Temperature dependence of oxygen reduction activity at Pt-Fe, Pt-Co, and Pt-Ni alloy electrodes

Oxygen reduction reaction (ORR) activity and H(2)O(2) formation at Pt(54)Fe(46), Pt(68)Co(32), and Pt(63)Ni(37) electrodes in 0.1 M HClO(4) solution at 20 to 90 degrees C were investigated by using a channel flow double electrode method. In the temperature range of 20-50 degrees C, the apparent rate constants k(app) for ORR at these electrodes were found to be 2.4-4.0 times larger than that at a pure Pt electrode, whereas their apparent activation energies of 41 kJ mol(-1) at -0.525 V vs E degrees (0.760 V vs RHE at 30 degrees C) were comparable to that at the Pt electrode. H(2)O(2) yield was ca. 1.0% at Pt(54)Fe(46) and ca. 0.16% at Pt(68)Co(32) and Pt(63)Ni(37) between 0.3 and 1.0 V vs RHE. The k(app) values at the alloy electrodes decreased with elevating temperature above 60 degrees C, and settled to almost the same values at the Pt electrode. The H(2)O(2) production was not detected at the alloy electrodes once heated at the high temperature in the solution, probably due to the thickening of the Pt skin-layer by a considerable dissolution of nonprecious metal components (Fe, Co, Ni) from the alloys.     

Reaction of azulenes with 1-trifluoromethanesulfonylpyridinium trifluoromethanesulfonate (TPT) and synthesis of the parent azulene

2-Azulenyl trifluoromethanesulfonate was prepared by the reaction of 2-hydroxyazulene with trifluoromethanesulfonic anhydride in the presence of triethylamine as a base. Under the use of pyridine, 1-trifluoromethanesulfonylpyridinium trifluoromethanesulfonate further reacted with 2-azulenyl trifluoromethanesulfonate to give 1-(1-trifluoromethanesulfonyl-1,4-dihydropyridin-4-yl)azulenyl trifluoromethanesulfonate. Moreover, we found that azulenes also reacted with 1-trifluoromethanesulfonylpyridinium trifluoromethanesulfonate to give 4-(1-azulenyl)-1,4-dihydropyridine derivatives and 6-(1-azulenyl)-1-trifluoromethanesulfonyl-1-aza-hexa-1,3,5-triene depending on the reaction conditions. 2-Azulenyl trifluoromethanesulfonate was converted finally into the parent azulene in excellent yield by palladium-catalyzed reduction using formic acid as a reducing reagent.     

Internal conversion study on the contact charge density of57Fe impurity atoms in Au metal

Three different internal conversion spectra were measured on the 14.4 keV transition of⁵⁷Fe in Au metals. Adaptability of our method for analysing the line intensity, i.e. the deconvolution-reconvolution method with the constant tail fraction rule was tested experimentally. The obtained 4s electron densities, 4_s(o), of Fe impurity atoms in Au agreed on four samples within the error. The weighted mean value of 4_s(o) of Fe in Au is 4.98±0.68a ₀ ^–3 . It is concluded that the method of analysis is reasonable in this type of experiment.     

Photoisomerization and thermal reversion of [3.3] (1,4)naphthaleno (9,10) anthracenophane derivatives

All compounds (I and II) photoisomerized to III and IV with φ=0.3 both in air and nitrogen while thermal reversion of III was 40 times slower than that of IV indicative of strained structure of I as judged by UV and NMR spectroscopy.     

Reactions of carbon cluster ions stored in an RF trap

Reactions of carbon clusterions with O₂ were studied by using an RF ion trap in which cluster ions of specific size produced by laser ablation could be stored selectively. Reaction rate constants for positive and negative carbon cluster ions were estimated. In the case of the positive cluster ions, these were consistent with the previous experimental results using FTMS. Negative carbon cluster ions C _n ^– (n=4–8) were much less reactive than positive cluster ions. The C_nO^– products were seen only in n=4 and 6.     

Synthesis of amphiphilic particles in the presence of inert solvents and their application to lipase immobilization

To develop monodisperse amphiphilic polymer particles on which a large amount of lipase could be immobilized, we performed seed polymerizations of glycidyl methacrylate and allyl methacrylate in the presence of nonpolar inert and polar inert solvents. The amphiphilic porous polymer particles, which had both hydrophilic guanidino groups and hydrophobic stearoyl groups, were synthesized in the presence of n‐decane and had a large amount of macropores with diameters of 50–1000 nm. The amount of lipase immobilized on the amphiphilic particles synthesized in the presence of n‐decane was 3.85 times that of the lipase immobilized on the amphiphilic particles synthesized in the absence of a solvent. The immobilized lipase prepared with the amphiphilic particles synthesized in the presence of n‐decane exhibited a high transesterification activity in n‐hexane and could be used repeatedly without a considerable activity loss. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 874–884, 2002; DOI 10.1002/pola.10178     

Chemiluminescent decomposition of a dioxetane bearing a 3-(1-cyanoethenyl)phenyl moiety induced by Michael addition of an anion of malonate

A thermally stable dioxetane bearing a 3-(1-cyanoethenyl)phenyl group (1) was synthesized. Michael addition of an anion of malonate (3a,b) to a dioxetane (1) substituted with a 3-(1-cyanoethenyl)phenyl moiety took place to give an intermediary dioxetane bearing a benzylic anion, which decomposes rapidly with accompanying emission of crimson light. When an anion of chloromalonate (3c) was used as a base, intramolecular cyclopropanation of 3c occurred concurrently with the Michael-addition-induced chemiluminescent decomposition.     

Ruthenium complex-catalyzed allylic alkylation of carbonucleophiles with allylic carbonates

Allylic carbonates except for allyl methyl carbonate reacted with carbonucleophiles such as ethyl acetoacetate in the presence of a catalytic amount of Ru(cod)(cot) [cod = cycloocta-1,5-diene, COT = cycloocta-1,3,5-triene] in N-methylpiperidine at 80°C to give the corresponding monoallylated carbonucleophiles in high yields with high regioselectivity. The regioselectivity was quite different from that in the palladium-catalyzed reactions. The allylation of carbonucleophiles using allyl methyl carbonate selectively gave the diallylated carbonucleophiles in high yields.