Thermal Decomposition of Copper(I) Thiocarbamide Chloride Hemihydrate

Two combinations of simultaneous thermoanalytical techniques (TG+DTA and TG+EGA) were used to study the thermal decomposition of the title compound in order to gain a better insight into the spray pyrolytic processes leading to Cu2-xS and CuInS2 thin films. After dehydration a complex sequence of reactions starts above 220°C leading through several intermediates to the formation of CuO in air at 1000°C. In an inert atmosphere Cu2S is formed which in helium above 800°C partly decomposes to Cu. XRD and FTIR were used to identify the intermediate solid phases which in air included CuCl, Cu2OSO4, Cu2OCl2 and CuSO4. EGA-FTIR confirmed the complex reaction mechanism with NH3, HCl, H2O, COS, CO2 and some HCN as main gaseous products under oxidative conditions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Kinetics of the reactions of chlorinated methyl radicals (CH2Cl, CHCl2, and CCl3) with NO2 in the temperature range 220-360 K

The kinetics of the reactions of chlorinated methyl radicals (CH2Cl, CHCl2, and CCl3) with NO2 have been studied in direct measurements at temperatures between 220 and 360 K using a tubular flow reactor coupled to a photoionization mass spectrometer. The radicals have been homogeneously generated at 193 or 248 nm by pulsed laser photolysis of appropriate precursors. Decays of radical concentrations have been monitored in time-resolved measurements to obtain the reaction rate coefficients under pseudo-first-order conditions with the amount of NO2 being in large excess over radical concentrations. The bimolecular rate coefficients of all three reactions are independent of the bath gas (He or N2) and pressure within the experimental range (1-6 Torr) and are found to depend on temperature as follows: k(CH2Cl + NO2) = (2.16 +/- 0.08) x 10(-11) (T/300 K)(-1.12+/-0.24) cm3 molecule(-1) s(-1) (220-363 K), k(CHCl2 + NO2) = (8.90 +/- 0.16) x 10(-12) (T/300 K)(-1.48+/-0.13) cm3 molecule(-1) s(-1) (220-363 K), and k(CCl3 + NO2) = (3.35 +/- 0.10) x 10(-12) (T/300 K)(-2.2+/-0.4) cm3 molecule(-1) s(-1) (298-363 K), with the uncertainties given as one-standard deviations. Estimated overall uncertainties in the measured bimolecular reaction rate coefficients are about +/-25%. In the reactions CH2Cl + NO2, CHCl2 + NO2, and CCl3 + NO2, the products observed are formaldehyde, CHClO, and phosgene (CCl2O), respectively. In addition, a weak signal for the HCl formation has been detected for the CHCl2 + NO2 reaction.     

Estimation of uncertainty in electrochemical amperometric measurement of dissolved oxygen concentration

A procedure for the estimation of measurement uncertainty of dissolved oxygen (DO) concentration measurement based on the ISO approach is presented. It is based on a mathematical model that involves 14 input parameters. The uncertainty of DO concentration strongly depends on changes in experimental details (temperature difference between calibration and measurement, the time interval between calibration and measurement, etc.). The relative measurement uncertainty is, however, practically independent of the DO concentration itself. The uncertainty is the lowest if the calibration and the measurement are done at the same temperature and on the same day. A calculation tool is provided (in the form of a GUM Workbench file) for practitioners that can be used for uncertainty calculation of DO concentrations at very different experimental conditions.Electronic Supplementary Material The uncertainty calculation example is available as a GUM Workbench calculation file C_O2_meas.smu (GUM Workbench ver. 1.3.3, Metrodata GmbH) together with its data file Input_values.xls (MS Excel 97). For those users who do not have GUM Workbench, the full report of the GUM Workbench calculation is available as a PDF file C_O2_meas.pdf. This material is available via the Internet at .     

A versatile stereocontrolled approach to chiral tetrahydrofuran and tetrahydropyran derivatives by use of sequential asymmetric Horner-Wadsworth-Emmons and ring-closure reactions

An approach to chiral tetrahydrofuran and tetrahydropyran derivatives based on the sequential use of an asymmetric Horner-Wadsworth-Emmons reaction and a cyclization step is presented. The approach is both stereochemically and structurally versatile since three different cyclization methods can be employed starting from the same HWE product: (i) palladium-catalyzed substitution, (ii) hetero-Michael addition, or (iii) epoxide opening. The asymmetric HWE reaction controls the absolute configuration of the ultimate product, whereas the relative configuration is controlled by the combined influence of the geometric selectivity in the HWE reaction and the stereochemistry of the respective cyclization method.     

Studies on lanthanoid sulphites: V. thermal decomposition of cerium and neodymium sulphites

The preparation and thermal behaviour of Ce₂(SO₃)₃· 3H₂O, Nd₂(SO₃)₃·6H₂O and Nd₂(SO₃)₃ have been studied. Cerium sulphite undergoes first dehydration which is followed by decomposition to CeO₂ in the temperature range 500 – 850 °C. The decomposition involves two intermediate phases both in air and nitrogen. According to the TG curves the phases in air are Ce₂(SO₃)₂SO₄ and Ce₂SO₃(SO₄)₂. In nitrogen, Ce₂O₂SO₄ was identified and this provides a synthetic route to cerium oxysulphate.Neodymium sulphite decomposes to Nd₂O₂SO₄ when heated in air or in nitrogen up to 950°C. The intermediate levels observed do not correspond to single phases, and the reaction mechanism depends strongly on the experimental conditions.     

Quantum mechanical models correlating structure with selectivity: predicting the enantioselectivity of beta-amino alcohol catalysts in aldehyde alkylation

Quantitative structure selectivity relationship (QSSR) models are described that provide consistently reliable predictions for the asymmetric addition of Et2Zn to PhCHO catalyzed by beta-amino alcohols. Statistically valid two-variable linear regression models that correlate the structures of the chiral catalysts with their enantioselectivities are obtained from three-dimensional physical property grids. The strength of the present method is that statistical models obtained from a small set of experimentally determined selectivities and relatively simple theoretical calculations yield selectivity predictions that are as accurate as those derived from higher-level calculations of transition-structure energies. Only minutes of computing time are required. Simple models are obtained which permit straightforward physical interpretation and generate realistic predictions.     

In situ quadrupole mass spectrometry study of atomic-layer deposition of ZrO2 using Cp2Zr(CH3)2 and water

Reactions during the atomic layer deposition (ALD) process of ZrO(2) from Cp(2)Zr(CH(3))(2) and deuterated water as precursors were studied with a quadrupole mass spectrometer (QMS) at 210-440 degrees C. The detected reaction byproducts were CpD (m/z = 67) and CH(3)D (m/z = 17). Almost all (90%) of the CH(3) ligands were released during the Cp(2)Zr(CH(3))(2) precursor pulse because of exchange reactions with the OD-terminated surface, and the rest, during the D(2)O pulse. About 40% of the CpD was released during the metal precursor pulse, and 60%, during the D(2)O pulse. ALD-type self-limiting growth was confirmed from 210 to 400 degrees C. However, below 300 degrees C the growth rate was low. Precursor decomposition affected the film growth mechanism at temperatures exceeding 400 degrees C.     

A microfabricated micropillar liquid chromatographic chip monolithically integrated with an electrospray ionization tip

We present the first monolithically integrated silicon/glass liquid chromatography-electrospray ionization microchip for mass spectrometry. The microchip is fabricated by bonding a silicon wafer, which has deep reactive ion etched micropillar-filled channels, together with a glass lid. Both the silicon channel and the glass lid have a through-wafer etched sharp tip that produces a stable electrospray. The microchip is also compatible with laser induced fluorescence (LIF) detection, due to the glass lid. Separation of drugs in less than 5 minutes using either SiO(2) (normal phase) or C(18) coated (reversed-phase) pillars with good sensitivity was demonstrated with mass spectrometric detection as well as separation of fluorescent compounds with LIF detection.     

Atomic layer deposition of tungsten(III) oxide thin films from W2(NMe2)6 and water: precursor-based control of oxidation state in the thin film material

The atomic layer deposition of W2O3 films was demonstrated employing W2(NMe2)6 and water as precursors with substrate temperatures between 140 and 240 degrees C. At 180 degrees C, surface saturative growth was achieved with W2(NMe2)6 vapor pulse lengths of >/=2 s. The growth rate was about 1.4 A/cycle at substrate temperatures between 140 and 200 degrees C. Growth rates of 1.60 and 2.10 A/cycle were observed at 220 and 240 degrees C, respectively. In a series of films deposited at 180 degrees C, the film thicknesses varied linearly with the number of deposition cycles. Time-of-flight elastic recoil analyses demonstrated stoichiometric W2O3 films, with carbon, hydrogen, and nitrogen levels between 6.3 and 8.6, 11.9 and 14.2, and 4.6 and 5.0 at. %, respectively, at substrate temperatures of 160, 180, and 200 degrees C. The as-deposited films were amorphous. Atomic force microscopy showed root-mean-square surface roughnesses of 0.7 and 0.9 nm for films deposited at 180 and 200 degrees C, respectively. The resistivity of a film grown at 180 degrees C was 8500 microhm cm.