A method for bulk hydrogen analysis based on transmission and back scattering of fast neutrons

A method was proposed for bulk hydrogen analysis. It is based on simultaneous detection of transmitted fast neutrons and back scattered thermal neutrons from the investigated samples by ³He detectors. The fast neutron beams were obtained from ²⁵²Cf and Pu–Be neutron sources. The experimental set-up as well as samples preparation were described. Incident thermal neutrons beams obtained from either ²⁵²Cf or Pu–Be sources, were used to investigate the samples by neutron backscattering. The results obtained from transmission and backscattering of fast neutrons were compared and discussed. The advantage and capabilities of the proposed method were presented. The results obtained using fast neutron beams are more sensitive than those obtained using thermal neutron beams. Validation procedures were proposed to credit the results.     

Natural pyrite as an electrochemical sensor for potentiometric titrations with EDTA, mercury(II) and silver(I)

The results obtained in potentiometric titrations of copper(II), mercury(II) and iron(III) with standard EDTA solutions are presented. The titration of copper(II) at pH values in the range from 8.11 to 10.99 (ammonia buffer) and the titration of mercury(II) and iron(III) at pH values from 3.59 to 5.65 (acetate buffer) were performed. The titration end-point (TEP) was detected with an indicator electrode made from natural crystalline pyrite as an electrochemical sensor. The results obtained in potentiometric titration with the pyrite electrode were compared with those obtained using a platinum electrode (Fe³⁺), a Cu ion selective electrode (Cu²⁺) and a Hg electrode (Hg²⁺). Accurate and reproducible results with good agreement were obtained, but higher potential changes at the TEP were obtained using the pyrite electrode. In the course of the titration the potential was established within less than 1 min, whereas at the TEP it was within about 2–3 min. The potential changes at the TEP were in the range from 60 to 200 mV per 0.1 ml EDTA, according to the stability constant of the complex formed. The highest potential changes, ranging from 160 to 200 mV, were obtained in the titration of iron(III) at pH 3.59. Reverse titration was also performed and accurate and reproducible results were obtained. Moreover, titration of halogenide and thiocyanate with standard mercury(II) solutions, as well as cyanide with silver(I) solution, were performed and accurate and reproducible results were again obtained. Received: 20 February 1998 / Accepted: 19 November 1999     

Synthesis of oxime bearing cyclophosphazenes and their reactions with alkyl and acyl halides

Two novel cyclophosphazenes containing oxime groups were prepared from the hexakis(4‐formylphenoxy)cyclotriphosphazene ( 2 ) and hexakis‐(4‐acetylphenoxy)cyclotriphosphazene ( 7 ). The reactions of these oximes with acetyl chloride, chloroacetyl chloride, methyl iodide, propyl chloride, mono‐ chloroacetone, and 1,4‐dichlorobutane were studied. Hexasubstituted compounds were obtained from the reactions of hexakis(4‐[(hydroxyimino)methyl]phenoxy)cyclotriphosphazene ( 3 ) with acetyl chloride ( 4 ) and chloroacetyl chloride ( 5 ); however, tetrasubstituted product was obtained from methyl iodide ( 6 ). Tetra‐ and trisubstituted products were obtained from the reactions of hexakis(4‐[(1)‐N‐hydroxyethaneimidoyl]phenoxy)cyclotriphosphazene ( 8 ) with acetyl chloride ( 9 ) and chloroacetyl chloride ( 10 ), respectively. All products were obtained in high yields. Pure and defined product could not be obtained from the reaction of 8 with methyl iodide, and could not be also obtained from the reactions of 3 and 8 with propyl chloride, monochloroacetone, and 1,4‐dichlorobuthane. The structures of the compounds were defined by elemental analysis, IR, ¹H, ¹³C, and ³¹P NMR spectroscopy. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:112–117, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20176     

Synthesis of 2-propyloxazole and 2-propyloxazole-4-carboxylic acid derivatives

2-Propyloxazole (VI) was obtained in a number of steps starting from butyronit rile. The hydrazide and amide were obtained from ethyl 2-propyloxazole-4-carboxylate; the amide was converted to the nitrile, from which the thioamide and amidoxime were obtained by the usual method. Attempts to convert VI to 2-propylisonicotinic acid or its nitrile by the reaction of VI with acrylic acid or acrylonitrile did not give positive results.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 7–9, January, 1972.     

Effect of Microwave Activation on Polymerization Rate and Molecular Weight Development in Emulsion Polymerization of Methyl Methacrylate

Polymerization rate and molecular weight development experimental results for the emulsion polymerization of methyl methacrylate (MMA), in the presence of potassium persulphate (PPS) as initiator, and activated with a 50 W microwave source, are reported. The polymerization kinetics of the microwave activation experiment (MA) was compared against a traditional conductive heating (CH) polymerization reaction. The number average molecular weights, M_n, of the polymer samples obtained with microwave activation were significantly higher than those obtained from conductive heating. These high values of M_n were obtained from the beginning of the polymerization reaction. Polydispersity index (PDI) values in the range of 1.18 to 1.83 were obtained in the microwave irradiated samples. These values are lower than those produced by conventional emulsion polymerization of styrene and other vinyl monomers, and resemble the PDI values obtained in controlled‐radical polymerization processes. Polymer particles of submicron size (60 to 100 nm) were obtained.     

Synthesis of o-azobispyrazole derivatives

Azobispyrazoles were obtained by diazo coupling of diazotized o-aminoazopyrazoles. The o-azobispyrazole obtained from 3-methyl-1-phenyl-5-pyrazolone exists in the o-azohydrazone form, whereas the o-azobispyrazole obtained from 5-amino-3-methylpyrazole exists in the o-azobis form. A 3-azo derivative of naphtho[2,1-e]-pyrazolo[5,1-c]triazine is formed from 2-naphthol. The structures of the compounds obtained were confirmed by IR, UV, PMR, and mass spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 382–387, March, 1978.     

Atomic transition probabilities for selected Yb II lines emitted from a ferroelectric plasma source

The relative intensities of several hundred emission lines of Yb II between 200 nm and 900 nm were obtained with the use of ferroelectric plasma source. These relative intensities obtained for lines from 21 energy levels have been used to determine the line branching fractions, which have then been combined with accurate experimental radiative lifetime measurements to give absolute transition probabilities for 111 Yb II lines. The obtained values were compared with theoretical and experimental data taken from available literature.     

In-situ detection of single particles of explosive on clothing with confocal Raman microscopy

Confocal Raman microscopy is shown to detect picogram quantities of explosives in-situ on undyed natural and synthetic fibres, and coloured textile specimens leaving potentially evidential materials unaltered. Raman spectra were obtained from pentaerythritol tetranitrate (PETN), trinitrotoluene (TNT), and ammonium nitrate particles trapped between the fibres of the specimens. Despite the presence of spectral bands arising from the natural and synthetic polymers and dyed textiles, the explosive substances could be identified by their characteristic Raman bands. Furthermore, Raman spectra were obtained from explosives particles trapped between highly fluorescent clothing fibres. Raman spectra were collected from explosives particles with maximum dimensions in the range 5-10 μm. Spectra of the explosives on dyed and undyed clothing substrates were readily obtained in-situ within 90 s and without sample preparation.     

Mesoionic 2-acylimino-1,3,4-thia- and -oxadiazoles

2-Acylimino-1,3,4-thiadiazoles were obtained from 1-methyl-1-thioacylhydrazines and the appropriate acyl isothiocyanates, while 2-benzoylimino-1,3,4-oxadiazole was obtained from 1-phenyl-1-benzoylhydrazine and benzoyliminocarbonic acid dichloride. The mesoionic structure of the compounds obtained was proved by their IR and mass spectra. Reduction, hydrolysis, and salt-formation reactions of them were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1345–1350, October, 1973.     

Chemical structure and surface properties of the polyurethane cationomers

Polyurethane cationomers were synthesised in the reaction of various diisocyanates with polyoxypropylene glycol and two N-alkyldiethanolamines. The obtained isocyanate prepolymers were then extended in the aqueous medium by means of 1,6-hexamethylenediamine; stable aqueous dispersions were thus obtained, which were applied to and distributed over the poly(tetrafluoroethylene) surface. After evaporation of water from those dispersions, thin polymer coatings were produced. The analyses with the use of ¹H, carbon-13 nuclear magnetic resonance and infrared spectroscopy methods confirmed chemical structures of synthesised cationomers. Also, attempts were made to quantitatively characterise polarities of those structures by means of factors that were defined especially for that purpose. Moreover, the physical model of van Oss–Good and wetting angles for coatings obtained from the polyurethane cationomers in question, measured with the use of standard liquids with various polarity specifications, were utilised to determine the surface free energy values for the obtained ionomers.     

Determination of antihypertensive mixtures by use of a chemometrics-assisted spectrophotometric method

A simple multivariate calibration method for analysis of two types of hypotensive mixture is described. The mixtures are composed of chlorthalidone with atenolol or chlorthalidone with both amiloride hydrochloride and atenolol. The components of the mixtures result in substantial spectral overlap—between 87.5 and 91.0%. Resolution of the mixtures under investigation has been accomplished mainly by using CLS and PCR methods. The components in each mixture have been simultaneously determined in three commercial dosage forms with high accuracy and without interference from commonly encountered excipients and additives. Good recoveries were obtained with both synthetic mixtures and commercial tablets. The results obtained were compared with those from pharmacopeial methods and found to be in good agreement. The results obtained from CLS and PCR were also compared with those obtained from a ¹D spectrophotometric method.     

Applications of HPLC-MS in compound Ilex pubescens extract study

In this paper, high performance liquid chromatography (HPLC) along with mass spectrometry (MS) and HPLC along with a diode array detector (DAD) was used to study the compound Ilex pubescens extract. Two ionization techniques: electro spray ionization (ESI) and atmospheric pressure chemical ionization (APCI) were used in this work. The liquid chromatograms obtained by DAD, total ion chromatograms (TIC) from positive-and negative-ion ESI-MS and the positive-and negative-ion APCI-MS were compared. The liquid chromatograms obtained by TIC from ESI-MS provided more information on chromatographic peaks than those obtained by DAD or TIC from APCI-MS. It is suggested that the fingerprints of the compound Ilex pubescens extract should be provided by the liquid chromatograms obtained by DAD together with TIC from the negative-ion ESI-MS. The molecular weights of the nine main components in an HPLC-DAD chromatogram were determined by the corresponding positive-and negative-ion ESI and the positive-and negative-ion APCI mass spectra information. In the liquid chromatogram obtained by TIC from the negative-ion ESI-MS, the molecular weights of 23 main components were determined based on the corresponding positive-and negative-ion ESI mass spectra information.     

9-Imino(amino)-10-sila-2-azaanthracenes

9-Imino derivatives of dihydrosilaazaanthracenes were obtained from 10,10-diorganosila-2-azaanthrones. It was shown by PMR spectroscopy that they exist in the form of Z and E isomers. The azomethines were reduced to secondary amines, from which the N-acyl derivatives were obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 126–129, January, 1989.     

Investigation of molecular and chiroptical characteristics of optically active functional vinyl copolymers possessing main-chain chirality

Optically active styrene-methyl methacrylate and styrene-methacrylonitrile copolymers were obtained by template assisted asymmetric copolymerization of 3,4-cyclohexyhdene-D-mannitol-1,2;5,6-bis-O[(4-vinylphenyl)boronate] ( 1 ) with the corresponding comonomers followed by removal of the template and deboronation. By polymer analog modification methods, several optically active functional copolymers were obtained starting with these copolymers. The resulting polymers were subjected to different types of spectroscopic analysis. Thus, the results obtained from IR, ¹³C-NMR and GPC were of great value for detailed structural analysis of these polymers providing both qualitative and quantitative informations in terms of mode and neatness of substitution and degree of functionalization. The chiroptical measurement results obtained from circular dichroic (CD) studies have been utilized to analyze precisely the substituent dependent local solution stereochemistry of these chiral polymers. © 1992 John Wiley & Sons, Inc.     

Re-Evaluation of the Activity Coefficients of Aqueous Hydrochloric Acid Solutions up to a Molality of 2.0 Using Two-Parameter Hückel and Pitzer Equations. Part I. Results at 25°C

Simple two-parameter Hückel and Pitzer equations were used for the calculation of the activity coefficients of aqueous hydrochloric acid at 25°C up to a molality of 2.0 mol-kg^–1. The data obtained by Harned and Ehlers^(12,13) from galvanic cells without liquid junction were used in the analysis and the parameters obtained were compared to those obtained from all reliable data presented in the literature for HCl at this temperature. A good agreement between the parameters was always observed. The activity coefficients obtained by the new equations were compared to those suggested by Robinson and Stokes,⁽⁸⁾ Hamer and Wu,⁽¹⁾ and Pitzer and Mayorga,⁽⁹⁾ and good agreement was also found. The data from the most important literature data sets for HCl were also predicted using the new activity coefficient equations, and the magnitude of the resulting errors was close to the precision of the measurements, the errors forming an almost random pattern for all data sets.     

Preparation of 4,6-diaminopyrazolo[3,4-d] pyrimidines with variations in substitution at the 1- and 3-positions

A number of new derivatives of 4,6-diaminopyrazolo[3,4-d]pyrimidines substituted in the 1- and/or 3-positions have been obtained from reactions of guanidine carbonate with 1- and/or 3-substituted-5-amino-4-cyanopyrazoles. Use of triethanolamine as a reaction medium permitted preparation of certain derivatives which could not be obtained from the previously described fusion procedure. Some derivatives of 4-aminopyrazolo[3,4-d]pyrimidine with substitution at the 1 - and/or 3-positions were also obtained from reactions of formamide with the same 5-amino-4-cyanopyrazoles. The new compounds were screened for in vivo antimalarial activity, but were found inactive.     

Negative pion transfer process in a hydrogen-containing gas mixture

Annihilation γ-rays of π⁰ and pionic X-rays were measured in the gas mixtures of H₂+Z and CH₄+Z systems (Z=He, Ne, Ar and Kr). Pion capture probability of hydrogen atom was obtained from the annihilation γ-ray counts and the capture probability of Z atom was obtained from the pionic X-ray intensities. Transfer rates were determined from the data based on a combined large mesomolecular model. The transfer rates obtained were smaller than the systematics of the Russian group. Difference in the transfer rate between the gas and the liquid phases was found by a comparison of the present results with our previous ones.     

A Simple Method for Determining the Critical Micellar Concentration of a Surfactant

This paper will present a simple method for critical micellar concentration (cmc) determination based on light scattering using a turbidimeter. The method does not require the optical clarification of the surfactant solution. The surfactant solutions were prepared from distilled water after boiling. Distinct cmc values were observed for polyoxyethylene mono n-dodecylether, sodium taurodeoxycholate and sodium dodecyl sulfate. The cmc values obtained using the turbidity method were compared with cmc values obtained by the surface tension method and with data given in the literature. Values obtained by our simple method have comparable accuracy with data obtained from more elaborate experiments.     

Synthesis and some transformations of 1, 2, 3, 4-tetrahydrophenothiazine derivatives

1,2,3,4-Tetrahydrophenothiazine derivatives were obtained from cyclic monoketones and 1,3-diketones and o-nitroarenesulfenyl chlorides. The alkylation, aminomethylation, and oxidation of the compounds obtained were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1509–1513, November, 1972.     

Polycyclic Phosphorus-Containing Oxaboracyclanes

Abstract

The olygomers consisting of regularly repeating heterocyclic fragments were synthesized by the reaction of polycondensation of the ether of p-phenylenediboric acid and tetraoxymethyloldphosphioes obtained from the different diphosphines and aldehydes. The compounds with endocyclic phosphorus atom (I) were obtained in case of using the aliphatic aldehydes, and the compounds with exocyclic phosphoruscontaining group (II) were obtained when using the hydroxyaldehydes.