Classical chemical sciences
Oxidation of thirty six monosubstituted benzaldehydes by quinolinium fluorochromate (QFC) in dimethylsulphoxide (DMSO), leads to the formation of corresponding benzoic acids. The reaction is of first order with respect to QFC. A Michaelis-Menten type kinetics was observed with respect to the reactants. The reaction is promoted by hydrogen ions; the hydrogen‑ion dependence has the form kobs=a +b[H+]. The oxidation of [2H]benzaldehyde (PhCDO) exhibited a substantial primary kinetic isotope effect. The reaction was studied in nineteen different organic solvents and the effect of solvent was analysed using Taft's and Swain's multi-parametric equations. The rates of the oxidation of para‑ and meta‑substituted benzaldehydes showed excellent correlation in terms of Charton’s triparametric LDR equation, whereas the oxidation of ortho-substituted benzaldehydes were correlated well with tetraperametric LDRS equation. The oxidation of para-substituted benzaldehydes is more susceptible to the delocalized effect than is the oxidation of ortho- and meta- substituted compounds, which display a greater dependence on the field effect. The positive value of h suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subjected to steric acceleration by the ortho-substituents. A suitable mechanism has been proposed.
The newest results in the chromatographic analysis of pesticides present in foods and food products are collected and the results are critically evaluated. Examples for the employment of preconcentration and prepurification technologies, gas chromatography using ECD, NPD, MS and MS/MS detection methods, liquid chromatographic methodologies such as thin-layer chromatography, high performance liquid chromatographic methods as well as electrically driven systems are presented. The advantages and disadvantages of the various chromatographic technologies are shortly discussed and the efficacies of the methodologies are compared. Pesticides included in the review are insecticides, herbicides, acaricides, organophosphorous and organochlorine compounds The application of the chromatographic methods for the determination of pesticides in a wide variety foods and food products is discussed in detail.
The newest results in the application of cluster analysis a multivariate mathematical-statistical technique for the evaluation of large retention data matrices are collected. The results are critically evaluated, and examples for the application in gas chromatography, liquid chromatographic techniques such as thin-layer chromatography and high-performance liquid chromatography, as well as in electrically driven systems are presented.
The oxidation of nine aliphatic primary alcohols by tetrakis (pyridine) silver dichromate (TPSD) in dimethylsulfoxide leads to the formation of corresponding aldehydes. The reaction is first order with respect to TPSD. A Michaelis-Menten type kinetics is observed with respect to alcohols. The reaction is promoted by hydrogen ions; the hydrogen‑ion dependence has the form kobs= a + b [H+]. The oxidation of [1,1‑2H2]ethanol (MeCD2OH) exhibits a substantial primary kinetic isotope effect (kH/kD = 5.85 at 298K). The reaction has been studied in nineteen different organic solvents. The solvent effect was analysed using Taft's and Swain's multiparametric equations. The rate of oxidation is susceptible to both polar and steric effects of the substituents. A suitable mechanism has been proposed.
The newest results in the chromatographic analysis of xenobiotics present in biological and environmntal matrices are compiled and the results are critically evaluated. Examples for the employment of preconcentration and prepurification technologies, gas chromatography using electron capture detection (ECD), nitrogen phosphor detector (NPD), various mass spectrometric detection methods (MS, MS/MS, etc), liquid chromatographic methodologies such as thin-layer chromatography (TLC), high performance liquid chromatographic methods (HPLC) as well as electrically driven systems are presented. The advantages and disasdvantages of the various chromatographic technologies are shortly discussed and the efficacies of the methodologies are compared. Xenobiotics included in the review are volatile organic compounds (VOC), hydrocarbons and hydrocarbon-based pollutants, polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenols (PCB), other polyhalogenated compounds, pesticides, etc. The application of various chromatographic methods for the determination of xenobiotics in a wide variety of biological and environmental matrices is discussed in detail.
3-Chloro-4-fluoro-1,2,5-thiadiazole has been synthesized and investigated in the gas phase by IR spectroscopy and UV photoelectron spectroscopy. The ground-state geometry of the neutral molecule has been obtained from quantum-chemical calculations using the B3LYP/aug-cc-pV(T+d)Z method. Ionization potentials have been determined and the electronic structure has been discussed within the frame of molecular orbital theory. IR and photoelectron spectroscopies, supported by quantum-chemical calculations at the B3LYP and SAC-CI/aug-cc-pV(T+d)Z levels, provide a detailed investigation into the vibrational and electronic character of the molecule.
Materials and environmental chemistry
A solid by-product formed as deposit in the pyrolysis process of poly(acrylonitrile-co-methyl methacrylate) was analyzed and two main components, namely ammonium sulphate and 1,3,5-tricyanobenzene were identified by IR, GC-IR, TG-MS and XRD methods. The main organic components, 1,3,5-tricyanobenzene was crystallized out from acetone extract as colourless needles. 1,3,5-Tricyanobenzene proved to be mutagenic by bacterial (Salmonella typhimurium TA98 and TA1537) reverse mutation assay.
Random mixtures of waste plastics raw materials were thermolysed into liquid hydrocarbons at laboratory scales in a batch process by using a stainless steel reactor. Two series of experiments were carried out with random mixtures of waste plastics such as low and high density polyethylene, polypropylene, and polystyrene in the presence of 10 and 20 % calcium carbonate, respectively, at temperatures between 100 and 430 ºC. Four types of randomly mixed waste plastics were used in each series of experiments. The hydrocarbon oils formed were analyzed by using a gas chromatography and mass spectrometer (GC/MS) to determine the amounts and types of hydrocarbons. By using 10% calcium carbonate, the formed hydrocarbon mixture contained C4 to C40 compounds while, in the presence of 20% calcium carbonate, the product consists of C3 to C27 hydrocarbons determined by GC/MS analysis. Due to the high number of hydrocarbons in the oils formed in each series of thermal decomposition experiment, the oily products can be used as fuels for internal combustion engines or electric power plants.
Industrial and engineering chemistry
By using Yanhua FCC gasoline and a fraction of Yanhua FCC gasoline (boiling point < 90 °C) as a feedstock, the effects of reaction temperature, Weight Hour Space Velocity (WHSV), and feedstock performance on yields of LPG, aromatics and propylene production were studied in a confined fluidized bed reactor. The experimental results show that yields of aromatics, propylene, and aromatics + propylene for both Yanhua FCC gasoline and the selected fraction of Yanhua FCC gasoline increase with the increase of reaction temperature at the same WHSV. Yields of aromatics, propylene and aromatics+propylene decrease with the increase of WHSV at the same reaction temperature.
By using Yanhua FCC gasoline and a selected fraction of Yanhua FCC gasoline as feedstocks, the effects of reaction temperature, Weight Hour Space Velocity (WHSV), and feedstock performance on yields of LPG, aromatics, and propylene production were investigated in a confined fluidized bed reactor. The experimental result show that yields of aromatics, propylene, and aromatics + propylene for both Yanhua FCC gasoline and fraction of Yanhua FCC gasoline increase with the increase of reaction temperature at the same WHSV. Yields of aromatics, propylene, and aromatics + propylene decrease with the increase of WHSV at the same reaction temperature. Eight-lump kinetics and ten-lump kinetics are pointed out. The experimental results show that both kinetic models can predict the distribution of gasoline conversion and the composition of hydrocarbons of gasoline products under the different reaction conditions.
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