DTA and X-ray diffraction investigations of laser-irradiated CeO2 powders

The TG and DTA curves and diffractograms of powdered CeO₂ samples irradiated with a CO₂ laser beam with powers of 0.41–1.39 kW/cm² are presented. The laser treatment induced structural changes and probably generation of a metastable phase. X-ray diffraction coupled with thermal analysis was used to establish the structural modifications in the irradiated samples after heating.     

On the evaluation of the nonisothermal kinetic parameters of (GeS2)0.3(Sb2S3)0.7 crystallization using the IKP method

The isoconversional method suggested by Friedman and the invariant kinetic parameters method (IKP) were used in order to examine the kinetics of the nonisothermal crystallization of (GeS₂)_0.3(Sb₂S₃)_0.7. The objective of the paper is to show the usefulness of the IKP method both for determining the activation parameters as well as the model of the investigated process. It was shown that the kinetic triplet [(E, A, f(α), where E is the activation energy, A is the preexponential factor, and f(α) is the differential function of conversion], which results through the application of the IKP method, depends on the set of kinetic models considered. For different sets of kinetic models, proportional values of f(α) are obtained. A criterion for the selection of this set, the use of which lead to the true kinetic triplet corresponding to the analyzed process (E = 163.2 kJ mol^?1; A = 2.47 × 10¹² min^?1 and the Avrami‐Erofeev model, A_m, for m = 2.5–2.6 was suggested. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 309–315, 2004     

N-labelling studies of the reaction of 2,6-di-t-butyl-4-methyl-4-nitrocyclohexa-2,5-dienone with nitrogen dioxide; A revised mechanism

Reaction of the ¹⁵N-4-nitrodienone (1) with excess nitrogen dioxide in benzene for 16 h gives the 4,5,6-trinitro ketone (2), labelled (¹⁵NO₂) at C6 but not at C4, and recovered 4-nitrodienone (1) in which extensive loss of ¹⁵NO₂ has occurred. The mechanistic implications of these and related results are discussed.     

A variational formulation of the rate equations for closed chemical systems

This paper presents a variational formulation of the kinetic equations corresponding to a closed chemical system.

---

, .

     

Multiple nitrene insertions into metal-sulfur bonds of dithiocarbamate complexes: synthesis of sulfido-amido and zwitterionic tetraamido complexes

The iodine(III) reagent, PhI[double bond, length as m-dash]NTs, acts as a source of the nitrene fragment NTs, which undergoes facile insertion into the metal-sulfur bonds of a range of dithiocarbamate complexes. Addition of two equivalents of PhI=NTs to [M(S(2)CNR2)2] affords sulfido-amido complexes [M{SC(NR2)SNTs}2](M=Ni, Cu), which insert two further nitrene fragments to afford zwitterionic tetraamido complexes [M{TsNSC(NR2)SNTs}2](M=Co, Ni, Cu). Crystallographic studies have been carried out on both types of complex allowing possible resonance hydrids of the new ligand types to be assessed.