Biphasic epoxidation of 1-octene with H2O2 catalyzed by amphiphilic fluorinated Ti-loaded zirconia

A series of amphiphilic fluorinated zirconia containing titanium was prepared by titanium impregnation followed by fluorination and alkylsilylation of zirconium oxide. Physical properties of the resulting samples were characterized by XRD analysis, UV-vis spectroscopy, BET surface area analysis and EDAX analysis. The effects of fluorine and alkylsilane groups on the samples were studied by the epoxidation of 1-octene with aqueous hydrogen peroxide. The epoxidation of alkenes is one of the most important methods of functionalizing simple hydrocarbons. The amphiphilic fluorinated catalysts were more active and more efficient than the conventional titania-silica and zirconia-silica mixed oxides in linear alkene epoxidation; enhanced by the presence of alkylsilane and fluorine groups in the catalysts. Modification with alkylsilane successfully induces the hydrophobic behavior of zirconia which is hydrophilic in nature; whereas fluorine was chosen for its electron-withdrawing effect which further activates the titanium active sites.     

ASSOCIATION PHENOMENON OF A MIXED CATIONIC SURFACTANT IN NON-AQUEOUS SYSTEM

Pseudoternary phase diagrams of a mixture of two cationic surfactants, hexan-1-ol and a third component consisting of glycerol, formamide, water/glycerol or water/formamide were obtained. These diagrams were then contrasted with its water counterpart.

The results showed that the association phenomenon were entirely different from that of the corresponding water system. The lamellar liquid crystalline region was absent in both of the glycerol or formamide systems. This indicated a less ordered or destabilizing effect in the association structure resulting in the replacement water with that of glycerol or formamide. The presence of formamide resulted in a more destabilizing effect compared to the glycerol. This was shown by the smaller lamellar liquid crystal region obtained in the pseudoternary phase diagram containing equal weight ratio of water and formamide.     

Protein alkylation by acrylamide, its N-substituted derivatives and cross-linkers and its relevance to proteomics: a matrix assisted laser desorption/ionization-time of flight-mass spectrometry study.

The present review highlights some important alkylation pathways of proteins, as measured by matrix assisted laser desorption/ionization-time of flight (MALDI-TOF)-mass spectrometric analysis, engendered by acrylamide and a number of its derivatives, including N-substituted acrylamides, cross-linkers and Immobilines (the acrylamido weak acids and bases used to create immobilized pH gradients). The present data are of relevance in two-dimensional maps and proteome analysis. It is shown that acrylamide can alkylate the -SH group of proteins even when engaged in disulfide bridges. An order of reactivity is obtained for a series of cross-linkers, which are shown to have an extremely reacting double bond, with the second one almost unreactive, originating "pendant, unreacted ends", which can subtract proteins migrating in a gel by covalently affixing them to it. An analogous reactivity scale is constructed also for the Immobiline chemicals, whose reactivity is shown to be linearly dependent on the pK values, the least reacting species being the acidic compounds. When analyzing real-life samples by two-dimensional (2-D) maps, like milk powders, a number of modifications can be detected by MALDI-TOF mass spectra of eluted spots, including variable phosphorylation sites (up to nine) and lactosyl moieties. If, for eluting such spots, formic acid is used, MALDI-TOF mass spectrometry (MS) reveals an incredible number of formylation sites, on Ser and Thr residues.     

Ga2Br2R2 und Ga3I2R3 [R = C(SiMe3)3] — zwei neue elementorganische Galliumsubhalogenide mit einer bzw. zwei Ga‐Ga‐Bindungen

Ga₂Br₂R₂ and Ga₃I₂R₃ [R = C(SiMe₃)₃] — Two New Organoelement Subhalides of Gallium Containing One or Two Ga‐Ga Single Bonds The oxidation of the tetrahedral tetragallium cluster Ga₄[C(SiMe₃)₃]₄ ( 1 ) with elemental bromine in the presence of AlBr₃ yielded the corresponding gallium subhalide Ga₂Br₂R₂ [ 4 , R = C(SiMe₃)₃], which remains monomer even in the solid state and in which the Ga^II atoms are connected by a short Ga‐Ga single bond [243.2(2) pm]. The analogous diiodide Ga₂I₂R₂ ( 3 ), which was obtained on a similar route by our group only recently, did not react with lithium tert‐butanolate by substitution as originally expected. Instead, partial disproportionation occurred with the formation of the trigallium diiodide Ga₃I₂R₃ ( 6 ), in which three Ga atoms are connected by two Ga‐Ga single bonds (255.1 pm on average). Both terminal Ga atoms have a coordination number of four owing to the bridging function of both iodine atoms, while the inner one which has an oxidation number of +1 remains coordinatively unsaturated. An average oxidation state of 1.66 resulted for all atoms of the chain. The Ga^III compound {[GaI(R)(OCMe₃)(OH)]Li}₂ ( 7 ) was isolated as the second product of the disproportionation. It is a dimer in the solid state via Li‐O bridges and shows a hindered rotation of its tert‐butyl group.     

Raman scattering studies of sodalite for crystal structure and coloration mechanism

Summary Group-theoretical study of the vibrational modes of chlorosodalite [Na₄Al₃(SiO₄)₃]₂ has been carried out for theT _d ¹ space group. The Raman-active modes are evaluated and comparison is made with the experimental results on sodalite. It is shown that the experimental Raman spectrum does not support the structure of sodalite to beT _d ¹ but confirms it to beT _d ¹ . Raman scattering studies were performed on X-ray irradiated As-grown single crystal of chloro-sodalite to identify the coloration mechanism. Enhancement of oxygen twisting and stretching mode intensities on X-ray irradiation indicates the formation of neutral sodium colloidal aggregate during the coloration process. The authors of this paper have agreed to not receive the proofs for correction.     

New approach for evaluation of capillary column inverse gas chromatography

A mathematical model has been developed for the analysis of a capillary column IGC experiment. An important feature in the derivation of the model is the inclusion of Taylor dispersion effect. The model shows that Taylor dispersion effect has a very significant effect on elution profiles at low values of beta and gamma. Taylor dispersion effect causes more spread in the longitudinal direction and the peaks become broader. Taylor dispersion becomes more significant as beta becomes smaller. The model presented in this paper is more general than the usual IGC models and sets criteria equations to determine under what conditions the Taylor dispersion effect can be made negligible. A comparison between the present and usual IGC models above and near the glass temperature of the polymer is conducted. The analysis also describes the effect of kurtosis on pulse dispersion at extremely low diffusivities.     

Effect of experimental conditions on the analysis of sodium dodecyl sulphate polyacrylamide gel electrophoresis separated proteins by matrix-assisted laser desorption/ ionisation mass spectrometry

Two mixtures of proteins having molecular weights in the range approximately 8-97 kDa were separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and examined by delayed extraction matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS). Part of our aim in this study is to gain more insight into the influence of the various experimental conditions on the overall quality of the acquired mass spectral data. Different protein extraction procedures, two staining agents, and extraction times, were among the parameters assessed. In terms of the overall quality of the acquired mass spectra and the speed of protein recovery, ultrasonic assisted passive elution, into a solvent mixture containing formic acid/acetonitrile/2-isopropanol/water, was found to be more efficient than other elution procedures. The higher resolution associated with the delayed extraction mode allowed the identification of a number of protein modifications, including multiple formylation provoked by formic acid, cysteine alkylation caused by unpolymerised acrylamide monomers, and complexation with the staining reagents. The detection of these modifications, however, was limited to proteins under 30 kDa. Analysis of a ubiquitin tryptic digest by reflectron MALDI time-of-flight (TOF) allowed reliable identification of a number of the formylation sites.