An ethoxy intermediate in ethanol dehydration on Brønsted acid sites in zeolite

Acid-catalyzed ethanol dehydration on zeolite is shown to proceed via a covalent ethoxy group (C2H5O) as a stable intermediate, which was directly observed by IR spectroscopy.     

Cluster-glass like behavior of the diluted antiferromagnet Fe0.26Zn0.74F2

The temperature variations of magnetizations and Mössbauer spectra of the diluted antiferromagnet Fe_0.26Zn_0.74F₂ have been studied. It has been shown that the temperature variation of the Mössbauer spectra is nicely explained in an aspect of dynamical behavior of the antiferromagnetic (AF) clusters. By combining the results of the magnetization and Mössbauer measurements, it is inferred that the spin-glass like freezing of the AF clusters, but not individual spins, occurs atT _f=9.7 K.     

Spectral Analysis of Stochastic Phase Lockings and Stochastic Bifurcations in the Sinusoidally Forced van der Pol Oscillator with Additive Noise

Noise effects on the phase lockings and bifurcations in the sinusoidally forced van der Pol relaxation oscillator are investigated. Deterministic (noise-free) one-dimensional Poincaré mapping is extended to the iteration of the operator defined by a stochastic kernel function. Stochastic phase lockings and bifurcations are analyzed in terms of the density evolution by the operator. In particular, a new method which uses spectra (eigenvalues and eigenfunctions) of the operator to analyze stochastic bifurcations intensively is proposed.     

Comparison of recent massive muon pair data with the asymptotically free parton model

We present calculations of vW₂ and of massive muon pair production cross sections in the kinematic ranges of recent experiments. These calculations test the asymptotically free parton model and excellent agreement with the data is found. Estimates of the transverse momentum 〈q_⊥〉_μμ expected in massive dimuon experiments are made. For s = 750 GeV² and M_μμ ≈ 10 GeV, we predict 〈q_⊥〉_μμ ≈ 1.4 GeV/c.     

Highly selective double chalcogenation of isocyanides with disulfide-diselenide mixed systems

A highly selective method for introducing thio and seleno groups into a variety of isocyanides has been developed based on the elucidation of the relative reactivities of organic dichalcogenides and chalcogen-centered free radicals. When the reactions of aromatic isocyanides (ArNC) with organic disulfides (R'SSR') and diselenides (R'SeSeR') are conducted upon irradiation with a tungsten lamp through Pyrex (hnu>300 nm), simultaneous introduction of both thio and seleno groups into the isocyanides takes place to provide the corresponding thioselenation products (R'S-C(=NAr)-SeR') in good yields with excellent selectivity. In the cases of aliphatic isocyanides (RCN), a novel diselenide-assisted bisthiolation of RNC with diaryl disulfides (Ar'SSAr') proceeds successfully to give the corresponding bisthiolation products (Ar'S-C(=NR)-SAr'), although the same photoirradiated reaction of RNC with diaryl disulfides does not occur in the absence of diselenide. These double chalcogenation reactions are assumed to proceed via the formation of imidoyl radical intermediates by the reaction of isocyanides with relatively reactive thio radicals (compared with seleno radicals). The obtained thioselenation products can be employed as useful precursors for the construction of beta-lactam framework by the formal [2+2] cyclization with ketene equivalents.     

Successful preparation of metabolite of troglitazone by in-flow electrochemical reaction on coulometric electrode

A simple, rapid and efficient system utilizing a coulometric electrode was developed for the preparation of drug metabolites. Trace amounts of reactants are usually generated in electrochemical reactions, which are not suitable for the sufficient preparation of products to obtain NMR and other spectral data for chemical structure confirmation or to obtain data from pharmacological activity screening tests of products. In the developed system, called the "in-flow electrochemical reaction system," a drug, troglitazone, was dissolved in a volatile flow solvent, and pumped into a coulometric electrode under optimized conditions, and the effluent was evaporated. Without any further purification, milligram amounts of a pure oxidation product of troglitazone could be obtained within several hours. The amount obtained was enough for (1)H- and (13)C-NMR analysis by which the structure could be confirmed and was found to be identical to one of the metabolites of troglitazone detected in human plasma. This system will be useful to prepare standard compounds of the required amount for pharmacokinetic study and for toxicokinetic study.     

Chiral Bis(oxazoline) Ruthenium Complexes with Bipyridyl‐Type N‐Heteroaromatics: Comparative Stereochemical and Photochemical Characterization of their Λ‐ and Δ‐Diastereomeric Geminate Isomers

Diastereomeric geminate pairs of chiral bis(2‐oxazoline) ruthenium complexes with bipyridyl‐type N‐heteroaromatics, Λ‐ and Δ‐[Ru(L‐ L)₂(iPr‐biox)]²⁺ (iPr‐biox=(4S,4′S)‐4,4′‐diisopropyl‐2,2′‐bis(2‐oxazoline); L‐ L=2,2′‐bipyridyl (bpy) for 1 Λ and 1 Δ, 4,4′‐dimethyl‐2,2′‐bipyridyl (dmbpy) for 2 Λ and 2 Δ, and 1,10‐phenanthroline (phen) for 3 Λ and 3 Δ), were separated as BF₄ and PF₆ salts and were subjected to the comparative studies of their stereochemical and photochemical characterization. DFT calculations of 1 Λ and 1 Δ electronic configurations for the lowest triplet excited state revealed that their MO‐149 (HOMO) and MO‐150 (lower SOMO) characters are interchanged between them and that the phosphorescence‐emissive states are an admixture of a Ru‐to‐biox charge‐transfer state and an intraligand excited state within the iPr‐biox. Furthermore, photoluminescence properties of the two Λ,Δ‐diastereomeric series are discussed with reference to [Ru(bpy)₃]²⁺.