A study of corrosion on a rotating iron disk electrode

Corrosion of iron in slightly acidified sodium sulphate solutions (mainly pH 4.5) in the open air was studied with a rotating disk electrode method at room temperature.Microscopic observations of corroded iron disk surfaces in the pH 4.5 solution revealed that iron initially corrodes locally with the formation of round pits of 10–30 μm in diameter and of(0.6–1.3) × 10³ in number per apparent square centimetre followed by the U-shaped brown protective wall formation of precipitates (rust) outside the pits. Each protective wall is formed along the lines of flow of the solution adjacent to the iron surface and each pit is located near the upstream end of the wall. Steady state of corrosion sets in when the parts of surface area surrounded by the wall are completely covered with a microscopically non-porous rust film.The amount of iron in the rust film and the total amount of corrosion of iron including that in the film increase parabolically with the increase in the time of immersion. The amount of iron in the film increases in proportion to the total amount of corrosion independently of the speed of rotation of the disk electrode even in the steady state.The fraction of area of iron surface not covered with the film decreases with time and reaches a certain fixed value in the steady state: the value is smaller at higher rotational speed. The corrosion rate is proportional to the uncovered area, as the corrosion is near the steady state. The pH of the bulk solution increases as corrosion progresses.The corrosion rate of iron can be well interpreted by assuming that the rate is controlled by the diffusion of oxygen from the bulk solution to the surface of iron and that the rust film on iron impedes the diffusion of oxygen.     

The nephritogenic glycopeptide from rat glomerular basement membrane. X. Synthesis of an N-triglycosyl dipeptide and characteristics of its cis-trans isomers.

Isomers of O-alpha-D-glucopyranosyl-(1----6)-O-beta-D-glucopyranosyl- (1----6)-N-[L-aspart-1-oyl-(L-proline)-4-oyl]-alpha-D-glucopyranos ylamine have been prepared, as models for a derivative possibly present in the glomerular basement membrane of rats, by condensation of the corresponding dipeptide derivative (5) with triglycosylamine (4) in the presence of O,O-diethylcyanophosphonate, followed by deprotection of the trisaccharide-dipeptide derivative. During the deprotection process, cis- and trans-isomers containing proline were separated by silica gel column chromatography and also reversed-phase high performance liquid chromatography.     

Vibrational energies for the X1A1, A1B1, and B1A1 states of SiH2/SiD2 and related transition probabilities based on global potential energy surfaces

Transition probabilities were evaluated for the X(1)A(1)-A(1)B(1) and A(1)B(1)-B(1)A(1) systems of SiH(2) and SiD(2) to analyze the X-->A-->B photoexcitation. The Franck-Condon factors (FCFs) and Einstein's B coefficients were computed by quantum vibrational calculations using the three-dimensional potential energy surfaces (PESs) of the SiH(2)(X(1)A(1),A(1)B(1),B(1)A(1)) electronic states and the electronic transition moments for the X-A, X-B, and A-B system. The global PESs were determined by the multireference configuration interaction calculations with the Davidson correction and the interpolant moving least-squares method combined with the Shepard interpolation. The obtained FCFs for the X-A and A-B systems exhibit that the bending mode is strongly enhanced in the excitation since the equilibrium bond angle greatly varies with the three states; the barrier to linearity is evaluated to be 21,900 cm(-1) for the X state, 6400 cm(-1) for the A state, and 230-240 cm(-1) for the B state. The theoretical lifetimes for the pure bending levels of the A and B states were calculated from the fluorescence decay rates for the A-X, B-A, and B-X emissions.     

Syntheses of 3-substituted furans via lithium di(3-furyl)cuprate—the application of lithium di(3-furyl)cuprate to the total synthesis of dendrolasin

One step syntheses of 3-substituted furans by the reactions of a new reagent, lithium di(3-furyl)cuprate $\text{1}$, with various substrates and the application of $\text{1}$ to a total synthesis of dendrolasin are described.     

Synthesis and γ-radiolysis of 2′-deoxy-5-fluorouridine and 5-fluorouridine derivatives

Seventeen compounds having a variety of substituents at the 3- and 5′-positions of 2′-deoxy-5-fluorouridine (5-FUdR) and 5-fluorouridine (5-FUR) were synthesized, and their γ-radiolysis in aqueous solutions were studied. The compounds having thioureido (RNHCSNH, R ? H, PhCH₂, acyl) and thiocarbonylamino (XCSNH, X ? PhCH₂S, PhO) groups at the 3-position of 5-FUdR were efficiently cleaved to give 5-FUdR with high G values upon γ-irradiation of their aqueous solutions. The active species for these cleavage reactions were hydrated electron (e^? _aq), H^? and HO^?. However, the compounds having a dimethylsulfoxyimino group at 3-position of 5-FUdR and 5-FUR afforded 5-FUdR and 5-FUR only under the radiolysis conditions where e^? _aq becomes a principal active species. The compound having a 2-benzoylthiazoylthiocarbonylamino group at the 3-position of 5-FUdR showed the highest reactivity toward HO^.. The mechanisms of these γ-radiolysis reactions are discussed. The examination of anticellular activities of γ-irradiated compounds having a thiocarbonylamino group at the 3-position of 5-FUdR toward murine Sarcoma 180 cells revealed that these compounds may be utilized as a candidate for a radiation-induced drug (RID).     

Some vanadium(V) complexes as reagents for the photometric determination of alcohols

Vanadiuin(V) com: with an acidic hydroxy group attached to the metal form the crorrresponding.; with alcohols. These esters show a characteristic absorption at 445–480 that alcoholic hydroxy groups can be determined photometrically. The formation constant of the n-butanol esters of vanadium maltolate and 2-methyl-.S-hydroxyquinolinate Were determined in benzene or benzenechloroform (1:1). Simple methods are determined for the determination of alcohol in the concentration range 10^-1–10^-4M.     

Selective Formation of Spinel Iron Oxide in Thin Films by Complexing Agent-Assisted Sol-Gel Processing

The structure of iron oxide was controlled by regulating the hydrolytic polymerization of aquo iron complexes with organic polydentate ligands such as diols. Iron oxides were prepared by calcining the precursor polymers obtained from iron nitrate nonahydrate and diols. When the diols were 1,2-pentanediol, 1,2-hexanediol and 1,2-octanediol, α-Fe₂O₃ with corundum structure appeared exclusively or as the main crystalline phase, in spite of the amount of diol used and the calcination temperature. In the case of 1,2-decanediol and 1,2-dodecanediol, when five moles of the diols were used to one mole of iron nitrate and the calcination temperatures were below 400°C, ψ-Fe₂O₃ with spinel structure appeared as the main phase and, when less than five moles of the diols were used, α-Fe₂O₃ appeared exclusively or as the main phase, irrespective of the calcination temperature. This tendency was also observed in thin films. Thus, a transparent magnetic film composed of γ-Fe₂O₃ could be prepared by applying a benzene solution of the iron polymer, obtained with 5 equivalents of 1,2-decanediol, on quartz and calcining the gel film at 350°C.     

A novel oligothiophene derivative as a hole‐transport with emitting material for OLED

A novel oligothiophene derivative containing the triphenylamine moiety with high glass transition temperature (T_g; 135 °C), 5,5′‐{bis[4‐di(4‐thiophenyl)amino]phenyl}‐2,2′‐bithiophene (TTPA‐dimer) was synthesized by the dimerization of tris[4‐(2‐thienyl)phenyl]amine (TTPA) with a palladium catalysis. Some types of electroluminescent (EL) devices that use the amorphous material for a hole‐ and an electron‐transporting with an emitting layer were fabricated. These devices emitted a bright green‐yellowish light (λ_emi; around 510 nm) with a small full width at half maximum (FWHM) rather than that of Alq₃. The single layer EL device showed a maximum luminance of 221 cd/m² at 8 V (0.06 lm/W at 100 cd/m²). On the other hand, the double layer (TTPA‐dimer/Alq₃) EL device that used Alq₃ as the electron transport material was increased up to 10830 cd/m² at 12 V (0.89 lm/W at 300 cd/m²) and with a lower turn‐on voltage (3.2 V at 0.1 cd/m²) than other types of EL devices. Copyright © 2003 John Wiley & Sons, Ltd.     

A free energy calculation study of the effect of H-->F substitution on binding affinity in ligand-antibody interactions

Changes in binding affinity to catalytic antibody 6D9 of chloramphenicol phosphonate derivatives (CPDs) containing H or F were investigated by performing free energy calculations based on molecular dynamics simulations. We calculated the binding free energy, enthalpy, and entropy changes (DeltaDeltaG, DeltaDeltaH, and -TDeltaDeltaS) attributable to H-->F substitution by comparing results for CPDs containing a trifluoroacetylamino group (CPD-F) or an acetylamino group (CPD-H). The calculated DeltaDeltaG, DeltaDeltaH, and -TDeltaDeltaS values were -2.9, -6.3, and 3.5 kcal mol(-1) and close to experimental values observed for a series of similar ligands, chloramphenicol phosphonates with F and H (-1.4, -3.5, and 2.1 kcal mol(-1)). Therefore, CPD-F binds more strongly to 6D9 than does CPD-H. To clarify the origin of the large difference in DeltaDeltaG, we apportioned the calculated values of DeltaDeltaG and DeltaG for the associated and dissociated states into contributions from various atomic interactions. We found that the H-->F substitution increased the binding affinity mainly by decreasing the hydration free energy and not by increasing favorable interactions with the antibody. The decreased hydration free energy of the ligand was mainly due to unfavorable coulombic interactions between the trifluoroacetylamino group and solvent waters, which increased the free energy of the dissociated state (by about 3.7 kcal mol(-1)). Also, the trifluoroacetylamino group slightly increased the free energy level of the associated state (about 0.8 kcal mol(-1)) because favorable van der Waals interactions compensated for unfavorable coulombic interactions with antibody atoms. In addition, the enthalpy and entropy changes, DeltaDeltaH and -TDeltaDeltaS (computationally -6.3 and 3.5 kcal mol(-1)), originated mainly from a decrease in hydration free energy in the dissociated state. The CPD-F and CPD-H ligands had substantially different structures in the dissociated and complexed states.