Neutral radical detection in silane glow-discharge plasma using coherent anti-stokes raman spectroscopy

RF glow discharges of silane have been investigated using CARS technique, and a weak signal assigned to the ν₁ Q-band of SiH₂ has been observed at around 2030 cm^?1 for the first time. The number density of SiH₂ in the plasma has been estimated and is discussed in relation to the magnitude of SiH₄ dissociation rate independently determined also by CARS.     

Use of a conformational radical clock for evaluating alkyllithium-mediated cyclization reactions

The reductive lithiation of nitrile 9 led to the cyclic product 11 as a single diastereomer in 42% ee. The intermediate radical is a conformational radical clock. The radical lifetime can be determined from the optical purity of the product 11. We show that the lifetime of the intermediate radical is too brief to allow a radical cyclization, and thus the cyclization proceeds through an alkyllithium intermediate.     

Difference spatial distribution function analysis of aqueous solutions. II. Hydration structures of dimethyl ether, 180 degrees ethyl methyl ether and 0 degree ethyl methyl ether solutions

Monte Carlo simulations are systematically presented to demonstrate the influence of the hydrophobic group's steric bulk on hydration structure. We have simulated a dimethyl ether (DME), two conformations for ethyl methyl ether (0 degree EME and 180 degrees EME), and 0 degree ethanol solutions. Spatial distribution function (SDF), goo(x,y,z) and difference SDF (DSDF), delta goo(x,y,z), obtained from MC simulation in an infinitely dilute aqueous solution of ether show the three-dimensional probability of an atom-atom pair distribution between solute and solvent atoms. Based on the results of SDF in an infinitely dilute aqueous solution of ether, the distribution of hydration water molecules can be divided into hydrogen acceptor (HA) and hydrophobic hydration (HH), regions, and the spatial orientation of the hydrogen-bonded water in the HA region is found to form a triple-layer structure, as it does in alcohol solutions. From the results of an analysis of the DSDF delta goo(x,y,z) between the SDFs of EME and DME, it is apparent that the distribution changes of hydration water molecules in ether solutions are essentially similar to those in the alcohol solutions. Further, we show that the hydration water molecules are distributed mainly in the stable area in the binding energy's (BE) contour maps for each region.     

Reaction of 5-amino-1-phenylpyrazole-4-carbonitriles with dimethyl acetylenedicarboxylate. Synthesis and structural determination of trimethyl 4,8-dioxo-1-phenyl-4,5,5a,8-tetrahydro-1H-pyrazolo[3,4-e]indolizine-5,5a,6-tricarboxylate derivatives

The reaction of 5-amino-1-phenylpyrazole-4-carbonitriles 1a-c with dimethyl acetylenedicarboxylate in the presence of potassium carbonate in dimethyl sulfoxide gave trimethyl 4,5,5a,8-tetrahydro-1-phenyl-4,8-dioxo-1H-pyrazolo[3,4-e]indolizine-5,5a,6-tricarboxylate derivatives 3a-c from the basic solution. The products were formed by a double Michael reaction of 1 with dimethyl acetylenedicarboxylate followed by cyclization to the cyano group. The structure of product 3a was established by X-ray crystallography.     

Synthesis of Δ1-carbapenem derivative by aldol condensation method

The Δ¹-carbapenem derivative($\text{6}$) was prepared by the aldol condensation of the dialdehydic compound($\text{5}$) with piperidinium acetate. Careful hydride reduction followed by benzoylation gave $\text{7}$b, which was successfully decarbalkoxylated to $\text{8}$. The X-ray structure analysis of $\text{8}$ showed the C-3 carboxylate group and C-5 H are $\text{cis}$ each other.     

Mononuclear and dinuclear monoperoxovanadium(v) complexes with a hetero ligand. 1.(1) Self-decomposition reaction, detection of reactive oxygen species, and oxidizing ability

A mononuclear peroxovanadium(V) complex with histamine-N,N-diacetate (histada), K[VO(O(2))(histada)], and a dinuclear peroxovanadium(V) complex with 2-oxo-1,3-diaminopropane-N,N,N',N'-tetraacetate (dpot), Cs(3)[(VO)(2)(O(2))(2)(dpot)], were prepared and characterized. The self-decomposition reaction was examined for these peroxovanadium(V) complexes as well as for K[VO(O(2))(cmhist)] (cmhist = N-carboxymethylhistidinate). The reaction profiles depicted by the absorbance change in the UV-vis spectrum show a sigmoid shape with an induction period. The induction period is reduced by the addition of acid, fluoride, thiocyanate, VO(2+), VO(2)(+), and trolox compared to the solution containing perchlorate. On the other hand, the induction period was elongated by the addition of chloride, bromide, and 2-tert-butyl-p-cresol. These behaviors are discussed on the basis of a radical chain mechanism. The self-decomposition reactions have also been followed by the (1)H and (51)V NMR and EPR spectra. These spectral studies as well as the UV-vis spectral study indicate that vanadium(V) is partly reduced to vanadium(IV) in the self-decomposition process. The histada complex yields a mixed-valence dinuclear complex in a concentrated solution, and the dpot complex yields a mixed-valence tetranuclear complex. The reduction of vanadium ion suggests that the peroxo ligand may act as a reducing agent. In order to know the fate of the peroxo ligand, we tried to detect superoxide anion and hydroxyl radical, which were anticipated to be produced in the self-decomposition process. The formation of superoxide anion was spectrophotometrically confirmed using two independent methods, including the reduction of cytochrome c and the reduction of sodium 4-[3-(iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate (WST-1). The formation of hydroxyl radical was confirmed by an EPR spin trapping technique. The oxidizing abilities of the peroxovanadium(V) complexes toward bovine serum albumin (BSA) were also evaluated. In the protein carbonyl assay, it was found that the total amount of protein carbonyl in BSA was increased by the reaction with the peroxovanadium complexes in the concentration-dependent manner. In addition, the oxidation of sulfhydryl group in BSA induced by the peroxovanadium complexes was confirmed.