Quantum-Chemical Calculations of the Reaction of Haloalkynes with Grignard Compounds

Two pathways of the reactions of methylmagnesium bromide with 1-chloro- and 1-bromo-3-methoxymethyl-1-propynes were simulated by the MNDO quantum-chemical method. The calculations predict initial coordination of magnesium to the C atom of the triple bond, which determines predominant nucleophilic substitution of the halogen atom according to the addition-elimination pattern.     

Concentration dependence of the surface tension of ternary systems

A surface tension isotherm equation for ternary systems was derived based on general thermodynamic expressions with consideration for the concentration dependence of the molar surface area. Within the experimental errors, the equation describes the properties of ternary systems with smooth surface tension isotherms.     

Thermal stability of segmented polyurethanes

The thermal stabilities of two series of segmented polyurethane fibres have been compared with their chemical structure. The polyurethanes were synthesized from trimethylene diamine; 4, 4′ diphenylmethane di-isocyanate and two polyether based macrodi-isocyanates. Thermal stability was measured by thermogravimetric analysis and differential thermal analysis. By comparing the changes in weight loss and DTA peaks with chemical structure it has been found possible to separate soft segment from hard segment degradation.In the initial stages stability increases as soft segment concentration increases while the reverse is true in the later stages of degradation. The 100% soft segment polymer (polytetrahydrofuran) and the 100% hard segment polymer appear to behave anomalously. It is suggested that the hard segment has a stabilizing influence on the degradation of the soft segment. The results are discussed in the light of various theories of polyurethane degradation.     

Epitope extraction technique using a proteolytic magnetic reactor combined with Fourier-transform ion cyclotron resonance mass spectrometry as a tool for the screening of potential vaccine lead peptides

Epitope extraction technique is based on the specific digestion of a target protein followed by immunoaffinity isolation of a specific recognition peptide. This technique, in combination with mass spectrometry, has been efficiently used for epitope identification. The major goal of this work was to utilize newly developed enzyme and immunoaffinity magnetic reactors for the epitope extraction procedure and confirm the efficiency of this improved system for epitope screening of proteins. Alginic acid-coated magnetite microparticles with immobilized TPCK-trypsin provided high working efficiency with low non-specific adsorption, digestion time in minutes and low frequency of missed cleavages. The sensitivity and specificity of tryptic fragmentation of the beta-amyloid-peptide Abeta (1-40) as a model polypeptide was confirmed by Fourier-transform ion cyclotron resonance mass spectrometry analysis. The Sepharose reactor or immunoaffinity magnetic reactors, both with anti-amyloid-beta monoclonal antibodies, were used for specific isolation and identification of target peptides. In this way, the epitope extraction technique combined with mass spectrometric analysis is shown to be an excellent base for molecular screening of potential vaccine lead proteins.     

Determination of acetone, 2-butanone, diethyl ketone and BTX using HSCC-UV-IMS

A combination of a custom-designed ion mobility spectrometer (IMS) with a UV ionization source and a high speed capillary column (HSCC) has been developed as an analytical device for the sensitive detection of volatile organic compounds (VOCs), e.g. 2-propanone (acetone), 2-butanone and 3-pentanone (diethyl ketone) in the gas phase. A fast separation of the three selected substances and benzene, toluene and m-xylene (BTX) - all of which occur in human breath - has been achieved within less than four minutes at a carrier gas flow rate of 4.5 mL x min(-1). Multi-dimensional correlations presented support the interpretation of the acquired spectra of mixtures. Method detection limits were 2.7 microg x L(-1) for acetone and 2-butanone and 3.0 microg x L(-1) for diethyl ketone in nitrogen, respectively. The assay linear dynamic range is 4-320 microg x L(-1).     

Thermal decomposition of rare earthp-aminosalicylates in air atmosphere

The conditions of thermal decomposition of thep-aminosalicylates of Y, La and the lanthanides from Ce(III) to Lu have been studied. On heating, the hydrated complexes of La and the light lanthanides decompose to the oxides with the intermediate formation of Ln₂[H₂N·C₆H₃(O)COO]₃. Only the complex of La decomposes to La₂O₃ through La₂[H₂N·C₆H₃(O)COO]₃ and La₂O₂CO₃. The anhydrous complexes of the heavy lanthanides decompose directly to the oxides, whereas the anhydrous complex of Y decomposes to Y₂O₃ via Y₂[H₂N·C₆H₃(O)COO]₃ formation. During heating, the hydrated complexes lose crystallization water and decompose simultaneously, and the endothermic effect of dehydration is masked by the strong exothermic effect of burning of the organic ligand.

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Zusammenfassung Es wurden die Bedingungen für die thermische Zersetzung derp-Aminosalicylate von Y, La und der Lanthanoide von Ce(III) bis Lu untersucht. Beim Erhitzen zersetzen sich die hydratierten Komplexe von La und der leichteren Lanthanoide unter Bildung des Zwischenproduktes Ln₂[H₂NC₆H₃(O)COO]₃ in ihre Oxide. Nur der Komplex mit La zersetzt sich zu La₂O₃ über die Zwischenstufen La₂[H₂NC₆H₃(O)COO]₃ und La₂O₂CO₃. Die wasserfreien Komplexe der schweren Lanthanoide zersetzen sich direkt in die Oxide, wÄhrend sich der wasserfreie Komplex von Y über die Bildung von y₂[H₂NC₆H₃(O)COO]₃ in y₂O₃ zersetzt. Beim Erhitzen verlieren die hydratierten Komplexe ihr Kristallwasser und zersetzen sich gleichzeitig, der endotherme Effekt der Dehydratation wird durch den starken exothermen Effekt der Verbrennung der organischen Liganden überdeckt.

     

Photoelectron spectra andab initio calculations of the electronic structure of amino-n-sulfenyl chlorides

The electronic structure of some amino-N-sulfenyl chlorides and related compounds is studied by photoelectron spectroscopy and ab initio calculations. Similar values of IP(n _S ) and IP(n _N ) and the total energy minimum indicate that in stable conformations the n _S and n _N orbitals are orthogonal. These conformers are characterized by an effective n_N-σ _S-Cl ^* interaction. The relationship between the intramolecular shift of charge and ionization potential values and the spatial structure of amino-N-sulfenyl chlorides is analyzed. A. E. Arbuzov Institute of Organic and Physical Chemistry, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 2, pp. 69–73, March–April, 1994. Translated by L. Smolina     

Synthesis and acute toxicity of some phosphorylated derivatives of ephedrine alkaloids

The results are given of the synthesis and a comparative study of the toxicities of some phosphorylated derivatives of the alkaloids l-ephedrine and d-pseudoephedrine. It has been shown that the introduction of phosphorus- and sulfur-containing fragments considerably lowers the toxicity of the alkaloids. Institute of Organic Synthesis and Coal Chemistry, National Academy of Sciences of the Republic of Kazakhstan, Karaganda. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 406–408, May–June, 1994.