Ion—Molecule reactions of environmentally significant organotin compounds in a triple quadrupole mass spectrometer system

Tandem MS techniques have been used to examine the formation of cluster ions derived from organotin compounds of environmental significance. The cluster formation was based on the addition of either water or methanol molecules (common HPLC solvents) to a cationic species derived from the organotin compound. For the compounds and conditions studied, cluster adducts were only observed from trisubstituted tin cations. The results show that, in high-pressure ionization methods used in the interface between HPLC and MS, the tin atom may be associated with a range of ions depending on the system parameters, and that care should be taken if selection ion monitoring (SIM) is to be used.     

超声波作用下天然气水合物的形成

实验搭建了一套高压条件下超声波作用于天然气水合物反应的装置系统，该系统中超声波的频率为20kHz，功率为0-150W可调。利用该装置研究了超声波对天然气水合物生成过程和引导时间的影响。实验发现声场中生成特征曲线诸如温度、压力、流量等随着时间的推迟与静态反应时不同，反应引导时间约缩短至静态时的1／6，分解后重新反应引导时间甚至缩短至静态的1／10。水合物成核速率提高是由于超声波提高了传质系数、成核点浓度和过饱和度，而降低了界面能。     

Spectrophotometric determination of micro amounts of tetrathionate via its oxidation with permanganate

The reaction conditions of tetrathionate with permanganate were investigated by varying reaction time, temperature and amounts of sulphuric acid and permanganate. Under the optimal conditions for the reaction of tetrathionate with permanganate, both penta- and hexathionate were also oxidised; each one mol of polythionates (S _x O ₆ ^2– x=4, 5 and 6) reacts with (x–1.5) mol of permanganate. The proposed method is based on the reaction of tetrathionate with a given excess amount of permanganate in a sulphuric acid medium and on the spectrophotometric measurement of the iodine as triiodide formed by the oxidation of iodide with the excess of permanganate. This method could be successfully applied to the determinations of tetrathionate (4 × 10^–7 to 2 × 10^–5 M), pentathionate (3 × 10^–7 to 1.43 × 10^–5 M) and hexathionate (2 × 10^–7 to 1.11 × 10^–5 M), and gave a higher sensitivity than any previous methods without solvent extraction.     

A prepared pattern with wavelength selection in directional solidification

As crystal growth is a vital link in the long chain of processes leading to state-of-the-art technological devices, a great deal is known about patterns formed at the solid-liquid interface of a growing crystal. However, some basic questions are still unanswered concerning macroscopic features exhibited by a moving solid-liquid interface. Even for the first instability, the cellular instability, a unique steady-state wavelength does not emerge from theory. Furthermore, while wavelength selection is observed in many different materials, its origin is still to be discovered. By breaking continuous rotational symmetry of the flat solid-liquid interface about the pulling direction v, we prepared a cellular pattern with a well-defined wavelength by front propagation into the unstable uniform state. The material is succinonitrile and the rectangular interface geometry is formed by loading it into a flat capillary. The capillaries are chosen to provide a sample thicknessy ₀ = 100n , and width 10y ₀ and 20y ₀. We use a high-resolution directional solidification apparatus and grow the crystal from grain-boundary-free seed crystals. Surprisingly, the shape of the groove next to the uniform state is initially well-described by nearly self-similar Gaussians. This suggests that the initial perturbation of the interface is localized to a region /2 around a groove. A pattern with a well-defined wavelength is established when the half-width of the Gaussians ₀16m is small compared to 80m so there is little overlap between a groove and its predecessor or successor. When overlap is significant, the pattern is time-dependent. These results suggest that wavelength selection in this prepared pattern is a consequence of front propagation of a localized perturbation.     

Wire-Arc Spray Modeling

A model is presented describing the details of the wire-arc spray process. The model consists of several submodels each treating a different part of the process. A compressible flow model describes the supersonic nozzle flow upstream of the wire tips. The arc is described by a 3-D arc in cross-flow model using different boundary conditions for the cathode and the anode boundary. The resulting temperature and velocity contours serve as upstream boundary for a 2-D turbulent jet model. Particle generation and acceleration is described by treating the initial droplet formation for the anode and the cathode wire separately and then using the resulting particle size and velocity distributions in a secondary break-up model. Comparison with some experimental results show acceptable agreement. This modeling approach may be used for optimization of wire-arc spray equipment.     

Enthalpie De Formation Et De Melange De Phosphoapatites Calco-Cadmiees Chlorees

Calcium–cadmium chlorapatites solid solutions with the general formula Ca_10–xCd_x(PO₄)₆Cl₂,1≤x≤10, were prepared by solid state reaction and characterized by X-ray diffraction, infrared spectroscopy and chemical analysis. Using an isoperibol calorimeter, their enthalpies of solution in 9 mass% nitric acid were measured. In order to determine the enthalpies of formation and enthalpies of mixing, thermochemical cycles were proposed and complementary experiences were performed. The results obtained show a decrease of the enthalpy of formation with the amount of cadmium introduced in the lattice. The variation of mixing enthalpy vs. x=Cd/(Cd+Ca) shows a maximum at about x=0,4. This could be explained by the existence of two cationic sites in the phosphoapatite structure. This revised version was published online in August 2006 with corrections to the Cover Date.     

The properties and potential uses of cyclodextrin derivatives

The hydroxyl groups can be selectively substituted to control the solubility and the complex forming selectivity of the modified cyclodextrins (CDs). Among the methylated CDs only two well-defined compounds can be taken into consideration: dimethyl- and dimethyl-CD (DIMEB and TRIMEB). In an aqueous solution of DIMEB the solubility of rather insoluble compounds and drugs like steroids, vitamin D₃, lidocaine and hydrocortisone increases. In some cases their stability and bioavailability are also improved. On the other hand, the hydrolysis rate of carmofur, coumarins etc. is retarded by the methylated cyclodextrins with blocked hydroxyl groups. The drug solubilizing capacity of hydroxypropyl-CD (HPBCD) is in most cases lower than that of DIMEB. The degree of substitution (DS) shows no remarkable effect on the solubilizing properties of HPBCD in the case of indomethacin, Dipiridamole etc., but in the case of Tolnaftate the solubility was enhanced by increasing the DS, other examples are shown.     

1,1-Insertion of substituted alkynes into the Ir-O bond of η-carboxylato iridium complexes

Alkyl-carbonyl-iridium [Ir(CH₃)(CO)(η²-O₂CR′)(PPh₃)₂]⁺ (1, R′ = CH₃, Ph, p-C₆H₄CH₃) react with alkynes (RCCH; R = Ph, p-C₆H₄CH₃) in the presence of NEt₃ to give acyl-alkynyl-iridium Ir(C(O)CH₃)(-CCR)(η²-O₂CR′)(PPh₃)₂ (4) which further react with RCCH to give alkyl-carbonyl-cis-bis(alkynyl) iridium Ir(CH₃)(CO)(CCR)₂(PPh₃)₂ (5). cis-Bis(alkenyl)iridium complexes, Ir(-CHCH₂)₂(η²-O₂CCH₃)(PPh₃)₂ (6) and (η²-O₂CCH₃)(PPh₃)₂ (7) react with substituted alkynes RCCH (R = Ph, p-C₆H₄CH₃, cyclohex-1-enyl) to give cis-bis(alkynyl) Ir(CCR)₂(η²-O₂CCH₃)(PPh₃)₂ (9) that further react with RCCH to undergo the alkyne insertion reaction into the Ir-O bond to produce iridacycles containing vinyl acetate ligands, (-CCR)₂(PPh₃)₂ (8).     

Synthesis and complexing properties ofcis,cis-1,3,5-tri-[2-(diphenylphosphinyI)ethylamino]cyclohexane

A novel polydentate phosphorus-containing complexing agent,cis,cis-1,3,5-tri[2-(diphenyl-phosphinyl)ethylamino]cyclohexane, has been prepared on the basis ofcis,cis-1,3,5-triamino-cyclohexane. The method of potentiometric titration in an aqueous—organic medium (70% ethanol, ionic strength 0.01M LiNO₃, 298 K) has been used to study the acid-base and complexing properties of the title compound. The ligand thus prepared forms 11 complexes with Cu²⁺, Co²⁺, Zn²⁺, and Ni²⁺ cations; formation of hydroxocomplexes MOHL⁺ has been observed in the case of Zn²⁺ and Cd²⁺.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1276–1279, July, 1993.The authors are grateful to A. G. Matveeva for his assistante in discussing the results of this study and in preparing this paper.