Use of iodide and silver/sulfide ion-selective electrodes for the determination of some tertiary amines and alkaloids

Summary Some tertiary amines and alkaloides were determined by reaction with methyl iodide at 43 °C. The produced quaternary ammonium iodide salts were potentiometrically titrated with standard silver nitrate solution using either the iodide or silver/sulfide ion-selective electrode. The effects of solvent, temperature and time of reaction were examined. An average recovery of 99.0% and 98.9% with standard deviations of 0.73 and 0.52 were obtained for the studied amines and alkaloides, respectively.

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Verwendung der Iodid-bzw. Silber/Sulfid-selektiven Elektrode zur Bestimmung einiger tertiärer Amine und Alkaloide

     

ortho Substituent effect on a 1,5-H shift reaction during thermal decomposition of aryltriazenes

An ortho substituent group has a significant effect on thermal decomposition of aryltriazenes. When the ortho methoxy-substituted phenyltriazenes were treated with methyl iodide at 110-130 °C, 1,5-H shift products were obtained in fair to moderate yields.     

Electrochemical Recovery of Silver from Secondary Raw Materials

Electrolysis of silver in 95-84 wt % sulfuric acid with addition of 40 g l^-1 of silver sulfate was studied at electrolyte temperature of 40°C. The optimal conditions of silver electrolysis in 84-85 wt % sulfuric acid were determined. Semicommercial tests of the electrochemical recovery of silver from silver coatings on copper, brass, aluminum, and steel articles were performed.     

Structure of 2-amino-5-methylthiazoline and its N-methyl derivatives

As indicated by PMR spectroscopic data, 2-amino-5-methylthiazoline and 2-methylamino-5-methylthiazoline exist in the imine form in the temperature interval from +20° to –100° C. Interaction of the 2-amino-5-methylthiazoline with methyl iodide results in alkylation at the endocyclic nitrogen atom.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 415–419, March, 1993.     

High-pressure dissociation of silver mercury iodide, Ag2HgI4

High-pressure X-ray diffraction has been used to probe the behavior of the superionic conductor silver mercury iodide (Ag₂HgI₄) at pressures up to 5 GPa and at temperatures from 295 to 370 K. Significant changes in the diffraction spectra, indicative of structural transitions, are observed around 0.7 and 1.3 GPa across the range of temperatures studied. The change at 0.7 GPa is shown to correspond to the dissociation of silver mercury iodide into silver iodide and mercury iodide, i.e., Ag₂HgI₄→2AgI+HgI₂. The second transition, at 1.3 GPa, is due to a structural phase transition within HgI₂. Rietveld analysis of the diffraction data is used to confirm and refine all the known crystal structures.     

Glass capillary gas chromatography of chlorinated methyl acetates,propanoates and butanoates on Carbowax 20M and SE-30 columns

Summary The gas chromatography of all chlorinated methyl acetates, methyl propanoates and methyl mono- and dichlorobutanoates has been studied on Carbowax 20M and SE-30 glass capillary columns under various running conditions. The order of elution on a non-polar column was largely determined by the boiling point of esters, whereas on a polar column it was much influenced by the structure of compounds. Complete separation of the combined mixture of all 27 compounds could not be achieved, however, methyl 3,3-dichlorobutanoate was the only ester overlapped on both columns in spite of the various column temperatures used. The best separation of the mixture was on Carbowax 20M with a temperature program from 50°C at 8°C/min, isothermal running conditions leading either to poor separation of volatile components or long analysis time and broad peaks of higher chlorinated esters. The relative retention times for compounds at the various column temperatures are given and the retention order on a polar and on a non-polar column discussed.     

3-Oxo-3-thia-2-azabicyclo[2.2.1]hept-5-en-2-carboxylates: the first isolation and characterization

Methyl and benzyl 3-oxo-3-thia-2-azabicyclo[2.2.1]hept-5-en-2-carboxylate were isolated at rt and characterized for the first time. Both endo and exo-isomers were observed. Under suitable experimental conditions (stoichiometric amount of sodium acetate, −40 °C or sodium borohydride/methyl iodide) ring opening of these compounds gave the corresponding thiosulfonates or methyl sulfides, respectively.     

Thermal decomposition process of silver behenate

The thermal decomposition processes of silver behenate have been studied by infrared spectroscopy (IR), X-ray diffraction (XRD), combined thermogravimetry-differential thermal analysis-mass spectrometry (TG-DTA-MS), transmission electron microscopy (TEM) and UV-vis spectroscopy. The TG-DTA and the higher temperature IR and XRD measurements indicated that complicated structural changes took place while heating silver behenate, but there were two distinct thermal transitions. During the first transition at 138 °C, the alkyl chains of silver behenate were transformed from an ordered into a disordered state. During the second transition at about 231 °C, a structural change took place for silver behenate, which was the decomposition of silver behenate. The major products of the thermal decomposition of silver behenate were metallic silver and behenic acid. Upon heating up to 500 °C, the final product of the thermal decomposition was metallic silver. The combined TG-MS analysis showed that the gas products of the thermal decomposition of silver behenate were carbon dioxide, water, hydrogen, acetylene and some small molecule alkenes. TEM and UV-vis spectroscopy were used to investigate the process of the formation and growth of metallic silver nanoparticles.     

Anion exchange behaviour of the transplutonium and rare earth elements in nitric acid — Methyl alcohol media at elevated temperature

Anion exchange behaviour of the transplutonium (Am, Cm and Cf), rare earth (Y, Ce, Pm and Eu) and some other elements (U, Al, Sr and Cs) has been investigated in nitric acid-methyl alcohol media at temperatures up to 90°C. Distribution coefficients and separation factors of the elements were determined in the media at 90°C as a function of concentrations of nitric acid and methyl alcohol. Separation factors decrease significantly but the resolution of eluted elements improves with increasing temperature. Chromatographic separation of those elements was rapidly performed by using a very small column at 90°C. The effluent of the column received on a metal disk can be readily evaporated and one may immediately prepare samples for alpha-ray spectrometry.     

Thermal decomposition of natural and synthetic plumbojarosites: Importance in ‘archeochemistry’

Plumbojarosite and argentoplumbojarosite were sources of lead and silver in ancient and medieval times. The understanding of the chemistry of the thermal decomposition of these minerals is of vital importance in ‘archeochemistry’. The thermal decomposition of plumbojarosite was studied using a combination of thermogravimetric analysis coupled to a mass spectrometer. Three mass loss steps are observed at 376, 420 and 502 °C. These are attributed to dehydroxylation, loss of sulphate occurs at 599 °C, and loss of oxygen and formation of lead occurs at 844 and 953 °C. The temperatures of the thermal decomposition of the natural jarosite were found to be less than that for the synthetic jarosite. This is attributed to a depression of freezing point effect induced by impurities in the natural jarosite. Raman spectroscopy was used to study the structure of plumbojarosite. Plumbojarosites are characterised by stretching bands at 1176, 1108, 1019 and 1003 cm⁻¹ and bending modes at 623 and 582 cm⁻¹. Changes in the molecular structure during thermal decomposition were followed by infrared emission spectroscopy. The technique shows the loss of intensity in the hydroxyl stretching region attributed to dehydroxylation. Loss of sulphate only occurs after dehydroxylation. Lead is formed at higher temperatures through oxygen evolution.     

Synthesis of14C-propoxur (o-isopropoxyphenyl N-methylcarbamate-14C) insecticide

Propoxur (Baygon^®) is an insecticide with a broad spectrum of activity and a very low order of mammalian toxicity. Radiosynthesis of propoxur was performed by the reaction of acetyl-1¹⁴C chloride and sodium azide to produce methyl isocyanate which then reacted with o-isopropoxyphenol at 100°C. A two compartment reaction tube with a break seal was utilized. Chromatographic procedures for isolating the N-methylcarbamates from their reaction mixtures are reported. Acetyl-1–¹⁴C chloride was prepared from thionyl chloride and sodium acetate-1–¹⁴C. Grignard reaction between methyl iodide and carbon –14 dioxide yielded acetic acid –¹⁴C which was neutralized by sodium hydroxide solution to give sodium acetate 1-¹⁴C.     

Complex Formation of Crown Ethers with Cations in Water–Organic Solvent Mixtures. III. Thermodynamics of Interaction Between Na+ Ion with 15-Crown-5 Ether in Water–Acetonitrile Mixtures at 25°C

Enthalpies of solution of 15-crown-5 ether in the acetonitrile–water–sodium iodide system have been measured at 25°C. The equilibrium constants of complex formation of 15C5 with sodium iodide have been determined by molar conductance at various mole ratios 15C5 to sodium iodide in mixtures of water with acetonitrile at 25°C. The thermodynamic functions for complexation of the crown ether with Na⁺ were calculated. From the result, the standard Gibbs energies of complex formation as a function of the normalized Lewis acidity parameters E ^N _T and enthalpy of solvation of 15C5 in the mixtures of water with acetonitrile have been analyzed. The enthalpies of transfer of the 15C5 complex with sodium iodide from pure acetonitrile to the mixtures studied were calculated and discussed.     

甲基锍盐的合成

在四氟硼酸银存在下，分别以硫醚、硫醇、硫酚或过硫醚为原料与碘甲烷反应制备了相应的甲基锍盐。用１ＨＮＭＲ和１３ＣＮＭＲ表征产物的结构并提出了反应的机理。     

Thermal oxidation of poly(1-trimethylsilylprop-1-yne) studied by IR spectroscopy

Thermal oxidation of poly(1-trimethylsilylprop-1-yne) was studied by IR spectroscopy in the 20—245 °C temperature interval. In the 20—160 °C temperature range, the reaction proceeds predominantly at the C—Me group as revealed by the decrease in the intensity of the bands of the methyl group bound to the C atom and the appearance of the bands of the hydroperoxide and methylene groups. The decomposition of hydroperoxides produces aldehydes and ethers. At 160—200 °C, oxidation occurs via two routes: at the C—Me and C=C groups, while the Me₃Si group remains unchanged. At 230—240 °C, the rate of the reaction occurring at the C=C bond is higher than the rates of the processes involving the MeC and Me₃Si groups. The relative content of the structural units was calculated for the samples oxidized at different temperatures. Plausible mechanisms of thermal oxidation of poly(1-trimethylsilylprop-1-yne) were considered on the basis of the data obtained.     

Annealing Behavior of Silica Gel Powders Modified with Silver Crystalline Aggregates

The annealing behaviour of silica powders added with silver, prepared by the sol-gel method, was studied using X-ray diffraction. Partial crystallization of amorphous SiO₂ samples as low as 600°C has been observed. For that, silver needed to be added to the precursor solution in such a way that it formed aggregates. Silica xerogel samples were prepared using a molar ratio ethanol/H₂O/TEOS of 4:11.6:1 and loaded with silver in three different ways: in the form of silver nitrate, silver chloride, or chemically synthesised silver fine particles. The microstructure of the silica xerogel powders was studied as a function of annealing temperature. Attention was paid to the evolution of the glass matrix as well as the silver aggregates in the SiO₂ matrix. Partial crystallization of the glass matrix was achieved at temperatures much lower than those specified by the phase diagram, independently of preparation method of the silver aggregates.     

Application of Alumina Aerogels as Catalysts

Al₂O₃ gels prepared by hydrolysis of Al-alkoxide were applied as catalysts for NO reduction by hydrocarbon. Xerogels were obtained by drying at 90°C, for 24 h, in air. Aerogels were prepared by supercritical drying of the wet gels in ethanol, using an autoclave. The catalyst activity of the gels for NO reduction with C₃H₆ as determined at 200–600°C in a fixed bed flow reactor. NO conversion to N₂ was about 60% at 550°C with both catalysts, and at 600°C it was better with the aerogel than with the xerogel. The specific surface area of the xerogel, which was larger than that of the aerogel as-dried, decreased to 1/3 by annealing at >500°C. However, the surface area of the aerogel hardly changed by annealing at temperatures up to 700°C. The bimodal pore size distribution of the aerogel hardly changed by annealing, too. The microstructure of the aerogels is stable at high temperatures, and they are better catalysts at high temperatures.     

Dual Effect of Organomercury Compounds on Peroxide Oxidation of Oleic Acid

Oxidation of oleic acid with atmospheric oxygen in the presence of HgCl₂ and various organo- mercury compounds (methylmercury iodide, isopropylmercury bromide, n-hexylmercury bromide, phenylmercury bromide, diphenylmercury, p-tolylmercury bromide, bis-p-tolylmercury) was studied. Mercury compounds exert a dual effect on accumulation of oleic acid hydroperoxide in the temperature range 20-90°C. Below 50°C, the concentration of the hydroperoxides formed in the presence of mercury compounds is lower, and at higher temperatures, higher than in the experiments performed without mercury compounds. Comparison of the concentrations of oleic acid hydroperoxides with those of their transformation products, carbonyl compounds, determined spectrophotometrically, shows that actually organomercury compounds and HgCl₂ accelerate peroxide oxidation at all the studied temperatures. Decreased accumulation of peroxides below 50°C is apparently due to the fact that the rate of their reaction with organomercury compounds is higher than the rate of their formation.     

The [1,2]-thio-Wittig rearrangement: evidence for a radical mechanism and its suppression

The lithium enolate formed from methyl S-trityl mercaptoacetate can be C-alkylated in high yield at or below −40 °C, but at higher temperatures the [1,2]-thio-Wittig rearrangement of the enolate is the predominant process; ESR evidence indicates that this rearrangement occurs by a radical mechanism.     

Application of cinchona-sulfonate-based chiral zwitterionic ion exchangers for the separation of proline-containing dipeptide rotamers and determination of on-column isomerization parameters from dynamic elution profiles

The interconversion of cis and trans isomers of dipeptides containing C-terminal proline was studied by dynamic chromatography on zwitterionic chiral stationary phases at temperatures ranging from −15 °C to +45 °C The cis–trans isomers could be separated below 0 °C and above 0–10 °C plateau formation and peak coalescence phenomena occurred, which is characteristic for a dynamic process at the time-scale of partitioning. At and above room temperature, full coalescence was observed, which allowed separations of enantiomers without interference from interconversion effects. Analysis of the dynamic elution profiles of the interconverting peptides allowed the determination of isomerization rate constants and thermodynamic activation parameters (isomerization enthalpy, entropy and activation energy). In accordance with established results, isomerization rates and thermodynamic parameters were found to depend on the nature of the N-terminal amino acid. Isomerization barriers were only slightly lower than values determined with other methods but significant differences in the relative contributions of the activation enthalpy and entropy as well as isomerization rates pointed toward selector-moderated isomerization dynamics.