Ein Synergetischer Effekt bei Chlorierungen von Silicagel bzw. Metakaolin mit gasförmigen,Aluminiumchlorid enthaltenden Chlorierungsmitteln

A Synergetic Effect in Chlorination of Silicagel and Metakaolin with Aluminium Chloride Containing Chlorinating Agents The reactivity of silicagel with CCl₄, C₂Cl₆, C₂Cl₄, COCl₂, S₂Cl₂/Cl₂, and Cl₂/carbon is low up to 1000 K. Aluminium chloride under these conditions is a little more reactive above 600 K. But gaseous mixtures of aluminium chloride with CCl₄, C₂Cl₆, and S₂Cl₂/Cl₂ resp., show a synergetic effect: They attain conversion grades much higher than the sum of those obtained with each of the single components. The reactivity of aluminium chloride/CCl₄ mixtures with silicagel in dependence on temperature and partial pressure has been followed. Metakaolin is reacted by such a mixture synergetically and with increased silicate conversion. Practical consequences of this effect are demonstrated and essential phenomena involved in metakaolin chlorination are explained. A mechanistic model of the synergetic effect has been developed.     

Collision-induced dissociations of substituted benzyl anions: Deprotonated 2-Phenyl-1,3-dithiane

Deprotonated 2-phenyl-1,3-dithiane undergoes competitive losses of H˙, C₃H₆ C₂H₄S, C₃H₄S, C₇H₆S, C₁₀H₁₀ and C₁₀H₁₀S upon collisional activation. The elimination of H occurs from the phenyl ring. The loss of C₃H₆ occurs by simple cleavage of the dithiane ring. All other processes involve specific proton transfer followed by either cleavage or internal nucleophilic displacement.     

Determination of chlorprothixene and its sulfoxide metabolite in plasma by high-performance liquid chromatography with ultraviolet and amperometric detection

This communication describes a rapid, sensitive and selective method for the assay of chlorprothixene and its sulfoxide metabolite in human plasma, using reversed-phase high-performance liquid chromatography. Alkalinized plasma was extracted with heptane--isoamyl alcohol (99:1), after addition of thioridazine as the internal standard. The residue obtained after evaporation of this extract was chromatographed on a cyano column, using acetonitrile--0.02 M potassium dihydrogen phosphate pH 4.5 (60:40) as the mobile phase with ultraviolet (229 nm) detection. Quantitation was based on peak height ratios over the concentration range of 5.0-50.0 ng/ml for both compounds with 85% and 90% recovery for chlorprothixene and its sulfoxide metabolite, respectively, using a 1.0-ml plasma sample. The assay chromatographically resolves chlorprothixene and the sulfoxide metabolite from the N-desmethyl metabolite, which can only be semi-quantitated owing to low and variable recoveries. The method was used to obtain plasma concentration versus time profiles in two subjects after oral administration of 100 mg of chlorprothixene suspension and in two additional subjects following overdosages of chlorprothixene estimated to exceed several hundred milligrams. These analyses demonstrated that the sulfoxide metabolite is the predominant plasma component following therapeutic administration and overdosages. High-performance liquid chromatography with oxidative amperometric detection with the glassy carbon electrode was also evaluated. Although this procedure demonstrated comparable sensitivity and precision to ultraviolet detection for the analysis of chlorprothixene and N-desmethyl chlorprothixene, the sulfoxide metabolite could not be measured with high sensitivity (less than 100 ng/ml) owing to endogenous interferences. Hence the utility of this alternative assay technique is limited.     

Kuhn and the Chemical Revolution: a re-assessment

A recent paper by Hoyningen-Huene argues that the Chemical Revolution is an excellent example of the success of Kuhn’s theory. This paper gives a succinct account of some counter-arguments and briefly refers to some further existing counter-arguments. While Kuhn’s theory does have a small number of more or less successful elements, it has been widely recognised that in general Kuhn’s theory is a “preformed and relatively inflexible framework” (1962, p. 24) which does not fit particular historical examples well; this paper clarifies that those examples include the Chemical Revolution.     

Properties of zirconium compounds likely to be of interest to the analytical chemist

A review of zirconium chemistry, with emphasis on the features underlying the chemical methods of determining this element, and an application of zirconium compounds in the analytical chemistry of other species.