Composition and morphology of stack emissions from coal and oil fuelled boilers

Instrumental neutron activation analysis (INAA) together with scanning electron microscopy (SEM) have been used in the study of fly ash from large electric power and heating plants. Two basic kinds of fly ash originating either from brown coal or heavy-oil combustion can be characterized both by morphology and trace element composition. INAA technique used consisted of both short (1 min) and long (2 h) activations to ensure the determination of 30–40 elements in each fly ash sample. The average composition and determination limits obtained by INAA for coal fly ash produced in several electric power plants burning two kinds of brown coal have been compared with those obtained for fly ash originating from heating plants burning heavy-oil. Coal fly ash showed much higher concentrations of many elements especially of Sc. La, Th, Cs, Ce, Sm, Rb and Al in comparison with oil fly ash. On the other hand, the latter contained relatively high concentrations of V and Ni. The results of INAA of fly ash samples can be used for the projection of efficient separating devices and for the evaluation and prediction of contamination levels in the vicinity of large emission sources.     

Oxidative dearomatization of phenols and anilines via lambda(3)- and lambda(5)-iodane-mediated phenylation and oxygenation

Treatment of 2-methylphenols with chloro(diphenyl)-lambda(3)-iodane led to their regioselective dearomatizing 2-phenylation into cyclohexa-2,4-dienone derivatives via a proposed ligand coupling reaction. In the same vein of investigation, treatment of 2-methylanilines with the lambda(5)-iodane 2-iodoxybenzoic acid IBX reagent led to their regioselective dearomatization into previously undescribed ortho-quinol imines.     

Determination of enantiomeric excess and degree of hydrogenation in the enantioselective hydrogenation of ketopantolactone

Summary A new gas chromatographic method for the simultaneous determination of the degree of hydrogenation of ketopantolactone and the enantiomeric excess of pantolactone does not require any derivatisation.

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Bestimmung von Enantiomerenüberschuß und Hydriergrad bei der enantioselektiven Hydrierung von Ketopantolacton (Kurze Mitt.)

Zusammenfassung Zur Bestimmung des Hydriergrads von Ketopantolacton und des Enantiomerenüberschusses von Pantolacton wird ein neues gaschromatographisches Verfahren eingesetzt, das keine Derivatisierung erfordert.

     

Deprotonation-electrophile trapping of terminal epoxides

Organolithium-induced deprotonation of terminal epoxides in the presence of appropriate diamine ligands allows trapping with a range of electrophiles, yielding functionalised di- and tri-substituted epoxides in good yields and with control of stereochemistry at the epoxide.     

Radioanalytical quality control of11C,18F and123I-labelled compounds and radiopharmaceuticals

Radiochemical quality control using high performance high pressure liquid chromatography and, to some extent, gas chromatography is described for a variety of carrier-free¹¹C-,¹⁸F-and¹²³I-labelled compounds and radiopharmaceuticals. The particular problems associated with the handling of carrier-free compounds labelled with short-lived radionuclides are outlined, and chromatographic data are given for the separation and purification of such products.     

Laser-excited molecular flourescence spectrometry for the determination of traces of nonmetals : Part 1. determination of traces of fluoride,chloride and bromide based on diatomic molecules in a graphite furnace

For the determination of flouride, chloride and bromide, a suitable metal ion is added in a modified graphite tube atomizer. After drying and ashing, the substances are vaporized and diatomic molecules between the metal and nonmetal are formed. These molecules are excited by a pulsed dye laser and the resulting fluorescence is measured. At constant metal concentration, the fluorescence is proportional to the halide concentration. The diatomic molecules used are MgF, InCl and AlBr. The detection limits are 11 pg of fluoride, 15 pg of chloride and 70 pg of bromide in the 10-μl injections, corresponding to 6 x 10^?8 mol l^?1 fluoride, 4 x 10^?8 mol l^?1 chloride and 9 x 10^?8 mol l^?1 bromides.     

Janus-type isopropyl groups revealed by 1H-NMR spectra of alkylpyridines with lanthanide shift reagents (LSR)

Two Isomeric pyridines were designed and prepared : 2-isopropyl-4,5,6-trimethyl-(3) and 2-isopropyl-3,4,6-trimethyl-pyridine (7); the latter, with a buttressed isopropyl, leads to much lower induced shifts by Eu(dpm)₃ and Pr(dpm)₃ than the former, owing to the conformation in which the Janus-type iPr group how to the LSR a t-butyl-like face.     

Tetranuclear manganese(II) complexes of thiacalixarene macrocycles with trigonal prismatic six-coordinate geometries: synthesis, structure, and magnetic properties

Two tetranuclear manganese(II) complexes [Mn(II)4(thiaS)2] (1) and [Mn(II)4(thiaSO)2] (2) have been synthesized under solvothermal conditions in methanol with p-tert-butylthiacalix[4]arene (thiaS) and p-tert-butylsulfinylthiacalix[4]arene (thiaSO). For both complexes, the structure has been established from single-crystal X-ray diffraction. [Mn4(thiaS)2].H2O (1) crystallizes in the orthorhombic Immm (No. 71) space group with the following parameters: a = 18.213 (5) angstroms, b = 19.037 (5) angstroms, c = 29.159 (5) angstroms, V = 10110 (4) angstroms3, and Z = 4. [Mn4(thiaSO)2].H2O (2) crystallizes in the monoclinic C2/m (No. 12) space group with the following parameters: a = 33.046(1) angstroms, b = 19.5363 (8) angstroms, c = 15.7773 (9) angstroms, beta = 115.176 (2) degrees, V = 9218.3 (8) angstroms3, and Z = 4. The two complexes are neutral and are best described as manganese squares sandwiched between two thiacalixarene macrocycles. In both complexes, each manganese center is six-coordinated in a trigonal prismatic geometry with four phenoxo oxygen atoms plus two sulfur atoms for 1 or two oxygen atoms from SO groups for 2. The two tetranuclear complexes exhibit identical magnetic behaviors resulting from antiferromagnetic interactions between the four manganese centers. The simulation of the magnetic susceptibility was done considering a single exchange-coupling constant between the manganese(II) ions, J (H = -J(S1S2 + S2S3 + S3S4 + S1S4)). The best fits give the same result for the two complexes: g = 1.94 and J = -5.57 cm(-1).     

Isotherms for adsorption of cellobiohydrolase I and II fromtrichoderma reesei on microcrystalline cellulose

Adsorption to microcrystalline cellulose (Avicel) of pure cellobiohydrolase I and II (CBH I and CBH II) fromTrichoderma reesei has been studied. Adsorption isotherms of the enzymes were measured at 4‡C using CBH I and CBH II alone and in reconstituted equimolar mixtures. Several models (Langmuir, Freundlich, Temkin, Jovanovic) were tested to describe the experimental adsorption isotherms. The isotherms did not follow the basic (one site) Langmuir equation that has often been used to describe adsorption isotherms of cellulases; correlation coefficients (R²) were only 0.926 and 0.947, for CBH I and II, respectively. The experimental isotherms were best described by a model of Langmuir type with two adsorption sites and by a combined Langmuir-Freundlich model (analogous to the Hill equation); using these models the correlation coefficients were in most cases higher than 0.995. Apparent binding parameters derived from the two sites Langmuir model indicated stronger binding of CBH II compared to CBH I; the distribution coefficients were 20.7 and 3.7 L/g for the two enzymes, respectively. The binding capacity, on the other hand, was higher for CBH I, 1.0 Μmol (67 mg) per gram Avicel, compared to 0.57 Μmol/g (30 mg/g) for CBH II. The isotherms when analyzed with the combined Langmuir-Freundlich model indicated presence of unequal binding sites on cellulose and/or negative cooperativity in the binding of the enzyme molecules.     

Vapor Pressure and Solid Phases of Methanol below Its Triple Point Temperature

We present an experimental work devoted to study of the thermodynamical properties of solid methanol. We combine Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS) to measure, for the first time, the vapor pressure of various methanol solid phases and determine their Clausius-Clapeyron equations. We perform our experiments between T = 130 K and the triple point temperature T(t) = 175.61 K. When methanol is condensed from its vapor below T(t), we observe three different solid phases depending on temperature. A condensation at T = 130 K forms a metastable phase with an enthalpy of sublimation deltaH(metastable-vapor) = 42.9 +/- 0.5 kJ.mol(-1). Upon heating, this phase transforms itself at T approximately 145 K to the alpha-phase that has an enthalpy of sublimation deltaH(alpha-vapor) = 46.9 +/- 0.2 kJ.mol(-1). Cooling the alpha-phase does not lead back to the metastable phase, whereas heating this alpha-phase leads to the beta-phase occurrence at T(alpha-beta) = 157.36 K. This latter one is stable until T(t) and has an enthalpy of sublimation deltaH(beta-vapor) = 44.2 +/- 0.5 kJ.mol(-1).