Unprecedented alkylation of silicon enolates with alcohols via carbenium ion formations catalyzed by tin hydroxide-embedded montmorillonite

The solid acid, tin hydroxide-embedded montmorillonite, catalyzes the unprecedented alkylation of various silicon enolates with primary, secondary and tertiary benzylic alcohols as well as secondary allylic alcohols. The acid catalysis of Sn-Mont was not only higher than that of the other ion-exchanged montmorillonites (M-Mont; M = H, Ti, Fe and Al), but also higher than that of the typical homogeneous acid catalysts such as BF₃·OEt₂, TMSOTf and TfOH.     

Analysis of the Dynamic Decomposition of Unsaturated Fatty Acids and Tocopherols in Commercial Oils During Deep Frying

The decomposition of unsaturated fatty acids and tocopherols in 10 commercial edible oils during deep frying was investigated. The dominant tocopherol in oils rich in polyunsaturated fatty acids (PUFAs) was γ-tocopherol, except for natural perilla oil (δ-tocopherol dominant), and the main tocopherol in oleic acid-rich oils was α-tocopherol. The PUFA-rich oils had higher tocopherol contents than the oleic acid-rich oils. Both the reduction rate of total unsaturated fatty acid (TUFA) and total tocopherol (TToc) were linear with frying time (t). The decomposition rate of TToc is faster than that of TUFA since the slope values obtained from fitting equations (Y?=?k t) k_TToc (1.520–14.483) were obviously larger than for k_TUFA (0.155–0.270). By establishing a dynamic decomposition index, unsaturated fatty acids and tocopherol in oils showed dynamic decomposition over multiple frying cycles. The obtained results showed that decomposition characteristics of oils are related to their fatty acid compositions.     

Superconducting gap of overdoped Tl2Ba2CuO6+δ observed by Raman scattering

We report Raman scattering spectra for single crystals of overdoped Tl₂Ba₂CuO_6+δ (Tl-2201) at low temperatures. It was observed that the pair-breaking peaks in A_1g and B_1g spectra radically shift to lower energy with carrier doping. We interpret it as s-wave component mixing into d-wave, although the crystal structure is tetragonal. Since similar phenomena were observed also in YBa₂Cu₃O_y and Bi₂Sr₂CaCu₂O_z, we conclude that s-wave mixing is a common property for overdoped high-T_c superconductors.     

Anion-selective properties of alkali metal-free lead phosphate glasses containing silver chloride and their application in an ion-selective electrode

Alkali-free lead phosphate glasses containing silver chloride have been developed for anion responsive sensors. From measurements of the final glass compositions by electron probe microanalysis, it became clear that some of chloride ions in the glass bulk were not volatilized during the glass melting process. Compared with phosphate glasses containing silver oxide, the new glass electrodes containing silver chloride could respond more rapidly, although the response behaviour for anionic species were similar. From the electrode potential vs. time curve for the anionic species, the potential rapidly reached equilibrium when these concentrations varied from 10^?5 to 10^?2 M. The response times, t₉₅, to thiocyanate of the new glass electrode and the phosphate glass electrode containing silver oxide were 30 and 110 s, respectively. Moreover, the response time required for an initial potential change with a concentration jump of thiocyanate with the new glass electrode was found to be independent of the membrane thickness within about 2 mm and of the measuring temperature between 15 and 40°C. It is concluded that the diffusion process of species such as silver ion in the glass bulk does not take part in the initial part of the response behaviour.     

Advanced materials for environmental catalysts

Recent advances in the synthesis and characterization of materials for environmental catalysts are reported in this paper. Highly advanced environmental catalysts for decomposition of volatile organic compounds and nitrogen oxides were artificially designed based on a concept usually employed in the fields of solid‐state chemistry and solid‐state ionics. Catalytically active materials for complete ethylene oxidation were prepared by a citrate sol‐gel method as a key process to obtain CeO₂? ZrO₂? Bi₂O₃ solid solutions. On the other hand, direct NO decomposition catalysts were designed and prepared focusing on the open spaces and oxide anion vacancies in the crystal lattice. Evaluation of the materials as environmental catalysts demonstrated significant advantages over the conventional ones. The design strategy, synthetic method, and structural features of these concerto catalysts are addressed. © 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 9: 40–50; 2009: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20167     

Electrochemical acylation and alkylaminocarbonylation of amines and alcohols

Electrochemical acylation and ethylaminocarbonylation of amines and alcohols are performed by anodic oxidation of the hydroxamic acids and N-ethyl-N′hydroxyurea, respectively, in acetonitrile at a glassy-carbon electrode.     

Selective resonant enhancement in the two-phonon Raman spectrum of Si and GaP

Resonant enhancement of selective pairs of phonons has been observed by noting the changes in the lineshape of the two-phonon Raman spectrum from Si and GaP as the incident photon energy is made resonant with the indirect energy gap. These selective phonons have the same k as those that are involved in the phonon-assisted optical transition.     

Rapid additions of bulky tert-butyldimethylsilyl cyanide to hindered ketones promoted by heterogeneous tin ion-exchanged montmorillonite catalyst

Tin ion-exchanged montmorillonite (Sn-Mont) was found to be a powerful heterogeneous catalyst for the cyanosilylation of various ketones including congested ones with a bulky cyanide source, tert-butyldimethylsilyl cyanide (TBDMSCN), giving the corresponding cyanohydrin tert-butyldimethylsilyl ethers in good (85%) to excellent (>98%) yields at room temperature. Compared to the previously reported catalysts, Sn-Mont is easy to prepare, environmentally benign, nontoxic, noncorrosive, and recyclable.     

Oxygen isotope effect in optimally doped Bi2Sr2CaCu2O8+δ studied by low-energy ARPES

Using angle-resolved photoemission spectroscopy (ARPES) with low-energy tunable photons, we studied the oxygen isotope effect in optimally doped Bi₂Sr₂CaCu₂O_8+δ (Bi2212). We found the oxygen isotope shift in the real part of the electron self-energies [ReΣ(ω)s] along the nodal direction derived not only from the momentum distribution curves (MDCs) but also from the energy distribution curves (EDCs). Present results indicate straightforwardly the coupling between the nodal electrons and the phonons.     

Binuclear 1,2,4,5-tetraimino-3,6-diketocyclohexane bis[bis(bipyridine)ruthenium(II)] redox series

The reaction of the [Ru(bpy)2(MeOH)2]2+ cation (bpy = 2,2'-bipyridine) with 1,2,4,5-tetraaminobenzene in the presence of trace water and oxygen yields the cation [(bpy)2Ru(1,2,4,5-tetraimino-3,5-diketocyclohexane)Ru(bpy)2]4+. This binuclear species undergoes ligand-based reductions, giving the 3+ and 2+ charged species. The X-ray structure, electrochemistry, ZINDO calculations, and NMR, ESR, UV/vis, and IR spectra were analyzed where possible, giving an electronic model of the binuclear species and some of its redox products. The X-ray structure reveals the [(bpy)2Ru] fragments symmetrically disposed across the 1,2,4,5-tetraimino-3,5-diketocyclohexane bridge in a molecule with Cs symmetry.