Flow injection determinations of polyphosphates based on colored metal complexes of xylenol orange and methylthymol blue

Substitution reactions between samples and colored metal complexes, such as magnesium-methylthymol blue and cerium(III)-xylenol orange, are applied to flow injection determinations of orthophosphate, diphosphate, triphosphate and EDTA. Various types of manifold with a stopped-flow device are used; the importance of addition of reagents in a logical sequence is stressed. Kinetic and thermodynamic factors associated with the substitution reactions were found to be significantly reflected in the f.i.a. profiles and stopped-flow signals. The working ranges of the methods are 10^-5–10^-4 M.     

Soft X-ray emission study of thermally treated Ni(film)/4H–SiC(substrate) interface

Deposition of Ni as contact on 4H–SiC has been investigated. Ni/4H–SiC samples were annealed at temperatures of 600, 800 and 950 °C for 30 min and were non-destructively characterized by soft X-ray emission spectroscopy (SXES) using synchrotron radiation as excitation. Si L_2,3 SXE showed the formation of Ni₂Si for all annealing temperatures. The C K SXE indicated the formation of graphite and graphitic carbons at annealing temperatures of 950 °C and below 800 °C, respectively.     

Polymerization of coordinated monomers. XX. Ab initio molecular orbital study on the binary molecular complex composed of methyl methacrylate and boron trichloride

The stereo and the electronic structures of methyl methacrylate and the binary molecular complex composed of methyl methacrylate and boron trichloride are determined by quantum chemical calculations based on ab initio molecular orbital methods with the STO-3G basis set. The Stable structures of methyl methacrylate in the free state are a transoid from and a cisoid form. The transoid form is slightly (0.5 kcal/mol) more stable than the cisoid form. The total energy change accompanying binary molecular complex formation is calculated to be ?43 kcal/mol. The most stable structure of the binary molecular complex composed of methyl methacrylate and boron trichloride is a twisted form in which the dihedral angle between the vinyl group and the ester group is 19.7°. A large amount of electron transfer from methyl methacrylate to boron trichloride is calculated to occur on binary molecular complex formation. Mulliken's population analysis shows the electron transfer to be the origin of the twist of the binary molecular complex. The energy level of the lowest unoccupied molecular orbital is substantially lowered by the coordination of boron trichloride.     

Decomposition of chlorofluorocarbons and hydrofluorocarbons in water by ultrasonic irradiation

The sonochemical degradation of CFC-113 (F₂ClC---CCl₂F), HCFC-225ca (F₃C---CF₂CCl₂H), HCFC-225cb (F₂ClC---CF₂---CClFH) and HFC-134a (F₃C---CF₂H) in water was investigated. The decomposition rates of CFC-113 increased with increasing the concentration of the CFC and at high concentration the rates far exceeded the rate of OH radical formation by water sonolysis, and OH radicals seemed to have little effect on the decomposition. The pyrolysis in the cavitation bubbles was suggested.     

Flow injection analysis of inorganic polyphosphates

Flow injection analysis is applied to the determination of orthophosphate and polyphosphates, such as diphosphate and triphosphate. A strongly acidic solution containing molybdenum(V) and molybdenum(VI) is used as the carrier so that hydrolysis of polyphosphates and color development of the resultant orthophosphate can be achieved simultaneously. For complete chemical reaction, the temperature of the reaction coil is maintained at 140° C. Application of a back-pressure coil is then necessary to eliminate the noise caused by gas bubbles. Total amounts of inorganic polyphosphates can be determined at a sampling rate of 45 samples per hour with a relative standard deviation of less than 1%. In addition, the flow injection system is shown to be useful as a post-column detector for high-performance liquid chromatography of inorganic polyphosphates. The efficiency of this system is compared with that of an air-segmented flow system.     

From penicillin to penem and carbapenem. III C1-unit introduction at C-4 position of azetidinone

Monocyclic β-lactams ($\text{1}$) were converted into 4-cyano derivative $\text{2}$ (C₁-unit introduction) under two phase reaction conditions. The cyano group in $\text{2}$ was successively transformed into $\text{3}$ and $\text{4}$, which are thought to be important precursors for the carbapenem synthesis.     

Effect of Br− ions on the F-center formation in KCl crystals under u.v. light irradiation

The relative efficiency of the F-center formation, Y_F in KCl crystals has been studied as a function of photon energy of u.v. light between 5.7 and 10.0 eV. Y_F is maximum at the peak of the absorption band due to the localized excitons at Br^? ions, and increases with Br^? concentration. Results suggest an important role of the localized excitons in the F-center formation.     

Simultaneous measurement of temperature and velocity maps by inversion recovery tagging method

A new method, called the inversion recovery (IR) tagging method, for simultaneous measurement of temperature and velocity maps of flowing fluid has been developed. The present method employs a set of tagging pulses which acts as an inversion pulse of the conventional IR method, based on the temperature dependence of the spin-lattice relaxation of water proton in a fluid, and has the advantage of being able to compensate the reduction of the NMR signal intensity due to flow motion and to reduce the total time to measure these maps. First, the accuracy of the temperature measurement of stagnant doped water in a differentially heated cell using the conventional IR method, as the basic sequence of the IR tagging method, has been evaluated. The accuracy was within 10% of the temperature difference DeltaT = 17.2 degrees C and the measurable temperature resolution was within +/-0.5 degrees C. Then temperature and velocity maps of the flowing doped-water through a cooled pipe were measured simultaneously by the IR tagging method, and the accuracy of temperature measurement was evaluated. The accuracy obtained using the present method was within 15% of the temperature difference DeltaT = 15 degrees C.     

Structural study of Si(1 1 1)-6 × 1-Ag surface using surface X-ray diffraction

The surface structure of Si(1 1 1)-6 × 1-Ag was investigated using surface X-ray diffraction techniques. By analyzing the CTR scattering intensities along 00 rod, the positions of the Ag and reconstructed Si atoms perpendicular to the surface were determined. The results agreed well with the HCC model proposed for a 3 × 1 structure induced by alkali-metals on a Si(1 1 1) substrate. The heights of the surface Ag and Si atoms did not move when the surface structure changed from Si(1 1 1)-√3 × √3-Ag to Si(1 1 1)-6 × 1-Ag by the desorption of the Ag atoms. From the GIXD measurement, the in-plane arrangement of the surface Ag atoms was determined. The results indicate that the Ag atoms move large distances at the phase transition between the 6 × 1 and 3 × 1 structures.