Synthesis and properties of α-sulfo carboxyl disodium salt

The synthesis and properties of α-sulfo carboxyl disodium salt (SCDS) were studied in detail for the first time in this paper. SCDS was synthesized via saponification reaction of fatty acid methyl ester sulfonate sodium (MES). FT-IR was used to characterize the molecular structure of target product. The yield of disodium salt was greater than 98% by two-phase titration. The performance of SCDS was studied and was compared with raw materials MES, conventional anionic surfactant AES and nonionic surfactant AEO₉. The result shows SCDS can reduce the surface tension of the solution to 27.89?mN/m at critical micelle concentration (CMC). The wetting ability of SCDS was significantly enhanced with the increase of temperature. The emulsification effect of SCDS on the soybean oil is better than that on the liquid paraffin. Surprisingly, SCDS has a good foamability and foaming stability.     

Amperometric Glucose Determination by Means of Glucose Oxidase Immobilized on a Cellulose Acetate Film: Dependence on the Immobilization Procedures

Glucose microelectrodes were prepared by immobilizing glucose oxidase onto a cellulose acetate film coating a platinum wire. Hexamethylenediamine (HMDA) and Glutaraldehyde (GA) were employed as spacer and coupling agent, respectively. Sensitivities and linear response ranges were studied as a function of the relative amounts of HMDA and GA. The best sensitivity was found when HMDA and GA were 5% and 2.5% in aqueous solutions, respectively. Taking as a reference the functioning of this biosensor, the roles of HMDA and GA percentages appear to be opposed when the extension of the linear response range is considered. Indeed, an increase of one unit in HMDA percentage (from 5 to 6 %) induces an increase in the extension of the linear response range equal to that obtained with a decrease of one unit of GA percentage (from 2.5 to 1.5%).     

Aziridines—XVI: Etude des conformations privilegiees cycle aromatique-petit cycle dans les C-aryl aziridines N-non-substituees

The preferred conformation of phenyl-2 aziridine involves the phenyl ring nearly bisecting the plane of the small ring (maximum conjugation). As the steric hindrance due to substituents on the aromatic ring is more substantial, the aromatic ring moves towards a perpendical plane. Good agreement between experimental (IR and NMR) and theoretical studies of the syn-anti configurational equilibrium of NH in these compounds is demonstrated. The analysis of the total electronic populations clarifies an understanding of the variation of the charge transfer small ring?aromatic cycle as a function of the aromatic nucleus.     

Soliton dynamics in alternating trans-polyacetylene and in stacked systems

The influence of substitutional disorder, of random forces and of energy dissipation on solitons in alternating trans-polyacetylene using the Su-Schrieffer-Heeger Hamiltonian is discussed. Double ionization in polyene chains was also investigated. Further soliton dynamics within a full Pariser-Parr-Pople Hamiltonian for trans-polyacetylene are presented. The presence of conformational solitons in stacked systems is shown numerically in a polyformamide model system. Possible relations to DNA and carcinogenesis are briefly reviewed.     

Stereoselectivity and chiral recognition in copper(I) olefin complexes with a chiral diamine

Trigonal copper(I) complexes of the chiral bidentate ligand (1S,2S)-N,N'-Bis-(mesitylmethyl)-1,2-diphenyl-1,2-ethanediamine ((S,S)-1) have been prepared with hydrocarbon olefins, as well as with allylic alcohols and ethers. The stereochemistry of the complexes has been investigated by 1H NMR spectroscopy and by combined quantum mechanics and molecular mechanics (QM/MM) computational methods. The coordinated chiral nitrogen atoms can display equal (R, R) or opposite (R, S) configuration, the latter being disfavored if steric hindrance is present above and below the coordination plane. Although the complexes exist as rapidly equilibrated mixtures of stereoisomers, one of these is often dominant, and prochiral olefins are coordinated with high enantioface selection. In addition, the [(S,S)-1]-Cu+ fragment selectively recognizes the R enantiomer of secondary allylic alcohols and ethers, as confirmed by the X-ray crystal structure analysis of the adduct with (R)-1-buten-3-ol. The reasons for the observed selectivities have been elucidated, and lead to some implications which are consistent with the enantioselection observed in catalytic cyclopropanation reactions promoted by copper complexes of the same ligand.     

Studies on the V2O5?TiO2 system, V. Equilibrium pressures

The oxygen equilibrium pressures from pure V₂O₅ and co-precipitated V₂O₅–TiO₂ system were measured in the range of 200–450 °C. The behavior of the equilibrium pressure with changes of temperature of the samples with and without TiO₂ is attributed to Ti⁴⁺ interaction with the V₂O₅ lattice.

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V₂O₅ - V₂O₅–TiO₂ 200–450°C. TiO₂ Ti⁺⁴ V₂O₅.

     

Double resonance observation of the (2ν3, E) state in methane

By using the double resonance technique we have observed the infrared inactive (2ν₃, E) level in methane. The experimental value of the vibrational energy (6043.8 cm^?1) is in good agreement with recent calculations based on the “local mode” model.     

Sodium ibuprofen dihydrate and anhydrous

(R,S)-(±)-ibuprofen sodium salt (racemate) dihydrate (SID) was dehydrated and the physicochemical properties of SID and the anhydrous forms (SIA) were compared by different analytical techniques (scanning electron microscopy, helium pychnometry, differential scanning calorimetry, X-ray powder diffractometry). The dehydration of SID, followed by thermogravimetry in isothermal conditions, allowed to calculate the activation energy of the dehydration process and to predict the mechanism of dehydration. Dehydration occurred in one step and the activation energy was rather low, indicating the ease of water removal from the crystal. The mechanism of dehydration followed a three dimensional diffusion (Jander equation). Similarly to the dehydration, the hydration process was followed under isothermal conditions by exposing the anhydrous powder at 64% RH at different temperatures. The mechanism of hydration was governed by a two dimensional diffusion and the energy associated to the process was very low, indicating the ease of crystal hydration. The driving force for the hydration is higher than that for the dehydration. From a thermodynamic point of view this fact may explain why the hydrated form is more stable than the anhydrous one. Solubilities, determined at different temperatures in water and in phosphate buffer (pH 6.8), showed that SID is more soluble in water than SIA for temperatures higher than approximately 283 K. On the contrary, in phosphate buffer SIA is always more soluble than SID in the temperature range considered for the experiments. Drug release reflects the solubility in water and phosphate buffer previously reported.