Induced G phase through intermolecular hydrogen bonding: X. Crystallization kinetics study on two structural isomers

A comparative systematic crystallization kinetics study has been carried out on two distinct novel liquid crystalline isomers, DBA:R:DBA and DBA:H:DBA (where DBA = p-n-decyloxybenzoic acid, R = resorcinol and H = hydroquinone) using differential scanning calorimetry. The kinetics experiment is performed from the crystal G phase (kinetophase), which is a common induced phase in both compounds. The molecular mechanism and dimensionality of crystal growth are studied from the Avrami exponent n while the characteristic crystallization time (t ^*) at each crystallization temperature is deduced from the individual plots of log t vs. Δ H.     

Synthesis of Thermally Stable Energetic 1,2,3‐Triazole Derivatives

Various thermally stable energetic polynitro‐aryl‐1,2,3‐triazoles have been synthesized through Cu‐catalyzed [3+2] cycloaddition reactions between their corresponding azides and alkynes, followed by nitration. These compounds were characterized by analytical and spectroscopic methods and the solid‐state structures of most of these compounds have been determined by using X‐ray diffraction techniques. Most of the polynitro‐bearing triazole derivatives decomposed within the range 142–319 °C and their heats of formation and crystal densities were determined from computational studies. By using the Kamlet–Jacobs empirical relation, their detonation velocities and pressures were calculated from their heats of formation and crystal densities. Most of these newly synthesized compounds exhibited high positive heats of formation, good thermal stabilities, reasonable densities, and acceptable detonation properties that were comparable to those of TNT.     

Novel domino reactions for the efficient synthesis of 5,6-dihydro-1,4,2-oxathiazines

A facile efficient synthesis of novel 3-aryl-5,6-dihydro-1,4,2-oxathiazin-6-ols from the reaction of (E)-N-hydroxyarylimidoyl chlorides and 1,4-dithiane-2,5-diol in the presence of triethylamine is described. This transformation presumably proceeds via in situ generation of 2-mercaptoacetaldehyde and nitrile oxide and their concomitant [3+3] annulation.     

Fluorimetric estimation of U(VI) in the presence of a large excess of Th(IV)

A fluorescence based method has been developed for the determination of trace amounts of uranium in thorium matrix using a mixture of phosphoric acid (H₃PO₄) and sulfuric acid (H₂SO₄), as fluorescence enhancing reagent for uranyl (UO₂ ²⁺) ion fluorescence. Synthetic samples mimicking the composition of ThO₂ fuel were prepared and the concentration of U(VI) was estimated. Satisfactory results are obtained when uranium is present at a concentration of 10 ppm in solid thorium samples with good precision.     

Structural interaction leading to volumetric changes in aqueous solutions of nitrates of rubidium,cesium, strontium,yttrium, and gallium at different temperatures

Densities of the aqueous dilute solutions of rubidium, cesium, strontium, yttrium, and gallium nitrate were measured at different temperatures ranging from (293.15–343.15) K and atmospheric pressure. From these density values, the apparent molal volumes were calculated and fitted to Masson’s correlation and the temperature dependence was correlated by a second order polynomial. The apparent molal volumes at infinite dilution and experimental slopes have been interpreted in terms of ion–solvent and ion–ion interactions, respectively. The measurements include density as per ASTM D-4052, refractive index (nD²⁵) at sodium D line at 25 °C. Thermal isobaric expansibility was calculated and structure making and structure breaking behaviour of electrolytes were inferred from the sign of the second derivative of apparent molal volumes with respect to temperature at constant pressure. The experimental apparent molal volume was compared with the available literature value.     

Quality by design: A systematic and rapid liquid chromatography and mass spectrometry method for eprosartan mesylate and its related impurities using a superficially porous particle column

The present work describes the systematic development of a robust, precise, and rapid reversed‐phase liquid chromatography method for the simultaneous determination of eprosartan mesylate and its six impurities using quality‐by‐design principles. The method was developed in two phases, screening and optimization. During the screening phase, the most suitable stationary phase, organic modifier, and pH were identified. The optimization was performed for secondary influential parameters—column temperature, gradient time, and flow rate using eight experiments—to examine multifactorial effects of parameters on the critical resolution and generated design space representing the robust region. A verification experiment was performed within the working design space and the model was found to be accurate. This study also describes other operating features of the column packed with superficially porous particles that allow very fast separations at pressures available in most liquid chromatography instruments. Successful chromatographic separation was achieved in less than 7 min using a fused‐core C₁₈ (100 mm × 2.1 mm, 2.6 μm) column with linear gradient elution of 10 mM ammonium formate (pH 3.0) and acetonitrile as the mobile phase. The method was validated for specificity, linearity, accuracy, precision, and robustness in compliance with the International Conference on Harmonization Q2 (R1) guidelines. The impurities were identified by liquid chromatography with mass spectrometry.     

Box–Behnken Design-Based Development and Validation of a Reverse-Phase HPLC Analytical Method for the Estimation of Paclitaxel in Cationic Liposomes

Chromatographia - Stability-indicating reverse-phase HPLC analytical method for the quantification of Paclitaxel (PTX) in the bulk and cationic liposomes was developed. The optimized method was...     

Investigation of chemical space networks using graph measures and random matrix theory

Journal of Mathematical Chemistry - Large collections of molecules (chemical libraries) are nowadays routinely screened in the process of designing drugs for specific ailments. Chemical and...     

β-Cyclodextrin-based chiral nanocomposite for thin-layer chromatographic detection of enantiomers of fluoxetine

Enantioselective analysis or separation is very essential for improved therapeutic effects of drugs as the pure enantiomeric drug formulations display potential benefits over racemates. In this work, we carried out (i) the synthesis of a nanocomposite of β-cyclodextrin and 3D graphene (G/β-CD NC), and (ii) its application for the detection of fluoxetine enantiomers [(RS)-FLX)] using a thin-layer chromatographic method. The synthesized nanocomposite was introduced into silica gel slurry while preparation of thin-layer plates. The separation conditions were optimized by altering pH, temperature, and mobile phase composition. The method is simple and easy to be optimized, and it can therefore be exploited to assess and monitor routine work of enantiomeric purity of drug enantiomers. The average precision (as measured by RSD) was in the region of 1.35‒1.65% for the enantiomers of (RS)-FLX. The measured limit of detection and limit of quantification for (RS)-FLX enantiomers were 1.8 and 5.4 mg mL^‒1, respectively.