Volume 232, Issue 2

Double-imaging photoelectron/photoion coincidence (i 2 PEPICO) spectroscopy using a multiplexing, time-efficient, fixed-photon-energy approach offers important opportunities of gas-phase analysis. Building on successful applications in combustion systems that have demonstrated the discriminative power of this technique, we attempt here to push the limits of its application further to more chemically complex combustion examples. The present investigation is devoted to identifying and potentially quantifying compounds featuring five heavy atoms in laminar, premixed low-pressure flames of hydrocarbon and oxygenated fuels and their mixtures. In these combustion examples from flames of cyclopentene, iso -pentane, iso -pentane blended with dimethyl ether (DME), and diethyl ether (DEE), we focus on the unambiguous assignment and quantitative detection of species with the sum formulae C 5 H 6 , C 5 H 7 , C 5 H 8 , C 5 H 10 , and C 4 H 8 O in the respective isomer mixtures, attempting to provide answers to specific chemical questions for each of these examples. To analyze the obtained i 2 PEPICO results from these combustion situations, photoelectron spectra (PES) from pure reference compounds, including several examples previously unavailable in the literature, were recorded with the same experimental setup as used in the flame measurements. In addition, PES of two species where reference spectra have not been obtained, namely 2-methyl-1-butene (C 5 H 10 ) and the 2-cyclopentenyl radical (C 5 H 7 ), were calculated on the basis of high-level ab initio calculations and Franck-Condon (FC) simulations. These reference measurements and quantum chemical calculations support the early fuel decomposition scheme in the cyclopentene flame towards 2-cyclopentenyl as the dominant fuel radical as well as the prevalence of branched intermediates in the early fuel destruction reactions in the iso -pentane flame, with only minor influences from DME addition. Furthermore, the presence of ethyl vinyl ether (EVE) in DEE flames that was predicted by a recent DEE combustion mechanism could be confirmed unambiguously. While combustion measurements using i 2 PEPICO can be readily obtained in isomer-rich situations, we wish to highlight the crucial need for high-quality reference information to assign and evaluate the obtained spectra.

Lignin is the second most abundant natural polymer and a promissing feedstock for the generation of renewable aromatic chemicals. We present an fundamental approach for the electrocatalytic cleavage of lignin dissolved in a recoverable, inexpensive ionic liquid using mixed metal oxide electrodes of different compositions. The distribution of depolymerization products generated by electrochemical oxidation were analyzed by means of mass spectrometry. The distribution and yield of the cracked species was found to depended strongly on the implemented metal catalyst and therefore offers the potential to tailor the amount and composition of the low molecular weight cleavage products. This approach could help to provide a more sustainable valorization of lignin for the potential production of high value aromatic compounds due to synergistic effects.

In search for a probable local solution for Qarasu River problems and based on our prescience about metal ion chelating/reducing ability of tannins which are found in large amount in oak acorns bark, Quercus brantii (Persian oak) acorns bark extract was exploited as reducing/capping agent in silver nanoparticles synthesis. Synthesis was carried out as a single-step method at room temperature, and without consuming any external energy by using these renewable barks. The crystallinity, size and shape of the nanoparticles were characterized by X-ray diffraction and scanning electron microscopy (SEM) respectively. The involvement of phenolic compounds in metal ion reduction was supported by UV-Visible and infrared spectroscopies and by acidity and conductivity measurements. The SEM-based particle size distribution analysis and antimicrobial susceptibility test of oak acorns bark-extract-mediated silver nanoparticles against bacterial effluent were pointed out to the critical proportion of silver salt to the capping/reducing agent. It seems that the bactericidal action depends on the extent to which accumulation of silver nanoparticle (Ag-Np) in bacterial cell surface alters the silver nanoparticle colloidal stability in broth medium.

The kinetics and mechanism of manganese(II) catalyzed oxidation of atenolol by cerium(IV) sulfate in aqueous H 2 SO 4 at a constant ionic strength of 0.50 mol dm -3 was studied spectrophotometrically. The reaction showed first order kinetics in cerium(IV) whereas fractional order in both manganese(II) and atenolol. Addition of products showed no effect on the rate of the reaction. The main product, 2-(4-(2-hydroxy-3-oxopropoxy)phenyl)acetamide, was identified with the aid of IR and mass spectral data. Stoichiometry with respect to the drug substrate and reagent was established as 2:1. Added H 2 SO 4 , SO 4 2− and HSO 4 − showed negligible effect on the rate of the reaction. HCe(SO 4 ) 3 − was found to be the predominant reactive species under the specified experimental conditions. The rate constants ( k ), catalytic constant ( k c ) and equilibrium constant ( K 6 ) for the proposed mechanism were determined. The kinetic and thermodynamic activation parameters were computed for both the slow rate determining step and complex forming equilibrium step.

The present paper shows a comparative study on the synthesis of nanostructured tin oxide in the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethylsulfonate ([EMIm]TfO) by sol–gel and sonochemical methods. The XRD results of the synthesized materials revealed the formation of single tetragonal phase of SnO 2 by sol–gel method whereas a mixture of tetragonal SnO and orthorhombic SnO 2 phases was obtained by the sonochemical method. The sonochemical approach led to the formation of finer nanoparticales with a higher specific surface area than that of the sol–gel synthesized oxide. The average sizes of tin oxide nanoparticles were found to be about 30 nm and 15 nm for the particles obtained by sol–gel and sonochemical methods, respectively. The surface area of SnO 2 nanopowder obtained by the sol–gel method (calcined at 500 °C) was estimated to be 11.6 m 2 g −1 , and the mean pore diameter was found to be 6.33 nm. Whereas the mixed SnO/SnO 2 sample (calcined at 500 °C) obtained by the sonochemical method exhibited a higher surface area of 43.11 m 2 g −1 and an average pore diameter of 1.90 nm. The band gap of the synthesized tin oxides was estimated from the UV-vis. results to be 4.01 and 4.25 eV for the sol–gel and sonochemically synthesized samples, respectively.

The solubilization and solvatochromic behavior of piroxicam (PRX) were analyzed using UV-vis spectroscopy in neat (protic and aprotic) and binary solvent mixtures. The effects of solvent dipolarity/polarizability and solvent–solute hydrogen bonding interactions on the absorption maxima were evaluated by means of the linear solvation energy relationship concept of Kamlet and Taft. This analysis indicated that both interactions play an important role in the position of the absorption maxima in neat solvents. While, the PRX solubility depends on the solute–solvent specific interactions, polarizability and the cohesive forces of the solvent, manifested mainly by means of the Hildebrand’s solubility parameter. Preferential solvation (PS) was studied in 10 binary mixtures. A non-ideal behavior of the wavenumber curve as the function of analytical mole fraction of co-solvent was detected. Index of preferential solvation, as well as the influence of solvent parameters were calculated. The process of dissolution was analyzed in aqueous binary mixtures of ethanol, ethylene glycol and propylene glycol. They were not spontaneous in all proportions, but when water concentration decreases in the mixtures, the process becomes more spontaneous.

Assembly of pyridine-2-aldoxime drug with cucurbit [6]uril (CB[6]) has been investigated by 1 H-NMR and 2D-ROESY NMR, UV-Vis spectroscopy, FT-IR spectroscopy, surface tension and conductivity measurements in aqueous saline environment. The distinct cationic receptor feature and the cavity dimension of the CB[6] emphasize that the macro-cyclic host molecule remain as complex with the nerve stimulus drug molecule. The results obtained from surface tension and specific conductivity measurements suggest 1:1 inclusion complex formation between drug and CB[6]. The stability constant evaluated by UV-Vis spectroscopic approach is 2.21×10 5 M −1 at 298.15 K, which indicates that the complex is sufficiently stable at physiological temperature.

Magnetic treatment of aqueous solutions containing dissolved CaCO 3 is known to affect its precipitation exerted by heating or raising the pH of the solution. In this work, experiments have been performed on two kinds of water: (a) a simulated water containing only CaCO 3 as dissolved salt and (b) a real brackish water sample of high total hardness from an industrial area containing a wide range of impurity salts. It has been discovered for the first time that using a sinusoidal magnetic field, treatment at a frequency of ca. 150 kHz (for a range of 0–1000 kHz) results in the maximum calcite precipitation independent of the initial water composition. The discovered phenomenon could be explained based on the resonance taking place due to the synchronization of the induced magnetic field with the proton exchange rate of water molecules.