC50: 55.78±1.01μM) and 3A (IC50: 58.72±1.02μM) were also moderate anticholinesterase agents against butyrylcholinesterase enzyme. Monohydrate crystal (1A) showed better antioxidant and anticholinesterase activities than its amorphous form (1). In contrast, the amorphous 3 exhibited better activity than the anhydrous crystal (3A). In hydrous crystal, the water molecule might be responsible for better activity. These natural flavonoids can be used as pharmaceuticals and/or preservatives in respective industries.

Effect of Sonication, Liquid Nitrogen Cooling During Crystal Growth and Heating Process on Crystal Growth of Paclitaxel Coated on a FullyBioabsorbable Poly (L-Lactic acid) Stent

To achieve appropriate efficacy of paclitaxel (PTX) used in drug eluting stents, uniform PTX coating on the stent and increased initial release of PTX leading to immediate therapeutic level of the drug are required. The present study investigated whether either restriction of crystal growth though sonication and subsequent liquid nitrogen cooling, or formation of anhydrous PTX crystals through heating microcrystals after seeding and crystal growth could increase PTX initial release coated on a fully-bioabsorbable poly(L-lactic acid) stent. The sonication and subsequent liquid nitrogen cooling of the growing PTX crystals could prevent stable attachment of the crystals onto the stent surface. In addition, the initial PTX release from the stent applied sonication during the crystal growth process followed by heating showed five times as high as the stent without heating, which indicated the heating improved the PTX release from the stent at early phase. These results suggested that PTX was changed into an anhydrous soluble form.

Phase Transformation between Anhydrate and Monohydrate of Sodium Dehydroacetate

The crystal structures of monohydrate and anhydrous substance were determined from the single crystals for the first time. The phase transformation between anhydrate and monohydrate of sodium dehydroacetate was in situ investigated by using Raman spectroscopy. The mechanism of the phase transformation was proposed. The results showed that the monohydrate crystalline phase of sodium dehydroacetate can transform to anhydrous phase through solid–solid transformation upon heating or solution-mediated phase transformation. From powder X-ray diffraction (PXRD) patterns and thermal gravimetric analysis (TGA) data, it was found that the anhydrous crystals obtained by these two methods are the same in structure. However, the scanning electron microscopy (SEM) results revealed that the surface of the anhydrous sodium dehydroacetate crystals obtained by high-temperature dehydration was much rougher than that obtained by solution-mediated phase transformation. Furthermore, the dynamic vapor sorption (DVS) results sho...

On the existence of “l-arginine acetamide”

We argue that the “l-arginine acetamide” crystal reported by Anitha et al. (J Therm Anal Calorim 119:785–789, 2015) is actually the well-known monoclinic form of anhydrous l-arginine hydrochloride crystal.

Multiphase model for hygrothermal analysis of porous media with salt crystallization and hydration

A new fully coupled multiphase model for hygrothermal analysis and prediction of salt diffusion and crystallization in porous building materials is presented. The relative humidity, the temperature, the concentration of the dissolved salt and the concentration of precipitated salts are assumed as independent variables. A suitable modelling of the crystallization/dissolution and hydration/dehydration processes allows considering salts with hydrous and anhydrous crystals. Some numerical applications on fired-clay bricks show the effectiveness of the proposed approach.

Origins of hydration differences in homochiral and racemic crystals of aspartic acid.

The propensity for crystalline hydrates of organic molecules to form is related to the strength of the interactions between molecules, including the chiral composition of the molecular solids. Specifically, homochiral versus racemic crystalline samples can exhibit distinct differences in their ability to form energetically stable hydrates. The focus of the current study is a comparison of the crystal structures and intermolecular forces found in solid-state L-aspartic acid, DL-aspartic acid, and L-aspartic acid monohydrate. The absence of experimental evidence for the DL-aspartic acid monohydrate is considered here in terms of the enhanced thermodynamic stability of the DL-aspartic acid anhydrate crystal as compared to the L-aspartic acid anhydrate as revealed through solid-state density functional theory calculations and terahertz spectroscopic measurements. The results indicate that anhydrous DL-aspartic acid is the more stable solid, not due to intermolecular forces alone but also due to the improved conformations of the molecules within the racemic solid. Hemihydrated and monohydrated forms of DL-aspartic acid have been computationally evaluated, and in each case, the hydrates produce destabilized aspartic acid conformations that prevent DL-aspartic acid hydrate formation from occurring.

Optical trapping assembling of clusters and nanoparticles in solution by CW and femtosecond lasers

Laser trapping of molecular systems in solution is classified into three cases: JUST TRAPPING, EXTENDED TRAPPING, and NUCLEATION and GROWTH. The nucleation in amino acid solutions depends on where the 1064-nm CW trapping laser is focused, and crystallization and liquid–liquid phase separation are induced by laser trapping at the solution/air surface and the solution/glass interface, respectively. Laser trapping crystallization is achieved even in unsaturated solution, on which unique controls of crystallization are made possible. Crystal size is arbitrarily controlled by tuning laser power for a plate-like anhydrous crystal of l-phenylalanine. The α- or γ-crystal polymorph of glycine is selectively prepared by changing laser power and polarization. Further efficient trapping of nanoparticles and their following ejection induced by femtosecond laser pulses are introduced as unique trapping phenomena and finally future perspective is presented.

Crystallization of sodium sulfate in porous media by drying at a constant temperature

Sodium sulfate is generally seen as one of the most destructive salts in the weathering of historical objects. The crystallization which causes the damage can either be induced by drying and/or cooling of a salt solution in a porous material. In this study we have studied the crystallization of sodium sulfate during the drying of various porous materials at different temperatures. The experiments were conducted such that the Peclet number was smaller than one, i.e., the ion transport in the porous material is dominated by diffusion. The results show that at temperatures above 22 °C during the drying the anhydrous crystal phase of sodium sulfate, i.e., thenardite is eventually formed. Below 22 °C heptahydrate crystal phase is formed, which is metastable with respect to the corresponding mirabilite solubility.

Inside Cover: Insights into the Crystallisation Process from Anhydrous, Hydrated and Solvated Crystal Forms of Diatrizoic Acid (Chem. Eur. J. 3/2015)

Inside Cover: Insights into the Crystallisation Process from Anhydrous, Hydrated and Solvated Crystal Forms of Diatrizoic Acid (Chem. Eur. J. 3/2015)

Stability Conditions and Mechanism of Cream Soaps: Effect of Polyols.

Fatty acids, fatty acid potassium soaps, polyols and water are essential ingredients for producing stable cream soaps. The solution behavior of the above four components system has been studied to elucidate the effect of four sorts of polyols (glycerol, 1,3-butylene glycol, polyethylene glycol 400 and dipropylene glycol) on the stability of cream soaps. It has been revealed that the lamellar liquid crystalline one-phase converted to a two-phase of a lamellar phase and an isotropic aqueous solution by the addition of a few percent of 1,3-butylene glycol, polyethylene glycol 400 and dipropylene glycol, whereas the lamellar one-phase was remained by about 50 wt% of glycerol in the aqueous solution. The X-ray data at room temperature showed that the existence of 1:1 acid soap (1:1 mole ratio of potassium soap/fatty acid) crystals in the 1,3-butylene glycol, polyethylene glycol 400 and dipropylene glycol systems, whereas that the coexistence of 1:1 acid soap crystal and a lamellar gel phase (swelled lamellar gel structure) in the glycerol system. The phase transition peaks from coagel to gel (Tgel) and from gel to liquid state (Tc) were appeared in the above four polyol systems by DSC measurements. It was confirmed from the combined data of SAXS and DSC that the existence of anhydrous 1:1 acid soap gels (or with small amount of bound water) in the all polyol systems, whereas the coexistence of the anhydrate gel and the swelled gel with a lot of intermediate water in the only glycerol system. This swelled gel structure would be contributed to stabilize the dispersed anhydrate acid soap crystals in cream soaps.

Thermal and X-ray Diffraction Analysis of Lactose Polymorph

Different preparation methods and techniques were utilized to explore the crystallization behavior of the anhydrous lactose crystals prepared from α-lactose monohydrate. The crystal morphology of the obtained polymorphs was observed by SEM and the structural characterization of the samples was carried out by XRD. And several typical crystal shapes have obtained in the experiment, such as tomahawks, diamond-shaped plates and pyramids. The anhydrous α-lactose form obtained by rapid dehydration exhibits the same X-ray peaks as the monohydrate. The presence of lactose polymorphs in the test samples was determined by DSC and the weight loss was measured by TGA. This study supplied some methods to prepare the anhydrous lactose and discovered a dehydration peak of β-lactose in the TGA picture at approximately 125°C.

Screening and Characterization of Hydrate Forms of T-3256336, a Novel Inhibitor of Apoptosis (IAP) Protein Antagonist.

Different crystal packing of hydrates from anhydrate crystals leads to different physical properties, such as solubility and stability. Investigation of the potential of varied hydrate formation, and understanding the stability in an anhydrous/hydrate system, are crucial to prevent an undesired transition during the manufacturing process and storage. Only one anhydrous form of T-3256336, a novel inhibitor of apoptosis (IAP) protein antagonist, was discovered during synthesis, and no hydrate form has been identified. In this study, we conducted hydrate screening such as dynamic water vapor sorption/desorption (DVS), and the slurry experiment, and characterized the solid-state properties of anhydrous/hydrate forms to determine the most desirable crystalline form for development. New hydrate forms, both mono-hydrate and hemi-hydrate forms, were discovered as a result of this hydrate screening. The characterization of two new hydrate forms was conducted, and the anhydrous form was determined to be the most desirable development form of T-3256336 in terms of solid-state stability. In addition, the stability of the anhydrous form was investigated using the water content and temperature controlled slurry experiment to obtain the desirable crystal form in the crystallization process. The water content regions of the stable phase of the desired form, the anhydrous form, were identified for the cooling crystallization process.

Análise de operações de cross hedge para o mercado de açúcar cristal no Brasil

The aim of this study is to evaluate whether cross hedging with futures contracts of Brazilian hydrous and anhydrous ethanol American would be an effective tool against unwanted movements in the prices of sugar, given the absence of a future contract for producers of crystal sugar in the period 2010-2012. Four weekly series were built for the estimation of the optimum ratio and effectiveness of cross hedge. Through the variances and covariances obtained with the estimation of VAR (Vector Autoregressive) model matrix, we obtained the optimum ratio and the effectiveness of the operation of cross hedge. The optimal ratio between the cross hedge future of Brazilian hydrated ethanol and sugar was approximately 2%, but the operation was not effective. As for the cross hedge between American anhydrous ethanol and Brazilian sugar crystal, the optimal ratio was approximately 19%, and the effectiveness of the operation was of 2%, showing to be somewhat more effective, but it is not enough to protect the agents from the physical market of Brazilian sugar crystal. Keywords: cross hedging with Brazilian hydrous and anhydrous American ethanol, spot market of crystal sugar, effectiveness.