Phase Behavior of Diglycerol Monomyristate in Different Nonpolar Organic Solvent Systems

We have investigated the phase behavior of diglycerol monomyristate (DGM) in a variety of organic solvents over a wide range of temperatures and compositions. At lower temperature, there exists a surfactant solid, which solubilize different amounts of oils depending on the oil nature. The melting temperature of the solid phase is virtually constant in a wide range of composition. In all the systems, a lamellar liquid crystal (L_α) is formed in surfactant‐rich regions at intermediate temperatures between the solid‐melt and isotropic two‐ or single‐phase regions. In the dilute regions reverse vesicles are formed in the L_α+O regions mainly in the case of linear hydrocarbon type oils. In the aromatic and cyclic aliphatic oils, there are isotropic solutions at 25°C. However, there is dispersion of α‐solid in the case of liner hydrocarbon oils. Two liquid‐phase regions above the L_α phase are observed in the case of tetradecane and hexadecane. In the shorter chain oil systems, such as octane and decane, no two liquid‐phase appear above L_α region. That is the two liquid‐phase region is largely dependent on the chain length of the oils, and becomes wider in longer hydrocarbon oil.     

Kinetics and Mechanism of Cetyltrimethylammonium Bromide Catalyzed N-Bromosuccinimide Oxidation of D-Mannose in Acidic Medium

The kinetics and mechanism of N-bromosuccinimide (NBS) oxidation of D-mannose in the absence and presence of cetyltrimethylammonium bromide (CTAB) in acidic media have been studied under the condition [D-mannose]_T ? [NBS]_T at 40°C. Under the kinetic conditions, both the slower uncatalyzed and faster catalyzed paths go on. Both the paths show the fractional and first order dependence on [D-mannose] and [NBS]_T, respectively. The rate decreased with increase in acidity. Neither succinimide (NHS) nor Hg(II) influenced the reaction rate. Activation parameters of the reactions were determined by studying the reaction at different temperatures (30–50°C). The influence of salts on the reaction rate was also studied. CTAB accelerates the reactions and the observed effects have been explained by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. In the reaction, approximately 1 mole of NBS oxidized one mole of D-mannose. A reaction scheme of the oxidation of D-mannose by NBS was found to be in consistent with the rate law and the reaction stoichiometry.     

Flexoelectric response at defect sites in nematic inversion walls

Electric field experiments have been carried out on +1 and ?1 defects formed in alignment inversion walls, in a planarly aligned nematic phenyl benzoate. The results show that the defects are non‐singular in the core and exhibit a flexoelectric response to an applied d.c. or low frequency a.c. field. When the c‐director flux lines are circular, as in a +1 defect in a wall parallel to the easy axis, flexoelectro‐optic switching characterized by an azimuthal angle variation is observed. When the c‐director flux is radial, the response is seemingly through polar angle variations involving no rotation of the extinction brushes due to crossed polarizers. This conclusion follows from the field‐induced structural distortions observed at a ?1 defect having a combination of radial and tangential c‐director fields.     

Gradient flexoelectric switching response in a nematic phenyl benzoate

We report on the inverse flexoelectric effects observed in a nematic liquid crystal with a small positive dielectric anisotropy subject to static and very low frequency (<1 Hz) a.c. fields. The Bobylev–Pikin flexobands appear at a temperature‐dependent d.c. threshold. Under square wave excitation, a new type of transient optical response occurs soon after each polarity reversal, and we ascribe it to the gradient flexoelectric distortion explicable on the basis of the presence of intrinsic double layers. This instability is characterized by a threshold voltage that decreases with temperature. Its maximum amplitude increases linearly with voltage close to threshold, and occurs after polarity reversal at a time τ_m that scales inversely as the voltage; τ_m decreases exponentially with frequency and temperature. After each polarity change, the ionic current following the charging current decreases almost exponentially to a non‐zero value; the residual current increases monotonically with the applied bias.     

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.