Zur reaktion von metall-koordiniertem kohlenmonoxid mit yliden: XXI. Ambidentes verhalten von eisenacyl-phosphor-yliden gegenüber methylfluorsulfonsäureester: Umwandlung in eisenacyl-phosphoniumsalze oder β-phosphoniovinyl- eisenkomplexe

]The reaction of the acyliron phosphorus ylide Cp(CO)₂FeC(O)CHPMe₃ with MeOSO₂F yields the acyliron phosphonium salt [Cp(CO)₂FeC(O)C(Me)- HPMe₃]SO₃F, while Cp(CO)₂FeC(O)C(Me)PEt₃ undergoes exclusively O-alkylation to the complex salt [Cp(CO)₂FeC(OMe)C(Me)PEt₃]SO₃F, (A). The acyliron ylides Cp(CO)₂FeC(O)C(R)PR₃ (R  R′  Me; or R  H, R′  Et) are converted to a mixture of the O- and C-methylated products. According to spectroscopic data and X-ray diffraction analysis of A the O- alkylation products have to be described as phosphoniovinyliron complexes.     

Rate constants of the thermal cis‐trans isomerization of azobenzene dyes in solvents,acetone/water mixtures,and in microheterogeneous surfactant solutions

Rate constants k_iso of the thermal cis‐trans isomerization of four 4,4’‐nitro‐aminoazobenzenes with different amino groups have been determined in homogeneous aprotic solvents and polyglykol oligomers, primarily by means of conventional flash photolysis. The rate constants have been correlated with polarity (according to λ_max from UV/Vis absorption spectra of the trans isomers) and bulk viscosity of the solvents. Qualitative conclusions about the influence of varying concentrations of water with respect to polarity and hydrogen bonding on k_iso‐ and λ_max‐values in acetone/water mixtures were derived. Based on these results the data from microheterogeneous solutions have been interpreted. In microheterogeneous water/surfactant solutions k_iso‐values of selected azo dyes were strongly dependent on the concentrations of SDS, Triton^®X‐100, C₁₂EO₈ in water, and varied with the composition of bicontinuous microemulsions of Igepal^® CA‐520/ heptane/water. The large spread of isomerization rate constants is in part due to varying microviscosity. Replacement of H₂O by D₂O in aqueous surfactant solutions produced surprisingly large kinetic solvent isotope effects. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 337–350, 1999     

Chemical and Biological Characteristics of Oxytropis pseudoglandulosa Plant of Mongolian Origin

Oxytropis pseudoglandulosa is used in Mongolian traditional medicine due to its numerous reported health-promoting effects. To date, there are very few scientific reports that describe this species. In this article, its volatile oil composition, lipid extract composition, total phenolic and flavonoid content, antibacterial and allergenic properties are elucidated for the first time. Hexadecanoic acid, fokienol and tricosane were determined as the most notable components of the volatile oil, at 13.13, 11.46 and 5.55%, respectively. Methyl benzoate was shown to be the most abundant component of lipid extract at 40.69, followed by (E)-prop-2-enoic acid, 3-phenyl- and benzenepropanoic acid, at 18.55 and 9.97%. With a TPC of 6.620 mg GAE g⁻¹ and TFC of 10.316 mg QE g⁻¹, the plant extract of O. pseudoglandulosa indicated good antioxidant activity measured by IC₅₀ at 18.761 µg mL⁻¹. Of the 12 tested microorganisms, B. subtilis and S. cerevisiae were the shown to be most susceptible to the plant extract, with MIC at 2.081 and 0.260% (v/v), respectively. Bet v 1—a major birch pollen allergen found in plant-based foods—was determined to be at 192.02 ng g⁻¹ with ELISA. Such a wide spectrum of biological activity indicated by O. pseudoglandulosa lends credence for its application in food industry. Its exerted antioxidant and antimicrobial effects could improve preservation of low-processed food dedicated for consumers afflicted with allergies. Hexadecanoic acid supplemented in foods with dietary plant extracts could add to the potential anti-inflammatory impact. The analysis of lipid makeup suggests O. pseudoglandulosa extract could also be considered as natural pesticide in organic farming.     

Synthesis of Epoxy Methacrylate Resin and Coatings Preparation by Cationic and Radical Photocrosslinking

This work involves the synthesis of hybrid oligomers based on the epoxy methacrylate resin. The EA resin was obtained by the modification of industrial-grade bisphenol A-based epoxy resin and methacrylic acid has been synthesized in order to develop multifunctional resins comprising both epoxide group and reactive, terminal unsaturation. Owing to the presence of both epoxy and double carbon–carbon pendant groups, the reaction product exhibits photocrosslinking via two distinct mechanisms: (i) cationic ring-opening polymerization and (ii) free radical polymerization. Monitoring of EA synthesis reactions over time using PAVs, MAAC and NV parameters, and the FT-IR method reveals that esterification reactions proceed faster at the start, exhibiting over 40% of conversion within the initial 60 min, which can be associated with a relatively high concentration of reactive sites and low viscosity of the reaction mixture at the initial reaction stage. With the further increase in the reaction time, the reaction rate tends to decrease. The control of the EA synthesis process can guide how to adjust reactions to obtain EAs with desired characteristics. Based on obtained values, one can state that the optimum synthesis time of about 4–5 h should be adopted to prepare EAs having both epoxy groups and unsaturated double bonds. The structure of the obtained EA was confirmed by FT-IR and NMR methods, as well as the determination of partial acid value and epoxy equivalent. Samples at various stages of synthesis were cured with UV radiation in order to study the kinetics of the process according to cationic and radical polymerization determined via photo-differential scanning calorimetry (photo-DSC) and real-time infrared spectroscopy (RT-IR) and then the properties of the cured coatings were tested. It turned out that the cationic polymerization was slower with a lower conversion of the photoreactive groups, as compared to the radical polymerization. All the obtained EA coatings were characterized by good properties of cured coatings and can be successfully used in the coating-forming sector.     

How Does Nature Cleave Sulfuric Acid Esters? A Novel Posttranslational Modification of Sulfatases

A rare inherited disease , multiple sulfatase deficiency, is attributed to a defect in a posttranslational protein modification which is essential for the catalytic activity of all known sulfatases. Structure analysis of arylsulfatase A, the enzyme that cleaves sulfatide 1 , shows that the modification of a cysteine residue into a formylglycine residue is essential for catalytic activity.     

Solvent Trapping during Large Volume Injection with an Early Vapor Exit. Part 3: The Main Cause of Volatile Component Loss during Partially Concurrent Evaporation

When 0.53 mm i.d. uncoated precolumns connected to a solvent vapor exit are used for sample introduction with partially concurrent solvent evaporation, substantial losses of volatile solutes are often observed. They were found to be the consequence of solute accumulation at the front end of the flooded zone, which in turn is the result of a strong pressure drop over the flooded zone owing to the formation of plugs of sample liquid. The pressure drop causes significant solvent evaporation at the front, which enriches the solute material there and causes its loss. The use of 0.32 mm i.d. restrictions between the uncoated precolumn and the vapor exit greatly reduced this problem.     

On-line solvent evaporator for coupled LC systems: Further developments

An on-line solvent (eluent) evaporator is used for reconcentrating a fraction from a first LC column before introduction into a second LC separation step, possibly involving another mobile phase. For pentane and pentane containing 10 % of dichloromethane, evaporation rates of 1 ml/min were achieved. On evaporating a volume of 6 ml, 2-ethylnaphthalene was retained to more than 75%. Separation of aliphatic and polyaromatic hydrocarbons in a linseed oil is shown as an application.