Solvent extraction of Co/II/ with isonitrosobenzoylacetone into chloroform

A rapid and selective method has been developed for the extraction of Co/II/ with isonitrosobenzoylacetone into chloroform. The effect of various parameters on the extraction coefficient value such as effect of pH, time of equilibration, effect of various cations and anions have been evaluated. The stoichiometry of metal to reagent determined by the method of substoichiometric extraction was found to be 12. It was further supported by the slope ratio method.     

Ab initio potential energy surface for Ar 3 +

The potential energy surface (PES) of linear Ar ₃ ⁺ is calculated at the MP4/6-31G* level including all single, double, triple and quadruple excitations. The results show that the PES of the linear Ar ₃ ⁺ has a very flat valley along the asymmetric stretching vibration normal mode, ν₃. A higher level quadratic configuration interaction calculation including single, double and triple substitutions QCISD (T) along this flat valley suggests that an asymmetric geometry energy minimum reported earlier based on MP2 [1] is due to symmetry breaking in UHF. The global minimum of the PES is found to be for the symmetric geometry atR _ab =R _bc =2.66±0.01 Å, which is in good agreement with the MRD-CI calculation [2] and expectations from our earlier photodissociation experiments [3]. The calculational results are compared with other theoretical calculations, and are discussed in the context of the photodissociation and dynamics of dissociation experiments conducted on Ar ₃ ⁺ .     

Flotation-spectrophotometric determination of trace of germanium with isochromatic dye ion-pairs formed by rhodamine 6G and tetrabromofluorescein

A flotation spectrophotometric method for the determination of germanium with isochromatic dye ion-pairs is described. The molar ratio of germanium to rhodamine 6G to tetrabromofluorescein is 1:5:5. The apparent molar absorptivity is 5.8 x 10(5) l mol(-1) cm(-1) at 531 nm. Beer's law is obeyed over the concentration range of 5.0 x 10(-8)-1.25 x 10(-6) mol l(-1). The proposed method is sensitive and accuracy and can be applied satisfactorily to the determination of germanium in vegetables.     

Radon in the spa of Bizovac

The radon concentration in the air and water of the Bizovac spa was measured by the Radhome silicon detector and the average values were obtained as 70 Bq/m³ in the indoor pool, 40 Bq/m³ in the hotel room, 135 Bq/m³ in the closed therapeutic bathroom, but the geothermal water had a Rn concentration of 25.3 kBq/m³ and the potable one 2.7 kBq/m³. The Rn transfer factor (f) from water to air in the indoor pool and therapeutic bathroom was 10 and 40 times higher than for normal dwellings (f _n=10^–4), respectively. The effective equivalent dose of inhaled radon for permanent personnel under the worst conditions in the spa was 5.4 mSv/y, but visitors spending two weeks in the spa could receive the dose of 77 Sv.     

Application of magdala red as a fluorescence probe in the determination of nucleic acids

A fluorescence quenching method was developed for the rapid determination of DNA and RNA using magdala red as fluorescence probe. In weakly acidic medium, the fluorescence of magdala red (lambdaex/lambdaem = 540/555 nm) can be largely quenched by DNA or RNA. The calibration graphs are linear over the range 0.01-1.2 microg/mL for both calf thymus DNA (CT DNA) and salmon DNA (SM DNA), and 0.015-1.0 microg/mL for yeast RNA, respectively. The corresponding detection limits are 6.0 ng/mL for CT DNA, 7.0 ng/mL for SM DNA and 15.0 ng/mL for yeast RNA, respectively. CT DNA could be determined in the presence of 20% (w/w) yeast RNA, and the relative standard deviation of six replicate measurements is 3.18% for 400 ng/mL of CT DNA. Interference from coexisting substances in the determination of DNA was also examined. Real samples were determined with satisfactory results.     

Calorimetric determination of the enthalpy of specific interaction of chloroform with a number of proton-acceptor compounds

Calorimetry was used to measure the enthalpies of solution of chloroform in various proton-acceptor solvents and, vice versa, proton-acceptors in chloroform. Based on a previously proposed equation, the enthalpies of specific interaction were calculated and compared with the published data on the enthalpy of hydrogen bonding of chloroform with various proton-acceptor solvents. The composition of the H-bonded complexes mainly formed during the dissolution of proton-acceptor solutes in chloroform was established. It was demonstrated that the dissolution of ethers in chloroform is predominantly accompanied by the formation of 1: 1 complexes, while the dissolution of acetone, dimethylformamide, and dimethyl sulfoxide in chloroform gives rise to more complex associates.     

1,3-Dioxa-6-chalcogena-2-silacyclooctanes

Conclusions Transetherification of methylvinyldialkoxyslianes by diols (HOCH₂CH₂)₂M (M=O, S, Se, and Te) gave 2-methyl-2-vinyl-1,3-dioxa-6-chalcogena-2-silacyclooctanes CH₃ (CH₂=CH)Si(OCH₂· CH₂)₂M. The IR, NMR, and mass spectra of these compounds were studied.²⁹Si NMR spectroscopy indicated that there is a transannular interaction in such heterocycles only in the case of M=Te.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1859–1861, August, 1987.     

Electrocatalysis of cytochrome c at a C(60)-gamma-cyclodextrin and Nafion chemically modified electrode

The C(60)-gamma-cyclodextrin and Nafion chemically modified electrode exhibits two redox waves by cyclic voltammetry. Such an electrode will effect reduction and oxidation of cytochrome c and be capable of mediating the electron transfer to cytochrome c.     

Chiral exo-Alkylidenecyclopentanes from (1S,4R)-7,7-Dimethyl-1-vinylbicyclo[2.2.1]heptan-2-one

(1S,4R)-7,7-Dimethyl-1-vinylbicyclo[2.2.1]heptan-2-one oxime in the system (CF₃CO)₂O-CF₃COOH and (1S,4R)-1-(1,2-dibromoethyl)-7,7-dimethylbicyclo[2.2.1]heptan-2-one in the system MeONa-MeOH undergo fragmentation to give exo-alkylidenecyclopentane derivatives, (4R)-4-cyanomethyl-5,5-dimethyl-1-[(1E)-trifluoroacetoxyethylidene]cyclopentane and isomeric (4R)-4-carboxymethyl-1-[(1ZE)-2-methoxyethylidene]-5,5-dimethylcyclopentanes, respectively. The trifluoroacetate derivative undergoes unusual rearrangement, yielding an equilibrium mixture of two isomers with endo- and exocyclic double bond.     

Effect of alkali ions (Na+, K+) on the solvent extraction of uranium(VI) with a di-carboxylated calix[4] arene

The solvent extraction of uranium(VI) with a di-carboxylated calix[4]arne (LH₂) in chloroform and 1,2-dichloroethane has been studied in the presence or absence of alkali ions (M=Na⁺,K⁺). For UO ₂ ²⁺ when studied alone, a 12 (metal: ligand) extracted species is evidenced, with a rather low associated extraction equilibrium constant. The efficiency of extraction increases drastically in the presence of alkali ions, due to the formation of heteronuclear complexes. In all cases, the extracted species are found to be both 122 and 112 (UO ₂ ²⁺ MLH₂) mixed complexes, except in chloroform with K⁺, where only the latter is formed. In the case of Na⁺, mass spectrometry spectra confirm the existence of both homo and heteronuclear complexes as determined in the extraction studies.