A study for the selection of NPE-free cocktails for LSC routine measurements

Journal of Radioanalytical and Nuclear Chemistry - In this paper a study for the selection of an NPE (nonylphenol ethoxylates)—free cocktail is discussed in order to be used for our routine...     

Multiple nontrivial solutions for nonlinear periodic problems with the p-Laplacian

We consider a nonlinear periodic problem driven by the scalar p-Laplacian with a nonsmooth potential (hemivariational inequality). Using the degree theory for multivalued perturbations of (S)₊-operators and the spectrum of a class of weighted eigenvalue problems for the scalar p-Laplacian, we prove the existence of at least three distinct nontrivial solutions, two of which have constant sign.     

Unsaturated end-groups in PVC—IV

NMR spectra are reported for the following compounds: 1-chloropentene-2, 1,1-dichloropentene-2 and 1,2-dichloropentene-2. They represent models for unsaturated end-groups in PVC and are the result of allylic rearrangement of the compounds: 3-chloropentene-1, 1,3-dichloropentene-1 and 2,3-dichloropentene-1. Their NMR characteristics were determined to make possible the identification of these structural defects in PVC.     

Metallocene monomers and polymers. Ferrocenyl and ferrocenylene derivatives

The synthesis and study of some polyenes, polýiminoimides and Schiff polybases with ferrocene obtained by either polymerization or polycondensation are reported.The following monomers were used: ethynylferrocene, 1-chloro-1′-ethynyl-ferrocene, α-chloro-β-formyl-p-ferrocenylstyrene, p-ferrocenylphenylacetylene, p-ferrocenylacetophenone, 1,1′-diacetylferrocene and 1,1′-bis[β-(2-furyl)acryloyl]ferrocene which were characterized by spectral and thermodifferential analyses and Hückel MO calculations. The polymerization was performed in the presence of benzoyl and lauroyl peroxides, triisopropylboron and complex catalysts of [P(C₆H₅)₃]₂ NiX₂ type. The ferrocene derivatives were polycondensed with biuret, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl thioether, 4,4′-diamino-2,2′-dinitrodiphenyl disulphide in the presence of metallic salts and p-toluene sulphonic acid as catalysts.Polymers with either linear or tridimensional structure showing good thermal stability and semiconducting properties have been obtained. Some polymers show catalytical activity in the polymerization of chloroformylated vinylic derivatives.     

Heterogeneous oxidation of pyrimidine and alkyl thioethers in ionic liquids over mesoporous Ti or Ti/Ge catalysts

Heterogeneous catalytic oxidation of a series of thioethers (2-thiomethylpyrimidine, 2-thiomethyl-4,6-dimethyl-pyrimidine, 2-thiobenzylpyrimidine, 2-thiobenzyl-4,6-dimethylpyrimidine, thioanisole, and n-heptyl methyl sulfide) was performed in ionic liquids by using MCM-41 and UVM-type mesoporous catalysts containing Ti, or Ti and Ge. A range of triflate, tetrafluoroborate, trifluoroacetate, lactate and bis(trifluoromethanesulfonyl)imide-based ionic liquids were used. The oxidations were carried out by using anhydrous hydrogen peroxide or the urea-hydrogen peroxide adduct and showed that ionic liquids are very effective solvents, achieving greater reactivity and selectivity than reactions performed in dioxane. The effects of halide and acid impurities on the reactions were also investigated. Recycling experiments on catalysts were carried out in order to evaluate Ti leaching and its effect on activity and selectivity.     

Synthesis of new 4-(1-ethylthio-2,2,2-trifluoroethyl)-6-methylpyridazin-3(2H)-ones starting from S-ethyl 4-oxo-2-(pentafluoroethyl)pentanethiolate and hydrazines

The paper presents a one-pot conversion of γ-keto-α-pentafluoroethyl thioester into new pyridazin-3-ones and α,β-unsaturated lactams. The structures of all new compounds were ascribed using 1D (¹⁹F, ¹H, ¹³C) and 2D (¹H-¹⁵N) NMR data, and X-ray diffraction analysis. Two possible competitive reaction mechanisms for the synthesis of pyridazin-3-ones and lactams are presented.     

Gas-phase structures and mass spectra of binary pentafluorides

Most known non-radioactive pentafluorides have been examined by molecular-beam mass spectrometry and by the deflection of molecular beams in inhomogeneous electric fields. Extensive association of the vapors occurs for all but the lighter pentafluorides and the interhalogens. The interhalogen pentafluorides are strongly polar, consistent with the accepted C_4v symmetry. The transition-metal and Group V pentafluorides are all non-polar, except VF₅ and CrF₅ for which temperature-dependent polarity is observed. However, uncertainty exists as to whether these observations are applicable to monomeric pentafluorides in all cases. Mass-spectral cracking patterns are presented for all species.     

Polydisuccinimides: Polyaddition reactions of aliphatic and aromatic diamines to N,N′-bismaleimide

Polyaddition reactions of aliphatic and aromatic diamines to N,N′-bismaleimide and model compounds have been investigated in order to establish some properties of this imide. Glacial acetic acid has a catalytic effect when used as solvent in the preparation of aspartimide compounds. Aromatic diamines show a much smaller reactivity than aliphatic, the former giving polydisuccinimides and the latter polyamides under the same reaction conditions. Addition reactions of N,N′-bismaleimide proceed either by an ionic mechanism in polar solvents or by a homolytic process in solvents precluding ion formation. The thermal stability and the infrared spectra of the new polymers are discussed.