Studies on14CO2 exchange reaction with p-fluorophenyl acetic acid and microsynthesis of carboxyl-14C labelled p-fluorophenyl acetic acid

The exchange reaction between¹⁴CO₂ and sodium salt of p-fluorophenyl acetic acid was found to proceed with greater than 50% isotope incorporation when salt to CO₂ ratio was 61. The carboxyl-C-14 labelled p-fluorophenyl acetic acid was isolated in a pure form using small chemical concentrations of radioactive¹⁴CO₂ of high specific activity /30 mCi/mmol/.     

Structural and magnetic studies of two-dimensional solvent-free manganeseII complexes prepared via ligand exchange reaction under solvothermal conditions

Systematic investigation of the ligand exchange reactions between manganese(II) acetate and benzoic acid under solvothermal conditions led to the isolation of crystalline complexes {Mn5(OC(O)CH3)6(OC(O)C6H5)4}(infinity) ( 1) and {Mn5(OC(O)CH3)4(OC(O)C6H5)6}}(infinity) ( 2) in high (i.e., >90%) yields. The complexes are characterized structurally as 2-D honeycomb-like sheets comprised of edge-shared Mn 12 loops with some noteworthy differences as follows. First, buckling of the 2-D sheet in 1 is not observed for 2, presumably as a consequence of additional intersheet phenyl groups in the latter. Second, complex 1 is comprised of only six-coordinate MnII, while 2 has both pseudo-octahedral and distorted trigonal bipyramidal coordinate metal ions. Third, while complex 2 exhibits pi-stacking interactions with intersheet phenyl-phenyl contacts of 3.285 and 3.369 A, 1 exhibits no such bonding. Antiferromagnetic exchange is observed with Weiss constants (theta) of -28 and -56 K and Neel temperatures of 2.2 and 8.2 K for complexes 1 and 2, respectively. The paramagnetic transition at higher temperatures for complex 2 may be attributed to pi-pi exchange through phenyl groups in adjacent layers. Preliminary gas sorption studies (76 K) indidate preferential adsorption of H2 versus N2 for complex 1 only.     

Vibration-rotation infrared spectra and molecular force field of 14C labelled acetylene, 14C2H2

Infrared spectrum of ¹⁴C₂H₂ was examined under medium resolution. Rotational structures of the ν₃, ν₄¹ + ν₅¹ and ν₅ were analysed to yield values of ν₀, B′, B″ and D.Literature values of vibrational frequencies of seven isotopic species of acetylene including ¹⁴C₂H₂ were used to determine the harmonic force constants.     

Determination of leukotrienes and prostaglandins in [14C] arachidonic acid labelled human lung tissue by high-performance liquid chromatography and radioimmunoassay

A liquid chromatographic method for the determination of 14C-labelled prostaglandins, leukotrienes and other lipoxygenase products formed by human lung tissue is described. In this paper we report our problems identifying these substances when 3H- or 14C-labelled compounds are compared with measurements of the mass by absorption or radioimmunoassay. Furthermore, some preliminary results of [14C] arachidonic acid labelled human lung tissue, stimulated by the Ca-ionophore A23187, show that, of the lipoxygenase products, mostly leukotriene B4 like compounds are formed and less leukotriene C4, E4 and D4. Relatively large amounts of hydroxyeicosatetraenoic acids are present. The main cyclooxygenase products are thromboxane B2, 6-ketoprostaglandin F1 alpha and prostaglandin D2.     

Chromatographic and biological comparison of99mTc-DMSA prepared by direct labelling and ligand exchange reaction

^99mTc-dimercaptosuccinic acid /DMSA/ is one of the most favourable agents used for renal scintigraphy. This radiopharmaceutical was prepared in two different ways: by direct labelling of tin/II/-dimercaptosuccinic acid and by ligand exchange reaction from^99mTc-gluconate at tracer concentration of technetium under acidic condition. The complexes formed were compared using paper chromatography, thin layer chromatography, gel filtration and electrophoresis. Their biodistribution was studied on rats.     

Access to 14C-Ring labelled phenothiazines. Synthesis of 2-chlorophenolhiazine-5a,9-14C

Through the use of a recently reported ring expansion reaction, a new route to phenolhiazines has been developed suitable for the preparation of ring labelled derivatives. As an example, the preparation of 2-chloropheno thiazine-5a,9-¹⁴C ( 1 ) is reported. Condensation of cyclohexanone-2-¹⁴C with 2-amino-4-chlorothiophenol gave the spiro-2,3-dihydro-l, 3-benzothiazole 4 which was protected by acetylation ( 5 ). Treatment of 5 with sulfuryl chloride gave the tetrahydro-phenothiazine olefin mixture 6 and 7 which was directly converted to labelled 1 via treatment with DDQ in refluxing benzene followed by hydrolysis of the acetyl group.     

Adsorption and reaction studies on cobalt/alumina catalysts prepared by changing pH coprecipitation

Co/Al₂O₃ catalysts prepared by changing pH coprecipitation with Co loadings in the 8.7–36 wt.% range were analyzed by TSA, TPV, pore structure, XRD as well as CO, H₂, O₂ adsorption and CO hydrogenation. High O₂ uptake and reducibility coupled with low dispersion and constant MSA above 17 wt.% Co indicate large crystallites that are less exposed to H₂. CO hydrogenation per Co site decreases with increasing dispersion or decreasing metal loading.     

Aromatic ring favorable and efficient H-D exchange reaction catalyzed by Pt/C

An effective and applicable Pt/C-catalyzed deuteration method of aromatic rings using D₂O as a deuterium source under hydrogen atmosphere was developed. Five percent Pt/C would lead to quite effective H-D exchange results on the aromatic ring systems. The reaction is general for a variety of aromatic compounds including biologically active compounds.     

Isotope exchange reaction in uranous-uranyl-sulphuric acid system Catalytic effect of Fe(II) on the exchange reaction

Our previous paper reported the effect of acidity and temperature on uranous-uranil isotope exchange reaction in sulphuric acid solution.¹ It was found that the half-life of the isotope reactiont _1/2 is around 10 seconds, when the acidity and the temperature of the reaction system are reasonably selected. However, when the uranium isotopes are enriched by ion exchange the single separation factor could be 1.001. Thus, the half-life,t _1/2 is less than one second for potential industrial application.     

Degradation of phenylarsonic acid and its derivatives into arsenate by hydrothermal treatment and photocatalytic reaction

The degradation of phenylarsonic acid (PA) and its derivatives by hydrothermal treatment (HTT) was examined, especially focusing on the effect of adding H₂O₂ upon the degradation efficiency. The degradation was assessed by the generation of arsenate resulting from the cleavage of As C bonds in the PA derivatives. When PA (without substituents) was subjected to an HTT with H₂O₂ (H₂O₂‐HTT; 0.5–1% H₂O₂) at 175–200 °C, PA was almost completely degraded into arsenate, whereas an HTT with NaOH (NaOH‐HTT; 3 M NaOH) at the temperatures provided almost no degradation. The H₂O₂‐HTT also worked well for the degradation of PA derivatives with hydroxy and/or nitro groups on the phenyl ring. However, the degradation of aminophenylarsonic acids was not favorably performed by the H₂O₂‐HTT. The effect of the structure of PA derivatives upon the degradation susceptibility was discussed. A photocatalytic reaction using TiO₂ was also attempted for the degradation of PA derivatives. Copyright © 2005 John Wiley & Sons, Ltd.     

Surface modification with phosphoric acid of SiO2/Nb2O5 prepared by the sol-gel method: structural-textural and acid sites studies and an ion exchange model

In this work, the structural and textural properties of the SiO2/Nb2O5 system prepared by the sol-gel method and then modified by phosphoric acid were studied. The different materials were prepared, with three different mol % Nb2O5 (2.5, 5.0, and 7.5 mol %), and calcined in the temperature range of 423-1273 K. BET specific surface area determinations, scanning electron microscopy connected to a X-ray emission analyzer, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS) were used for the investigation. For the lowest temperature of calcination (423 K), the mesopores and micropores of the modified material were blocked, resulting in a decrease of the specific surface area compared to the SBET values obtained for the SiNb matrix. Under intermediate temperatures of calcination (423-873 K), the modified material acquired textural stability. By XPS analysis, the presence of the dihydrogenphosphate species was identified, the P/Nb atomic ratios being independent of the thermal treatment. 31P magic angle spinning NMR confirmed the XPS data and also showed that the chemical shift of the (H2PO4)- ions strongly depended on the crystallization degree of the Nb2O5. Structural thermal stability was also shown by the presence of Br?nsted acid sites in the modified material calcined at high temperature (1273 K). The thermal stability is directly associated with obtainment of the same value for K+ exchange capacity (0.74 mmol g(-1), average value) for the modified materials calcined at 423 and 1273 K. The chemical analyses of phosphorus for the modified materials were made by using the inductively coupled plasma. The value was 0.36 mmol g(-1), corroborating the presence of (H2PO4)- ions. The ion exchange isotherms presented an S-shaped form characteristic of energetically heterogeneous ion exchangers, permitting application of a model of fixed polydentate centers, in which ion exchange took place.     

Synthesis of labelled dihydroartemisinic acid

[15-¹³C²H₃]-Dihydroartemisinic acid (2a), [15-C²H₃]-dihydroartemisinic acid (2b) and [15-¹³CH₃]-dihydroartemisinic acid (2c) have been obtained in good yield and high isotopic enrichment by a reconstructive synthesis from artemisinin. These labelled compounds were designed to be used in biosynthetic experiments to determine the origins of artemisinin and other sesquiterpene natural products from Artemisia annua.     

A new promising Pt(Mo2C) catalyst for hydrogen evolution reaction prepared by galvanic displacement reaction

Journal of Solid State Electrochemistry - A new method for the synthesis of Pt(Mo2C) catalysts using the redox reaction between Mo2C and solution containing potassium tetracholoplatinate (II) is...     

The problem of adsorption on silicagel in a liquid scintillation radiometry of14C labelled compounds

By means of liquid scintillation spectrometry we investigated the counting efficiency of the samples containing toluene solution of scintillator (PPO, butyl-PBD, PT) and 1-methyl[2−¹⁴C]imidazolidinone-2 adsorbed on the silicagel, depending on concentration of scintillator, mass of radioactive compound, and mass of another nonactive compound introduced to samples as an impurity. For the sake of comparison the efficiency of counting homogeneous samples and the ones with Ba¹⁴CO₃ deposit was determined. It was found, that the efficiency of detection of a radioactive compound adsorbed on the silicagel is conditioned by composition of adsorptive layer on the support surface.     

Substituted dialkylaminomethylphenols in an exchange reaction with carboxylic acid anhydrides

Carboxylic acid benzyl esters are formed in the reaction of carboxylic acid anhydrides with N,N-dialkyl-4(2)-hydroxy-substituted benzylamines. 4-Hydroxy-3,5-di-tert-butylbenzyl acetate exchanges an acetyl fragment for an alkoxyl fragment and benzylates phenol derivatives in the presence of an acid.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2765–2770, December, 1989.