Analysis of methylisothiazolones by ion pair high-performance liquid chromatography after pre-column derivatisation

Summary 2-Methyl-3(2H)-isothiazolone resp. 5-chloro-2-methyl-3(2H)-isothiazolone were isolated from a commercial methylisothiazolone formulation (Kathon CG) by flash chromatography and subsequently converted into the respective-thio-substituted acrylamide derivative with the help of the nucleophilic reagent hydrogensulfite. UV spectra and absorption characteristics, for both the derivates as well as the original methylisothiazolones are given and represented in comparison. The derivatives differ clearly in their absorption characteristics from the reactants. Especially in case of the non-chlorinated constituent, derivatisation leads to a distinct increase of its UV activity. For separation and quantification of the derivates an ion pair high-performance liquid Chromatographic method had been developed. With this method an independent system for verification of the content of methylisothiazolones, determined in conventional analysis, is available.

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Analytik von Methylisothiazolonen durch Ionenpaar-HPLC nach Vorsäulen-DerivatisierungTeil I. Derivatisierung von 2-Methyl-3(2H)-isothiazolon und 5-Chlor-2-methyl-3(2H)-isothiazolon

     

Complexes of Rare Earths and Dipicolinato Ions Encapsulated in X- and Y-zeolites: Luminescence Properties

The complexes {Ln(DP)}Z where Ln³⁺ = La³⁺ or Eu³⁺, DP is the dipicolinate ion (2,6)-pyridine dicarboxylate: C₅H₃N(COO^-)₂ and Z = one of the faujasite-type X or Y zeolites have been synthesized and investigated by XRD, Raman and IR spectroscopy, and Eu³⁺ luminescence spectroscopy. The rare earth complexes are synthesized inside the super-cages of the zeolites; the degree of complexation never exceeds1DP/1Ln. Only the Ln ions, which are in the super-cages, may be complexed. Luminescent europium complexes encapsulated in zeolite matrices were obtained. The ⁵D₀ F_J luminescence observed under excitation into the lowest-energy ligand-centered absorption band (275 nm)indicates that a DP to Eu energy transfer occurs in these systems. The complex versus the zeolite framework conformations influence the europium emission characteristics: the transfer is more efficient when the complexed europium [Eu(DP)]⁺ is directly bonded to the framework oxygen atoms rather than to a residual water molecule.     

A practical synthesis of 3-acyl cyclobutanones by [2 + 2] annulation. Mechanism and utility of the Zn(II)-catalyzed condensation of α-chloroenamines with electron-deficient alkenes

New conditions for the conversion of simple tertiary amides to α-chloroenamines and their use in Zn(II)-catalyzed cycloaddition reactions with commercial α,β-unsaturated carbonyl compounds allows rapid, regiocontrolled access to 3-acyl cyclobutanones. Reactions take place at ambient temperature without solvent, giving strained [2 + 2] adducts with all-carbon-substituted quaternary carbon atoms. Ab initio calculations of the putative keteniminium intermediate and studies with styrenyl olefins suggest a dual role for Zn(OTf)(2) during catalysis.     

Luminescent nano-composites generated from a spray

The spray-pyrolysis (SP) synthesis technique has been employed to obtain SiO₂:Eu³⁺ and γ-AlOOH:Eu³⁺. It was possible to obtain sub-micrometric spherical particles of SiO₂ with luminescent Eu³⁺ ions bonded to the silica surface or embedded in amorphous silica beads, by controlling the synthesis and annealing process. Boehmite γ-AlOOH doped with Eu³⁺ nanoparticles were synthesized by SP at moderate temperature (200 °C) with Eu³⁺ ions bonded to the surface hydroxyls of the boehmite nanocrystals. Luminescent nano-composites were obtained by controlled reaction of γ-AlOOH:Eu³⁺ nanocrystals with ASN (asparagine). In these nano-composites, the Eu³⁺ are held at the surface of the boehmite nanocrystals and partially shielded from interactions with additional luminescence quenchers (hydroxyl groups, water molecules).