Determination of 2-mercaptobenzothiazole in river water by HPLC

Summary A method is proposed for the determination of 2-mercaptobenzothiazole in river waters using multi-electrode electrochemical detection HPLC. 2-mercaptobenzothiazole determination is unsatisfactory by gas chromatography as it degrades readily on the column. Multielectrode electrochemical detection HPLC combines sensitivity and the ability to screen out other electrochemically active species. The development work leading up to the proposed method is discussed. The method has a limit of detection of 0.798gl^–1 2-mercaptobenzothiazole and a total standard deviation of 2.06gl^–1 2-mercaptobenzothiazole at a concentration of 7.97gl^–1 2-mercaptobenzothiazole in river water.     

Direct Synthesis of H2O2 by a H2/O2 Fuel Cell

Direct synthesis of H₂O₂ solutions by a fuel cell method was reviewed. The fuel cell reactor of [O₂, gas-diffusion cathode electrolyte solutions Nafion membrane electrolyte solutions gas-diffusion anode, H₂] is very effective for formation of H₂O₂. The three-phase boundary (O₂(g)–electrode(s)–electrolyte(l)) in the gas-diffusion cathode is essential for efficient formation of H₂O₂. Fast diffusion processes of O₂ to the active surface and of H₂O₂ to the bulk electrolyte solutions are essential for H₂O₂ accumulation. The maxima H₂O₂ concentrations of 1.2 M (3.5 wt%) and 2.4 M (7.0 wt%) were accomplished by the heat-treated Mn-OEP/AC electrocatalyst with H₂SO₄ electrolyte and by the VGCF electrocatalyst with NaOH electrolyte, respectively, under short circuit conditions.     

Preparation of spherical,mixed SiO2/TiO2 particles by the sol technique

Preparation of silica, titania and mixed silica/titania particles has been studied. The region for formation of monodisperse SiO₂ particles in the phase diagram tetraethyl orthosilicate (TEOS)-ethanol-H₂O was studied as a function of NH₃ concentration at room temperature. Titania particles could be prepared at lowered temperatures and concentration of ammonia up to 0.01 M. The size of SiO₂ particles was 0.03–1 m whereas TiO₂ particles were size range 0.5–0.8 m. Mixed SiO₂/TiO₂ particles were prepared from prehydrolyzed TEOS/EtOH solutions by adding tetraethyl orthotitanate (TEOT). This was accomplished at 3°C and slightly alkaline solutions. The final particle size of the mixed particles was about 0.3 m.     

Hartree Fock instabilities of sulfur-nitrogen ring systems: S2N2

The Hartree-Fock instablities of S₂N₂ are reported and compared with those of S₃N and S₄N. These unsaturated sulfur nitrogen planar rings are π electron rich and although the symmetry adapted HF solutions are singlet stable at the experimental bond lengths they become unstable with only a very modest increase in bond length. The broken symmetry solutions for S₂N₃, S₃N, and S₄N are of planar C_2v type with one of the nitrogens stripped of its π electrons, producing a π hole.     

Deuterium kinetic isotope effect in the oxidation of sodium (2-D2)valerate with manganate in 3M aqueous NaOH solutions

Sodium (2-²H₂)valerate has been obtained by exchange technique and the kinetic parameters characterizing the oxidation of both sodium valerate of normal isotopic composition and sodium ,-dideuteriovalerate with manganate in 3M aqueous NaOH solutions have been determined. A discussion of the kinetic deuterium isotope effect observed in the oxidation of CH₃CH₂CH₂CD₂COONa is given.     

Phase Equilibria in the System CuO-Fe2O3-Sb2O4-O2

Results of X-ray phase analysis were used to construct the phase diagram of the system CuO-Fe₂O₃-Sb₂O₄-O₂ at 1000°C in air. Two Cu_2x Fe_4-3x Sb _x O₆ solid solutions (0 x 0.154 and 0.923 x 1) of, respectively, hematite and bixbyite structure were identified.     

The reaction of benzothiazole sulfenamide with (TMS)3SiH: An example of degenerate-branched chain process

The reaction of sulfenamide 3 with (TMS)₃SiH initiated by the decomposition of AIBN at 76 °C has been studied in some detail. The reaction is a rare example of a radical chain-branching process. The two main products are dialkylamine 4 and the thiosilane 5. It is also established that 2-mercaptobenzothiazole (2) is formed in a substantial yield as one of the by-products. The mechanism of this chain autocatalytic reaction is complex due to a mix of different radical chain reactions and some discussion is provided. The amine obtained in a quantitative yield can arise from two independent routes of attack of (TMS)₃Si radical on sulfenamide 3. The minor route affords thiol 2 that can act as a catalyst for the major route during the reaction course and then gives a salt with secondary amine, which precipitates upon cooling. The origin of autocatalysis is discussed in some detail.     

A study on solvent extraction of Cu/II/ with 2-mercaptobenzothiazole into chloroform

A method has been developed for the rapid and selective extraction of Cu/II/ with 2-mercaptobenzothiazole /2-HMBT/ into chloroform. The effect of various parameters on the extractioncoefficient value have been studied. The stoichiometry of the extracted species of 12 /Cu2-HMBT/ was obtained by the slope ratio method and by the method of substoichiometric extraction.     

Mössbauer Spectroscopic Studies of K2SnCl6 and SnCl4·5H2O in Frozen Aqueous Solutions and in Ion Exchange Resins

Concentration dependence of isomer shift of K₂SnCl₆ and tin(IV) chloride was studied. Tin was hydrolyzed in both cation and anion exchange resins after water washing. Two pairs of these two solutions showing the same isomer shift values, and therefore the same , were selected for further studies in HCl solutions and in anion exchange resins. The first pair was 0.04 M K₂SnCl₆ and tin(IV) chloride solutions (δ=0.00 mm/s; =0): Their δ-[HCl] curves coincided each other. Tin was sorbed on anion exchange resin as pentachlorstannate(IV) at (HCl)≤6 N, and chiefly as hexachlorostannate(IV) at [HCl]≥7 N. The both complexes were sorbed when 6 N < [HCl] < 9 N. The δ-[HCl] curves of the second pair, 0.4 M K₂SnCl₆ and 3 M tin(IV) chloride(δ =0.23 mm/s; =3), also coincided each other, and tin was sorbed as pentachlorostannate(IV) from K₂SnCl₆ solutions in the HCl concentration range studied (≥5 N).     

Spinnability and rheological properties of sols derived from Si(OC2H5)4 and Zr(O-nC3H7)4 solutions

The shape of the polymers in the mixed alkoxide solutions of Si(OC₂H₅)₄ and Zr(n-OC₃H₇)₄ with various water contents (1, 2, 4, and 8 in molar ratio to alkoxide, r) and catalysts was examined by rheological measurements, and its relation with fiber drawing behavior of the solutions was described. It was found that fibers could be drawn in the viscosity range 1–100 P from the acid-catalyzed solutions with lower water contents of the molar ratio H₂O/alkoxide, r2. On the other hand, no fiber could be drawn from the acid-catalyzed solutions including a large amount of water (r4) and the base-catalyzed solutions.The relation between the intrinsic viscosity [] and the number average molecular weight M_n, namely []=KM _n ^a , has shown that the acid-catalyzed spinnable solutions (r=1 and 2) have linear polymers where the exponent a's are about 0.56 and 0.81, whereas non-spinnable solutions (r=4 and 8) have three dimensional network polymers or spherical particles where the exponent a's are 0.41–0.51 and 0.35.     

Synthesis, Formation Mechanism, and Crystal Structure of the Nitrosoruthenium(II) Nitrochloride Complex Fac-K2[RuNO(NO2)2Cl3]

Procedures for synthesis of the first nitrochloride complex of nitrosoruthenium(II), fac-K₂[RuNO(NO₂)₂Cl₃], are described and the mechanism of its formation is suggested. The compound was investigated by IR spectroscopy and X-ray phase and X-ray diffraction analyses. Crystal data for Cl₃N₃O₅K₂Ru: a = 7.050(1), b = 7.524(2), c = 10.125(2) , = 90.44(3), = 103.17(3), = 90.51(3)°, V = 522.9 ³, space group , Z = 2, d _calc = 2.589 g/cm³. The structure consists of the complex anions fac-[RuNO(NO₂)₂Cl₃]^2– and K⁺ cations. The complex crystallizes as triclinic plates and red orange prisms; it is well soluble in water, not readily soluble in KCl solutions, and insoluble in ethanol and acetone; the complex is stable when stored in air.     

Radiochemical separation of Ru/III/ with 2-mercaptobenzothiazole into chloroform employing solvent extraction technique

The reagent 2-mercaptobenzothiazole /2-HMBT/ has been used for the solvent extraction of Ru/III/. The extraction coefficient value of Ru/III/ has been evaluated, based on various parameters such as, effect of molarity of the acid, time of equilibration, time of heating, effect of various solvents and effect of various salts. The stoichiometry of the metal to reagent was determined by the method of substoichiometric extraction of slope-ratio method and was found to be 13. Separation factor and decontamination factor for various elements have also been studied.     

Acid-base properties of 1,2,5-oxadiazoles. 2. Aminofurazans

The behavior of 3-R-4-aminofurazans (R = NH₂, CH₃, OCH₃, N₃, COOH, and NO₂) in sulfuric acid solutions was studied by electronic and PMR spectroscopy. The constants of protonation (pK _aBH+) at the amino group and in the ring were calculated from the changes in the spectra. Dependences of the position of the absorption maxima corresponding to ^* transitions and the pK _aBH+ values and with the ^o substituent constants were found.See [1] for Communication 1.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 321–324, March, 1981.     

Über den Einbau von Fremdionen in γ-Al2O3, 2. Mitt.: Der Einfluß von Ca2+, Sr2+ und Ba2+ auf die thermische Beständigkeit von γ-Al2O3

Zusammenfassung Aluminiumhydroxidgele wurden aus Al-Nitratlösungen bei konstantem pH-Wert mittels NH₄OH gefällt, Ca, Sr und Ba-Ionen in Form ihrer Nitrate vor der Fällung zugesetzt und die Menge der in -Al₂O₃ eingebauten Fremdionen bestimmt. Diese ist bei konstantem pH-Wert von Menge und Art des vorgelegten Ions abhängig und wird von der Alterungszeit in Lösung nicht beeinflußt.Die thermische Stabilität des -Al₂O₃ wird durch den Einbau von Erdalkaliionen erhöht, wobei die für eine maximale Stabilisierung benötigte Fremdionenmenge mit steigendem Ionenradius abnimmt.Röntgenographische Untersuchungen zeigten, daß das Intensitätsverhältnis von Interferenzen bei reinen und erdalkalihältigen -Al₂O₃-Präparaten konstant bleibt, die Gesamtintensität der Reflexe bei erdalkalihältigen Präparaten jedoch geringer und die Linienbreite größer ist als bei reinem -Al₂O₃.

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Aluminium hydroxide gels have been prepared from aluminum nitrate solutions by precipitation with NH₄OH at constant pH. Ca-, Sr- and Ba-ions where added as nitrates prior to the precipitations, and the amount determined, which was incorporated in the -Al₂O₃. At constant pH-value incorporation is dependent on the amount and the kind of ion present, and independent of aging in solution.The thermal stability of -Al₂O₃ is enhanced by the presence of ions of alkaline earths. The amount of foreign ions necessary for maximum stabilisation decreases thereby with increasing ionic radius.Investigation of X-ray diffractions showed that the ratio of intensities of the interference remains constant with pure -Al₂O₃ and preparations containing alkaline earths, while the total intensity of the reflexes with alkaline earths decreases, and the width of the lines increases, compared with pure -Al₂O₃.

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MgF<Subscript>2</Subscript> films prepared from solvothermally treated precursor solutions

MgF₂ coating solutions were solvothermally treated at 160?°C for different time periods, this procedure induced crystallization and particle growth. Antireflection coatings prepared on glass from these solutions were compared to films derived from untreated precursor material. Ellipsometric porosimetry (EP) was employed to characterize structural features of coatings on glass as function of annealing temperature. Based on precursor solutions that had undergone solvothermal treatment antireflective coatings with a peak transparency exceeding 99% were prepared on PMMA substrates.

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Solvothermal treatment of MgF₂ precursor solutions results in crystallization of particles that can directly be applied to PMMA substrates for λ/4 antireflective films.

     

Mercaptobenzothiazole-functionalized magnetic carbon nanospheres of type Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript>@C for the preconcentration of nickel,copper and lead prior to their determination by ICP-MS

The authors describe double-shell magnetic nanoparticles functionalized with 2-mercaptobenzothiazole (MBT) to give nanospheres of the type MBT-Fe₃O₄@SiO₂@C). These are shown to be viable and acid-resistant adsorbents for magnetic separation of the heavy metal ions Ni(II), Cu(II) and Pb(II). MBT act as a binding reagent, and the carbon shell and the silica shell protect the magnetic core. Following 12 min incubation, the loaded nanospheres are magnetically separated, the ions are eluted with 2 M nitric acid and then determined by inductively coupled plasma-mass spectroscopy. The limits of detection of this method are 2, 82 and 103 ng L￣¹ for Ni(II), Cu(II), and Pb(II) ions, respectively, and the relative standard deviations (for n = 7) are 6, 7.8, and 7.4 %. The protocol is successfully applied to the quantitation of these ions in tap water and food samples (mint, cabbage, potato, peas). Recoveries from spiked water samples ranged from 97 to 100 %.

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Graphical abstract Mercaptobenzothiazole-functionalized magnetic carbon nanospheres of type Fe₃O₄@SiO₂@C were synthesized. Then applied for magnetic solid phase extraction of Ni(II), Cu(II) and Pb(II) from water and food samples with LOD of 0.002, 0.082 and 0.103 μg L^?1 respectively.

     

Solvent and substituent effects on the equilibrium between mononuclear and binuclear complexes of copper(II) carboxylates in 2-methylpyridine and 2,6-dimethylpyridine solutions

Electronic spectra of Cu(RCO₂)₂ [R=H, CH₃, CH₃CH₂, (CH₃)₂CH, C₆H₅, C₆H₅CH₂] as solutions in the pure amines, 2-methylpyridine, L, 2,6-dimethylpyridine, L, and in amine-chlorobenzene mixtures have been measured and interpreted in terms of the equilibrium 2Cu(RCO₂)₂L₂=Cu₂(RCO₂)₄L₂ +2L. Formation of the binuclear species was greater when 2,6-dimethylpyridine was the solvent. The measured equilibrium constants indicated that the tendency to form binuclear complexes in the solutions increased with increasing pK_a of the parent carboxylic acid.     

Formation of long-lived radicals in addition reactions to perfluoro-4-methyl-2-pentene

Conclusions The photolysis of liquid solutions of CF₃I and (CF₃)₂CFI in perfluoro-4-methyl-2-pentene at 240 run gives longlived radicals, which were identified as radical-adducts formed by the addition of CF₃ and (CF₃)₂CF radicals to the double bond of the perfluorolefin.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 184–185, January, 1989.     

Molecular structure, IR spectra of 2-mercaptobenzothiazole and 2-mercaptobenzoxazole by density functional theory and ab initio Hartree–Fock calculations

Quantum chemistry calculations have been performed using Gaussian03 program to compute optimized geometry, harmonic vibrational frequency along with intensities in IR and Raman spectra and atomic charges at RHF/6-31+G*, B3LYP/6-31+G* and B3LYP/6-31++G* levels for 2-mercaptobenzothiazole (MBT, C₇H₅NS₂) and 2-mercaptobenzoxazole (MBO, C₇H₅NOS) in the ground state. The scaled harmonic vibrational frequencies have been compared with experimental FT-IR and FT-Raman spectra. The results show that the scaled theoretical vibrational frequencies is very good agreement with the experimental values. A detailed interpretation of the infrared and Raman spectra of 2-mercaptobenzothiazole and 2-mercaptobenzoxazole was reported. Comparison of calculated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes.     

Room temperature synthesis and solid-state structure of Ni2P2O6·12H2O

The synthesis and crystal structure of Ni₂P₂O₆·12H₂O are reported. The compound was synthesized from aqueous solutions of nickel chloride and sodium hypodiphosphate at room temperature. The space group is orthorhombic, Pnnm. Unit cell dimensions are , , and , Z=4. The product is unstable with respect to dehydration above room temperature.