Preparation of alkali-metal hypothiophosphates in an alcoholic solution

A procedure was developed for preparation of lithium and sodium hypothiophosphates from the corresponding alkali-metal and phosphorus sulfides in ethanol. The possibility was explored for preparation of tin(II) hypothiophosphate in an alcoholic solution by an exchange reaction between sodium hypothiophosphate and tin(II) chloride.     

Direct spectrophotometric analysis of low level Pu(III) in Pu(IV) nitrate of Pu precipitation process feed solution

To achieve end user’s specified PuO₂, controlling and monitoring of Pu in its fourth valency state is essential prior to the conversion of Pu-nitrate to its oxide through oxalate precipitation process. Conventional radiometric procedure for the analysis of Pu oxidation state in Pu-nitrate solution containing trace level of Pu(III) has limitation due to oxidation of Pu(III) during the sample preparation with respect to acidity. A simple direct spectrophotometry using an optic fiber spectrophotometer was attempted for the estimation of trace level of Pu(III), after separating the bulk amount of Pu(IV) by maintaining the sample acidity. By using a synergistic mixture of 30 % TBP and 1 M theonyl trifluoro acetone in benzene, the Pu(IV) could be removed to a level which doesn’t interfere in the Pu(III) absorption.     

Preparation and characterization of nanostructured Ni(OH)2 and NiO thin films by a simple solution growth process

Nanostructured Ni(OH)2 thin films were prepared by a simple solution growth process with F(-) and NH3 used as Ni2+ coordination agents, and ammonia hydroxide solution used as OH(-) supplier to accelerate the hydrolyzation of nickel complex species. The results showed Ni(OH)2 thin films were constructed mainly with hexagonal beta-Ni(OH)2 nanorods; the F(-) and NH3 in reactive solutions played important roles in the film growth process; and solution pH had great influence on the morphologies of thin films, which was explained by the competition of Ni(OH)2 nucleation and growth in solutions. NiO crystallinity thin films were obtained by annealing Ni(OH)2 thin films at 400 degrees C for 2 h and the morphologies of the Ni(OH)2 thin films were sustained well during the annealed process.     

Semimicrodetermination of mercury(II) and zinc(II) by precipitation from homogeneous solution,using cation generation technique

An efficient semimicro gravimetric method for the determination of mercury(II) and zinc(II) is presented. Potassium thiocarbonate (PTC) has been used as a source of sulfide and thiocarbonate ions affording clean precipitation from homogeneous solution and allowing the direct weighing of the precipitate when dry. The use of EDTA, ammonium tartrate, and PTC for masking of adverse ions in alkaline medium has afforded an efficient analytical separation of Hg(II) and Zn(II). The mean relative error is less than 1% in these estimations.     

Formation of helical superstructures from a semi-fluorinated alkoxysilane through a surface and solution self-assembly process

Helical superstructures were obtained through a surface and solution self-assembly process when a semi-fluorinated alkoxysilane modified silicon wafer was immersed in water of pH values ranging from 5.0 to 7.0 for more than one month.     

Mechanism of sodium chloride diossolving in water and the process of the solution aging

By the method of Flicker Noise Spectroscopy (FNS) we studied the process of sodium chloride dissolving in water (3.5 wt %) at 294 K on the level of long-range order formation in liquid. It is established that the process of dissolving the salt includes the following steps: formation of instable colloid particles, instable solvate clusters of the salt ion pairs (iSCIP), instable dissolved polymers of globular type, and 12 h later beginning of a new process of formation stable solvate clusters of the salt ion pairs (sSCIP) and stable polymer globules on their basis. Stroke diagrams of the cluster nano-structure and a model of aging the salt solution are presented. Influence of atmospheric pressure on the SCIP average weight is demonstrated. It is concluded that on the SCIP surface there is a porous layer of solvate water with membrane properties. The cluster structure of the 3.5 wt % solution prepared by dissolving the salt is shown to differ from that of the solution obtained by dilution. The solutions long-range order is formed by the nano dispersion of the water solvated salt crystal nuclei. The mechanism of the solution aging is discussed.     

On the preparation of nanosized Al2(WO4)3 by a precipitation method

Nanosized aluminum tungstate, Al₂(WO₄)₃, is prepared by a precipitation reaction between Na₂WO₄ and Al(NO₃)₃. The structure of the precipitated composition is determined by powder XRD analysis, IR and ²⁷Al MAS NMR spectroscopy. The thermal properties are examined by DSC, DTA and TG analyses combined with gas evolved analysis. Particle sizes and morphology are examined by TEM analysis. Precipitation reaction leads to the formation of an amorphous composition, which consists of dimer and trimer aluminum hydroxide species and WO₄^2? groups. Finely dispersed particles with dimensions of about 25 nm are formed. The precipitated composition is decomposed to amorphous Al₂(WO₄)₃ immediately after H₂O release. At 630 °C, amorphous Al₂(WO₄)₃ crystallizes in an orthorhombic modification of Al₂(WO₄)₃, the enthalpy of crystallization being 58 kJ/mol. The nanosized particles remain intact after the crystallization of amorphous Al₂(WO₄)₃. A significant particle growth take places when nanosized Al₂(WO₄)₃ is heated from 600 to 800 °C.     

Modelling the separation by nanofiltration of a multi-ionic solution relevant to an industrial process

The current work focuses on the application of nanofiltration (NF) to the isolation of a pharmaceutical product, clavulanate (CA⁻), from clarified fermentation broths, which show a complex composition with five main identified ions (K⁺, Cl⁻, NH₄⁺, SO₄²⁻ and CA⁻). Our aim is to predict the rejection rates of these five ions, with the NF membrane Desal-DK, which may influence the separation of CA⁻ and play a role in the whole downstream process.     

Formation of an interlocked quadruplex dimer by d(GGGT)

A tetranucleotide sequence d(GGGT) has been shown to self-assemble into an interlocking quadruplex dimer. UV-melting studies indicated the existence of two species that each showed distinct quadruplex melting transitions, a low-T(m) species, Q(l), and a high-T(m) species, Q(h). Conditions were controlled to favor the formation of either Q(l) or Q(h). Q(l) and Q(h) each showed circular dichroism spectra characteristic of parallel quadruplexes. Negative ion nano-electrospray ionization mass spectrometry confirmed that Q(l) was a tetrameric complex, d(GGGT)(4), and Q(h) was an octameric complex, d(GGGT)(8). High-resolution (1)H NMR spectroscopy evidenced that d(GGGT)(4) was a C(4)-symmetric parallel tetramolecular quadruplex. The (1)H NMR spectrum of d(GGGT)(8) was consistent with a structure formed by the dimerization of a parallel, "slipped" tetramolecular quadruplex that has its diagonal strands staggered by one base. This "slippage" results in two guanine bases at the 5' end of the quadruplex being presented diagonally that are not involved in tetrads. Two such "slipped" quadruplexes dimerize via these free G-bases at the 5' ends by forming an extra G-tetrad. Each "slipped" quadruplex contributes two guanine bases to this extra G-tetrad. The formation of a novel GTGT tetrad is also observed at both the 3' ends of the interlocked quadruplex dimer.     

Epoxy resins (DGEBA): The curing and physical aging process

Differential scanning calorimetry (DSC) and infrared spectroscopy (IR) were used to monitor the degree of cure of partially cured epoxy resin (Epon 828/MDA) samples. The extent of cure, as determined by residual heat of reaction, concurred with that determined by monitoring the infrared radiation absorbance of the epoxide group near 916 cm^?l. The fictive temperature T_{f, g} was found to increase with the degree of cure, increasing rapidly during cure until reaching a value near the cure temperature T_c of 130°C (approximately 80% cure) where the material vitrified. The greatly reduced reaction rate during the final 20% of cure was not only a consequence of vitrification but, as revealed by infrared spectroscopy, the result of the depletion in the number of reactive epoxide groups. The endothermic peak areas and peak temperatures evident during the DSC scans were used as a measure of the extent of “physical aging” which took place during the cure of this resin, and after, fully cured samples were aged 37°C below their ultimate glass temperature for various periods of time. The rate of physical aging slowed as the temperature increment (T_t,g ? T_c) increased. Although an endothermic peak was evident after only 1 h of cure (T_{f, g} = 138.3°C), such a peak did not appear until fully cured samples were aged for 16 h or more. Enthalpy data revealed that for partially cured material, the fictive temperature T_{f, a}, reflecting physical aging, increased with curing time. In contrast, the T_{f, a}, for fully cured samples decreased with sub-T_g aging time. The characteristic jump in the heat capacity ΔC_p which occurred at the T_{f, g} decreased as curing progressed. This decrease appears to be dependent upon the rotational and vibrational degrees of freedom of the glass. Finally, a graphical method of determining the fictive temperature T_{f, a}, of partially and fully cured epoxy material from measured endothermic peak areas was developed.     

Formation of an oxo-free rhenium(v) complex with 2-aminothiophenol

The reaction of a twofold molar excess of 2-aminothiophenol (H₂L) with trans-[ReOCl₃(PPh₃)₂] in benzene led to the isolation of the oxo-free rhenium(V) complex [ReCl(PPh₃)L₂] (1). IR, ¹H NMR and X-ray crystallographic results indicate that the ligands L coordinate in a dianionic amidothiolate form to the metal and that the complex has the unusual skew-trapezoidal bipyramidal geometry. The ligands L have an average bite angle of 78.8(1)°, with average Re–N and Re–S bond lengths equal to 1.978(5) and 2.297(1)?Å, respectively.     

Isolation of an oxomanganese(V) porphyrin intermediate in the reaction of a manganese(III) porphyrin complex and H2O2 in aqueous solution

The reaction of [Mn(TF(4)TMAP)](CF(3)SO(3))(5) (TF(4)TMAP=meso-tetrakis(2,3,5,6-tetrafluoro-N,N,N-trimethyl-4-aniliniumyl)porphinato dianion) with H(2)O(2) (2 equiv) at pH 10.5 and 0 degrees C yielded an oxomanganese(V) porphyrin complex 1 in aqueous solution, whereas an oxomanganese(IV) porphyrin complex 2 was generated in the reactions of tert-alkyl hydroperoxides such as tert-butyl hydroperoxide and 2-methyl-1-phenyl-2-propyl hydroperoxide. Complex 1 was capable of epoxidizing olefins and exchanging its oxygen with H(2) (18)O, whereas 2 did not epoxidize olefins. From the reactions of [Mn(TF(4)TMAP)](5+) with various oxidants in the pH range 3-11, the O-O bond cleavage of hydroperoxides was found to be sensitive to the hydroperoxide substituent and the pH of the reaction solution. Whereas the O-O bond of hydroperoxides containing an electron-donating tert-alkyl group is cleaved homolytically, an electron-withdrawing substituent such as an acyl group in m-chloroperoxybenzoic acid (m-CPBA) facilitates O-O bond heterolysis. The mechanism of the O-O bond cleavage of H(2)O(2) depends on the pH of the reaction solution: O-O bond homolysis prevails at low pH and O-O bond heterolysis becomes a predominant pathway at high pH. The effect of pH on (18)O incorporation from H(2) (18)O into oxygenated products was examined over a wide pH range, by carrying out the epoxidation of carbamazepine (CBZ) with [Mn(TF(4)TMAP)](5+) and KHSO(5) in buffered H(2) (18)O solutions. A high proportion of (18)O was incorporated into the CBZ-10,11-oxide product at all pH values but this proportion was not affected significantly by the pH of the reaction solution.     

Hydrolytic precipitation reaction of titanium(IV) from (Na,H)Cl aqueous solution

The hydrolytic precipitation of titanium(IV) in 2.0 mol dm⁻³ (Na, H)Cl aqueous solution at 25.0°C has been studied by measuring the free hydrogen ion concentration by a potentiometric method and the aqueous concentration of titanium(IV) by a spectrophotometric method. Under conditions where the solution is saturated with regard to precipitated titanyl(IV) hydroxide, monomeric and polycationic species, such as, TiO²⁺, TiO(OH)₂, and [(TiO)₈(OH)₁₂]⁴⁺, were deduced as being present in the solution. A scheme for the hydrolytic precipitation equilibria has been deduced.     

Formation constants of copper(I)-olefin complexes in aqueous solution

A simple kinetic method has been applied to measure the formation constants of aqueous copper(I) with fumaronitrile, dimethyl fumarate, and fumaric and maleic acids. At 0.14 M ionic strength, the values of beta(1) are (0.85 +/- 0.02) x 10(3), (6.1 +/- 0.1) x 10(3), (7.3 +/- 0.1) x 10(3), and (2.2 +/- 0.4) x 10(3) M(-1), respectively. The values for the last two olefins are compared to previous results. Values of beta(1) for hydrogen maleate and beta(2) for fumaronitrile also have been determined. A reanalysis of much earlier work has been done, and all the results are discussed in terms of the effect of substituents on the olefin on the beta(1) values. The structure of bis(fumaronitrile)copper(I) nitrate also is reported. The nitrile is N-coordinated to copper(I), which has a distorted tetrahedral geometry, while the overall structure consists of macrocyclic Cu(6)(fumaronitrile)(6) rings which extend in three dimensions.