Silica Chloride Nano Particle Catalyzed Ring Opening of Epoxides by Aromatic Amines

Silica chloride nano particle (nano SiO₂‐Cl), has been found to be heterogeneous catalyst for facile, simple and mild ring opening of epoxides with aromatic amines to afford β‐amino alcohols in dry CH₂Cl₂ at room temperature.     

Novel cationic surfactant ion pair based solid phase microextraction fiber for nano-level analysis of BTEX

Ion pair of cationic surfactant (cetytrimethylammonium bromide) and tungestosilicic acid incorporated in PVC matrix, was used for coating a piece of copper wire as a new high sensitive SPME fiber in extraction and determination of BTEX compounds from the headspace of water samples prior to GC/FID analysis. Under optimum extraction conditions, limits of detection for benzene, toluene, ethylbenzene, p-xylene, m-xylene and o-xylene were found to be 1.18, 5.61, 0.87, 0.29, 0.22 and 0.33 ng L(-1) respectively. Low detection limits, wide linear dynamic ranges, good reproducibility (RSD% 1.48-4.27), high fiber capacity and high mechanical durability are some of the most important advantages of the new fiber.     

Synthesis of Pyrazolo[3,4‐d]pyrimidin‐4‐ones Catalyzed by Br?nsted‐acidic Ionic Liquids as Highly Efficient and Reusable Catalysts

A convenient and efficient method for the synthesis of pyrazolo[3,4‐d]pyrimidin‐4‐ones via heterocyclization reaction of 5‐amino‐1H‐pyrazole‐4‐carboxamides with triethyl orthoesters using two Br?nsted‐acidic ionic liquids, 3‐methyl‐1‐(4‐sulfonic acid)butylimidazolium hydrogen sulfate [MIM⁺(CH₂)₄SO₃H][HSO₄^?] or N‐(4‐sulfonic acid)butyl triethylammonium hydrogen sulfate [Et₃N⁺(CH₂)₄SO₃H][HSO₄^?], as efficient homogeneous catalysts under solvent‐free conditions is described.     

Recent advances in phase matching of second‐order nonlinearities in monolithic semiconductor waveguides

Techniques used to assist phase matching of second‐order nonlinearities in semiconductor waveguides are reviewed. The salient points of each method are highlighted, with their strengths and weaknesses with regard to various key applications discussed. Recent progress in these techniques is also reviewed. Emphasis is placed on two techniques, namely quasi‐phase matching via domain disordering utilizing quantum well intermixing, and exact phase matching using Bragg reflection waveguides.     

Quantitation of atorvastatin in human plasma using directly suspended acceptor droplet in liquid-liquid-liquid microextraction and high-performance liquid chromatography-ultraviolet detection

A simple and sensitive methodology based on liquid-liquid-liquid microextraction (LLLME) followed by high-performance liquid chromatography-ultraviolet detection (HPLC-UV) has been successfully developed for the determination of atorvastatin (AT) in human plasma. AT was first extracted from 4.5 mL acidic aqueous sample (diluted plasma, donor phase, pH 1) at temperature 45 °C through 400 μL 1-octanol for 4.5 min, while being agitated by a stirring bar at 1250 rpm. Then, a 5.5 μL free suspended basic aqueous droplet (acceptor phase, pH 10) was delivered to the top-center position of the organic membrane. The mixture was stirred at 650 rpm for 7.5 min and the analyte was back-extracted into the droplet. Finally, the acceptor phase was taken into a microsyringe and injected directly into the HPLC. An enrichment factor of 187 along with substantial sample clean up was obtained under the optimized conditions. The calibration curve showed linearity in the range of 1-500 ng mL⁻¹ with regression coefficient corresponding to 0.996. Limits of detection (S/N = 3) and quantification (S/N = 10) were 0.4 and 1 ng mL⁻¹, respectively. A reasonable relative recovery (91%) and satisfactory intra-assay (4.4-7.0%, n = 6) and inter-assay (4.9-7.7%, n = 8) precision illustrated good performance of the analytical procedure. This technique was eventually applied for the determination of AT in human plasma after oral administration of 40 mg single dose of drug. The protocol proved to be highly cost-effective and reliable for the screening purpose.     

Solution thermodynamics and preferential solvation of hesperidin in aqueous cosolvent mixtures of ethanol,isopropanol, propylene glycol,and n-propanol

The solubility of hesperidin in some {cosolvent (1) + water (2)} mixtures expressed in mole fraction at temperatures from 293.15 K to 333.15 K reported by Xu et al. has been used to calculate the apparent thermodynamic functions, Gibbs energy, enthalpy, and entropy, of the dissolution processes by means of the van’t Hoff and Gibbs equations. Non-linear enthalpy–entropy relationships were observed for this drug in the plots of enthalpy vs. Gibbs energy of dissolution with positive or negative slopes regarding mixtures composition and/or cosolvent. Moreover, the preferential solvation of hesperidin by the cosolvents was analysed by using the inverse Kirkwood–Buff integrals observing that this drug is preferentially solvated by water in water-rich but preferentially solvated by cosolvents in mixtures 0.20 (or 0.24) ≤ x₁° ≤ 1.00. Furthermore, a new mathematical model was proposed for correlating/predicting the solubility of hesperidin in binary solvent mixtures at various temperatures.     

Novel Complexes of Zinc(II) with Different Proton Transfer Ion Pairs Obtained from Dipicolinic Acid: Synthesis, Characterization and X-ray Crystal Structure

Abstract  Three new complexes of zinc(II) with three different proton transfer compounds, obtained from pyridine-2,6-dicarboxylic acid (dipicolinic acid) and different Lewis bases, were synthesized and characterized using IR, ¹H NMR and ¹³C NMR spectroscopy and single crystal X-ray diffraction. The chemical formulae and space groups of the complexes are (pipzH₂)[Zn(pydc)₂] · 4H₂O, P2₁/n (1), (EDGnH₂)[Zn(pydc)₂] · 3H₂O, P2₁/c (2) and (pdaH₂)[Zn(pydc)₂] · 4H₂O, (3) where pydc, pipz, EDGn and pda are standing for dipicolinic acid, piperazine, ethylenediguanidine and 1,3-propanediamine respectively. Cell parameters of the complexes are a = 7.9493(4) ?, b = 13.4386(7) ?, c = 21.0557(11) ?, β = 90.415(5)° for 1; a = 9.785(3) ?, b = 25.671(4) ?, c = 9.3402(16) ?, β = 90.790(17)° for 2 and a = 8.411(5) ?, b = 11.650(7) ?, c = 12.793(8) ?, α = 115.534(9)°, β = 92.791(10)°, γ = 97.778(10)° for 3. The three crystal structures illustrate that the metal ion is six-coordinated by two pydc’s. In all three compounds a large number of O–H⋯O, N–H⋯O and C–H⋯O hydrogen bonds are observed. These interactions as well as other noncovalent interactions such as ion–pairing and π–π stacking play an important role in the formation and stabilization of supramolecular systems in the crystal lattices. Index Abstract  The main purpose of this paper is to report and discuss about the synthesis, characterization, crystal structure and non-covalent interactions of three supramolecular frameworks of six-coordinated Zn(II) complexes, obtained by the reaction of different proton transfer compounds, i.e. (pipzH₂)(pydc), (EDGnH₂) (pydc) · 3H₂O and (pdaH₂)(pydc) · (pydcH₂) · 2.5H₂O with corresponding metallic salts.      

Further calculations on solubility of dipyrone in some binary solvent mixtures at various temperatures

The recently reported solubility data of dipyrone in binary solvent mixtures of {ethanol + water}, {methanol + ethanol} and {methanol + 1-propanol} at various temperatures have been used to report further numerical results based on the Jouyban–Acree model.