pH‐Sensitive methacrylic acid–methyl methacrylate copolymer Eudragit L100 and dimethylaminoethyl methacrylate,butyl methacrylate,and methyl methacrylate tri‐copolymer Eudragit E100

Poly (methyl methacrylate) derivatives such as Eudragit are largely used for drug encapsulation and in controlled oral drug delivery. With special focusing on those applications, solubilization and precipitation conditions of two pH‐sensitive Eudragit polymers, namely, L100 and E100, were investigated via systematic studies. Effects of various physicochemical parameters such as pH, polymer concentration, salinity, buffer concentration, and incubation time on the solubilization and precipitation of these polymers were investigated. In addition, pH titration of both polymers was reported. Considering both macroscopic and quantitative aspects such as the final mean particle size, size distribution, morphology, and the zeta potential, it was established that the different precited parameters could not be dissociated and exert a synergic action on the solubilization and precipitation of both polymers. Titration curves revealed two equivalences that helped estimating carboxylic content of Eudragit L100 (6 mmol/g) and ammonium content of Eudragit E100 (4 mmol/g). In this study, the solubilization and the precipitation domains were for the first time clearly established by considering the above‐mentioned parameters. Moreover, it was found that Eudragit L100 and E100 cannot be considered as classic polyelectrolytes; in fact, solubilization and precipitation domains were not affected by ionic strength.     

Experimental and theoretical study on the regioselective bis- and polyalkylation of 2-mercaptonicotinonitrile and 2-mercaptopyrimidine-5-carbonitrile derivatives

The synthetic utility of 2-mercaptonicotinonitriles 3 and 4, as well as 2-mercapto-4-oxo-6-phenyl-1,4-dihydropyrimidine-5-carbonitrile 20 as building blocks for novel bis- and poly(pyridines), along with poly(pyrimidines) via alkylation with the corresponding bis- and poy(halo) compounds was investigated. Spectroscopic and theoretical studies confirmed the S-alkylation rather than the N-alkylation.     

Reassignment of the structures of condensation products of α-keto α′-formylarylhydrazones with ethyl cyanoacetate: a novel route to ethyl 5-arylazo-2-hydroxynicotinates

The condensation of α-keto α′-formylarylhydrazones with ethyl cyanoacetate afforded ethyl 5-arylazo-2-hydroxy-6-aryl (or alkyl) nicotinates. The structures of the reaction products could be established based on X-ray crystal structure determination.     

Textural,structural and catalytic properties of zirconia doped by heteropolytungstic acid: a comparative study between aerogel and xerogel catalysts

Zirconia doped by heteropolytungstic acid HPW have been synthesized by sol–gel method using two drying techniques of the solvent evacuation. Samples were analyzed with adsorption–desorption of N₂ at 77 K, and the aerogel catalyst was found to exhibit a higher surface area and a higher average pore diameter compared to xerogel. XRD results show that aerogel develops ZrO₂ tetragonal phase, whereas xerogel is amorphous. The thermal analysis studies show that the aerogel’s thermal stability is better than the xerogel one. The catalytic behavior of the aerogel and xerogel toward the nature of the isomerization products probably depends on the acidity and the presence of carbide species. This has been explained by XPS and isopropanol dehydration reaction. In fact, the deconvolution aerogel’s Cls bands reveals the presence of four carbon species assigned to C–C, C=O, C–O and carbide species.     

Unleashing a Microcomputer in the Laboratory,Part III

Experimental Techniques -     

Transient stress and interfacial area generated during breakup of a Newtonian thread immersed in a Newtonian medium

The transient stress and the transient average orientation generated by the breakup process of a long Newtonian filament imbedded in a quiescent Newtonian viscous liquid have been calculated. Rayleigh disturbances were used to describe the relaxation of the filament and the variation of interfacial area in the absence of flow during the course of disintegration process. The effect of viscosity ratio and initial radius of the filament were discussed. It was demonstrated that the predictions of the model in terms of the time-evolution of interfacial area can be used to select the best conditions for carrying out the breaking thread experiments. The predictions of the proposed model were compared to some experimental data on polyamide/polyethylene system.     

Geometries,stabilities, electronic and magnetic properties of small PdnIr (n = 1–8) clusters from first-principles calculations

The geometrical structures, relative stabilities, electronic and magnetic properties of small Pd_nIr (n = 1–8) clusters have been systematically investigated using density functional theory at the B3PW91 level. The optimised geometries show that the lowest-energy structures of Pd_nIr clusters prefer a three-dimensional configuration. The relative stability of these clusters was examined by analysis of the binding energies per atom, fragmentation energies, the second-order difference of energies and the HOMO–LUMO energy gaps as a function of cluster size. The obtained results exhibit that the Pd₂Ir, Pd₃Ir and Pd₅Ir clusters are more stable than their neighbouring clusters. The energy gap of the Pd₂Ir cluster is the largest of all the clusters (2.258 eV). In addition, the charge transfers, vertical ionisation potentials, vertical electron affinities and chemical hardness were calculated and discussed. The magnetism calculations indicate that the total magnetic moment of Pd_nIr clusters is mainly localised on the iridium atom for Pd_1–6Ir clusters. Meanwhile, the 5d orbital plays the key role in the magnetic moment of the iridium atom.     

Reactions with Hydrazonoyl Halides 611: Synthesis of 2,3-Dihydro-1,3,4-Thiadiazoles

2-[1,2-Diaza-3-(2,3-dimethyl-5-oxo-1-phenyl(3-pyrazolin-4-yl))prop-2-enylidene]-3-phenyl-5-substituted 1,3,4-thiadiazolines and 2-{[4-(2,3-dimethyl-5-oxo-1-phenyl(3-pyrazolin-4-yl))(1,3-thiazol-2-yl)]cyanomethylene}-3-phenyl-5-substitu- ted 1,3,4-thiadiazolines were synthesized from hydrazonoyl halides and 4-{-2-aza-2-[(methylthiothioxomethyl)amino]vinyl}-2,3-dimethyl-1-phenyl-3-pyrazoin-5-one and 2-[4-(2,3-dimethyl-5-oxo-1-phenyl-3-pyrazolin-4-yl)-1,3-thiazol-2-yl]ethane-nitrile, respectively. All synthesize compounds were elucidated by elemental analysis, spectra, and alternative synthesis routes, whenever possible.     

Crystal structure,Hirshfeld surface analysis,vibrational properties,and electrical and dielectric studies of the bis (4-benzylpyridinium) tetrachlorocuprate (II)

The present paper undertakes the study of (C₁₂H₁₂N)₂CuCl₄, which is a new hybrid compound. It is synthesized and characterized by single-crystal X-ray diffraction, Hirshfeld surface analysis, and FT-IR, FT-Raman, and impedance spectroscopies. It is crystallized in the monoclinic system with C2/c space group. Its crystal structure was determined and refined down to an R value of 0.05 and a wR value of 0.14. The structure can be described by the alternation of two different, cationic–anionic layers parallel to (110) plan. This complex is assembled into 3D supramolecular architecture by hydrogen bonds (N–H…Cl, C–H…Cl) and π–π interactions. Hirshfeld surface analyses and fingerprint plots are used for decoding intermolecular interactions in the crystal network and contribution of component units for the construction of the 3D architecture. The presence of different functional groups and the nature of their vibrations were identified by FT-IR and FT-Raman spectroscopies. The material is characterized by impedance spectroscopy technique measured in 209–500 MHz frequency and 296–390 K temperature ranges. In addition, the Cole–Cole (Z? versus Z?) plots were well fitted to an equivalent circuit built up by a parallel combination of resistance (R) and constant phase elements (CPEs). The close values of activation energies obtained from the analysis of equivalent circuit data confirm that the transport is through ion hopping mechanism in the bis (4-benzylpyridinium) tetrachlorocuprate.