Production of highly concentrated 13C by continuous two-stage IRMPD. CBr2F2/HI,CCl2F2/HI,and CBrClF2/HI mixtures

Difluoromethane CH₂F₂ containing 90–98% ¹³C was obtained in the selective IRMPD of mixtures of CBr₂F₂/HI, CCl₂F₂/HI, and CBrClF₂/HI. In CBr₂F₂/HI mixtures, the intermediate product CHBrF₂ resulting from the reaction between the initial decomposition fragment CBrF₂ and HI underwent secondary selective IRMPD to form highly ¹³C-enriched CH₂F₂ in continuous laser irradiation. The intermediate product in the mixtures of CCl₂F₂/HI and CBrClF₂/HI was found to be CHClF₂, but no significant secondary photodecomposition in CBrClF₂/HI mixtures occurred owing to the low absorption cross section of CHClF₂ at the adopted laser frequencies and fluences. The observed decomposition probabilities and selectivities under different conditions with respect to laser frequency, fluence, and partial pressures of halogenated difluoromethanes and HI suggest that CBr₂F₂ is one of the better candidates for practical ¹³C separation by IRMPD.     

Application of hydroalumination reactions in organic syntheses. coupling reactions of organoaluminum compounds with allylic halides catalyzed by copper compounds

Hydroalumination of olefins with lithium aluminum hydride followed by treatment with various allylic halides in presence of a catalytic amount of copper(I) chloride resulted in coupling. This new development provides a simple operational method for lengthening the carbon chain of olefins.     

Composite model of gauge bosons in electroweak interactions

We consider a simple Lagrangian which is constructed by only the preon and antipreon fields. By introducing the auxiliary fields φ_μ, φ _μ ^† , and ϕ_μ, it is shown that φ_μ, φ _μ ^† , and ϕ_μ correspond to the electroweak gauge bosonsW _μ ⁺ ,W _μ ⁻ , andW _μ ³ , respectively, which are composite particles of preons and antipreons.     

Critical composition of ionic–nonionic mixed micelles for counterion condensation

In the mixed micelles of an ionic surfactant (sodium dodecyl sulfate) with a nonionic surfactant (N-decanoyl-N-methylglucamide, hexaoxyethylene glycol-mono-n-decylether, and hexaoxyethylene glycol-mono-n-dodecylether), the critical mole fraction, X_ic, of the ionic surfactant has been determined, below which the counterion is completely released from the micelles. The values of X_ic are 0.074, 0.11, and 0.11, for the respective nonionic surfactants. The valences, i.e., the aggregation numbers of the ionic surfactant, of the mixed micelles at X_ic are almost close to each other, around 6. At X_ic, the critical surface charge density (about 0.03 Cm^-2) for counterion condensation was tentatively calculated. In the present study, a differential conductivity method was applied.     

Differential determination of tellurium(IV) and tellurium(VI) with sodium diethyldithiocarbamate, ammonium pyrrolidinedithiocarbamate and dithizone by atomic-absorption spectrophotometry with a carbon-tube atomizer

The extraction behaviour of tellurium(IV) and tellurium(VI) with sodium diethyldithiocarbamate, ammonium pyrrolidinedithiocarbamate and dithizone in organic solvents has been investigated by means of flameless atomic-absorption spectrophotometry with a carbon-tube atomizer. The selective extraction of tellurium(IV) and differential determination of tellurium(IV) and tellurium(VI) have been developed. With sodium diethyldithiocarbamate and carbon tetrachloride, when the aqueous phase/organic solvent volume-ratio is 5 and the injection volume in the carbon tube is 20 microl, the sensitivity for tellurium is 0.3 ng/ml for 1% absorption. The relative standard deviations are ca. 2%. The proposed methods have been applied satisfactorily to determination of tellurium(IV) and tellurium(VI) in various types of water.     

Development of new chiral building blocks for synthesis of bicyclo[3.3.0]octane compounds

Ti(II)-mediated tandem cyclization of (E)-5-(tert-butyldimethylsilyloxy)-8-trimethylsilyl-2-octen-7-ynoate (7) prepared from commercially available optically active epichlorohydrin (2) proceeded diastereoselectively to provide 7-(tert-butyldimethylsilyloxy)-2-trimethylsilylbicyclo[3.3.0]oct-1-en-3-one (1), which serves as a useful chiral building block or intermediate to prepare a variety of compounds having a bicyclo[3.3.0]octane framework.     

Rapid measurement of oestradiol and oestriol by high-performance liquid chromatography after automatic pretreatment

A fluorometric liquid chromatographic method was developed for measurements of unconjugated oestradiol and oestriol in the serum of pregnant women. The serum samples are injected directly into the apparatus and pass to a pretreatment column, where oestrogens are adsorbed while hydrophilic components such as proteins and carbohydrates are not. The oestrogens then pass into a separation column containing a new type of polymer gel. The mobile phase consists of an acetonitrile-water mixture, and separation is achieved by a reversed-phase mechanism. The eluent is monitored for fluorescence. Data on the reproducibility and recovery by this method and the correlation of values with those obtained by radioimmunoassay are reported. Results on the increases of oestradiol and oestriol in the serum during pregnancy are also reported.     

Cp2TiCl2-catalyzed grignard reactions. 3. Reactions with esters: Efficient methodology for the synthesis of secondary alcohols and for the reduction of esters to primary alcohols

Cp₂TiCl₂-catalyzed Grignard reactions with esters provide general methodology for preparation of secondary alcohols or for reduction of esters to the corresponding primary alcohols.