Characterisation of Tokaj wines based on free amino acids and biogenic amines using ion-exchange chromatography

Summary Tokaj wines (Szamorodni and Aszu wines) of Hungarian origin were investigated on the basis of free amino acids and biogenic amines. The separation and determination of these compounds was performed by an amino acid analyser equipped with an ion-exchange resin column. The total amount of free amino acids and biogenic amines was higher in Aszu wines than in Szamorodni wines. The main amino acids were proline and arginine, while the major biogenic amines were tyramine and putrescine. The free amino acid and biogenic amine content of Aszu wines depended on the vineyards the wines originated from. Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001     

Synthesis and modification of 4-hydroxy-2-methyl-3-(2-chloro-2-propenyl)quinoline

4-Hydroxy-2-methyl-3-(2-chloro-2-propenyl)quinoline was prepared by O-allylation of 4-hydroxy-2-methylquinoline followed by the Claisen rearrangement of the 2-methyl-4-(2-chloro-2-propenyloxy)quinoline obtained. Chemical modifications of 4-hydroxy-2-methyl-3-(2-chloro-2-propenyl)quinoline resulted in the synthesis of 4-amino-2-methyl-3-(2-methyl-3-indolyl)quinoline.     

Voltammetry of Formaldehyde at Mechanically Renewable Solid Electrodes

The electrochemical behavior of formaldehyde (CH₂O) at solid electrodes made of platinum, gold, silver, cobalt, nickel, copper, and graphite was studied. The working surface of the electrodes was renewed by cutting a thin layer (0.5 m) immediately in the test solution. It was found that, in alkaline solutions, CH₂O was oxidized at all electrodes other than cobalt and graphite ones while scanning the potential to the anode and cathode regions. The peaks of CH₂O oxidation at platinum and gold electrodes using potential scanning in the anode and cathode directions, as well as at nickel, copper, and silver electrodes using potential scanning in the anodic direction, are suitable for analytical purposes.     

Separation and quantitative determination of dioxouranium(VI) and thorium(IV) ions in the presence of different metallic ions by TLC using iso-propyldithiophosphoric acid as complexing agent

The separation of uranium and thorium from matrices containing various metal ions, was studied. The mobile phase contains isopropyldithiophosphoric acid (i-PrDTP), as a complexing agent, in order to differentiate the studied species by modifying their retention. The paper reports the successful separation and the quantitative determination of uranium and thorium in the presence of Ni²⁺, Co²⁺ and Ag⁺ in the concentration range 2.5–2.5 μg/μl for uranium and 2.5–30 μg/μl for thorium.     

Thermodynamic properties of water/organic systems with small contents of water 1. Limiting partial molal volumes of D2O and H2O in methanol and 2-propanol at various temperatures

Limiting partial molal volumes of D₂O and H₂O in methanol and 2-propanol have been measured in the temperature interval 278–318 K. A hypothesis is advanced regarding the formation of water-alcohol aggregates.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 317–320, February, 1991.     

Aromatic substitution

It is demonstrated that a previously developed topological expression for the total π-electron energy of aromatic molecules provides a good qualitative account of localization energies. The logarithm of the ratio of the algebraic structure counts for the ground state and the localized reaction intermediate is the principle energy determining factor. This expression fails for hydrocarbons with unusually small HOMO-LUMO separations. An alternative topological expression that includes a correction for this situation provides an excellent non-empirical explanation for the successful empirical use of Dewar reactivity numbers in correlating exact localization energies. The present analysis provides an explanation for the success of the traditional resonance structure counting technique in predicting relative rates of aromatic substitution. The analysis develop applied only to alternant hydrocarbons.     

Infrared spectra and rotational isomerism of epifluorohydrin and other propene oxide derivatives

The infrared spectrum for the vapour, liquid and solid states of epifluorohydrin has been studied, and evidence has been obtained for the presence of rotational isomers. The dominant conformer in all phases corresponds to a gauche structure, which was the only form identified in the vapour by microwave spectroscopy [1]. Similar evidence for conformational equilibria has been found for the chloro, bromo and iodo derivatives, and the enthalpy differences between the rotational isomers of these compounds were measured respectively as 4580 ± 970, 3950 ± 400, and 2350 ± 170 J mol^?1 respectively. At low temperatures, epiiodohydrin was found to crystallize in one of two possible crystalline phases. These two phases correspond to the two rotational isomeric conformations of the molecule.     

Reaction of Organoelement Hydrides R<Subscript>3</Subscript>EH (E = Si,Ge) with Metal <Emphasis Type="Italic">tert</Emphasis>-Butylate (M = Al,Ti)-<Emphasis Type="Italic">tert</Emphasis>-Butyl Hydroperoxide Oxidative Systems

Trialkyl(aryl)silanes and -germanes effectively react with metal (Al, Ti) tert-butylate-tert-butyl-hydroperoxide under mild conditions (room temperature, benzene or tetrachloromethane) mainly by the element-hydrogen bond. The character of the products depends on the nature of the element, the structure of the radical bound to it, and the solvent. The process is radical in nature. It includes the stages of formation of element-centered radicals and their reaction with the oxygen generated by the system. The intermediate organometallic peroxides can also acts as oxidants for the element (Si, Ge)-hydrogen bonds.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 7, 2005, pp. 1161–1170.Original Russian Text Copyright © 2005 by Stepovik, Gulenova, Martynova, Skvortsov, Cherkasov.     

Functional derivatives of thiophene

A method is proposed for the synthesis of isatin analogs — 4,5-dioxothieno[2,3-b] pyrroles and 5,6-dioxothieno[3,2-b]pyrroles — by reaction of oxalyl chloride with amino-substituted α-amino- and Β-aminothiophene. The thiosemicarbazones of 4-ary1-5,6-dioxothieno[3,2-b]pyrroles were synthesized. n]mis|See [1] for communication X.     

Reactions of 1-Allenylpyrazole and 1-Allenyl-1,2,4-triazole with Hydrogen Chloride and Metal Chlorides

1-Allenylpyrazole and 1-allenyl-1,2,4-triazole react with hydrogen chloride via proton addition at the pyridine-like nitrogen atom (N² and N⁴, respectively). In the reaction with 1-allenylpyrazole, 1-[(E)-3-chloro-1-propenyl]pyrazole is also formed via regio- and stereoselective addition of hydrogen chloride to the propadienyl group. 1-Allenylpyrazole and 1-allenyl-1,2,4-triazole act as unidentate ligands with respect to Co, Ni, Cu, Zn, Cd, Pd, and Sn, the donor centers being N² and N⁴, respectively. Apart from mononuclear coordination compounds, 1-allenylpyrazole gives rise to polymeric complexes which contain units and blocks formed by the free ligand.