Anodic oxidation of silver in 1-butyl-3-methylimidazolium bromide ionic liquid

Electrochemical oxidation of silver in the 1-butyl-3-methylimidazolium bromide ([BMIm]Br) ionic liquid is studied by cyclic voltammetry, chronopotentiometry, chronoammetry, and gravimetry. Two electrode processes irreversibly proceed on the silver electrode in the potential range studied: the formation of compound [BMIm]⁺[AgBr₂]^?, which is soluble in [BMIm]Br, and difficultly soluble AgBr.     

Co3{CH3C(NH3)(PO3H)(PO3)}2 {CH3C(NH3)(PO3H)2}2(H2O)4·2H2O: A cobalt 1-aminoethylidenediphosphonate with a layer structure

This paper describes the structure and magnetic properties of a novel cobalt 1-aminoethylidenediphosphonate compound, namely Co₃{CH₃C(NH₃)(PO₃H)(PO₃)}₂{CH₃C(NH₃)(PO₃H)₂}₂(H₂O)₄·2H₂O (1). The structure contains a trimer unit of Co₃{CH₃C(NH₃)(PO₃H)(PO₃)}₂ in which two equivalent phosphonate ligands chelate and bridge the three cobalt ions. Each trimer unit is further linked to its four equivalent neighbors through corner-sharing of CoO₆ octahedra and CPO₃ tetrahedra, forming a two-dimensional layer in the bc-plane which contains 12-membered rings. These layers are connected to each other by extensive hydrogen bonds. Magnetic studies show that weak antiferromagnetic interactions are mediated between the cobalt ions. Crystal data for 1: monoclinic, space group C2/c, a=27.727(4), b=7.1091(11), , β=118.488(3), , Z=2.     

2-{[1-(3,4-Dihydroxyphenyl)methylidene]amino}benzoic acid immobilized Amberlite XAD-16 as metal extractant

2-{[1-(3,4-Dihydroxyphenyl)methylidene]amino}benzoic acid (DMABA) was loaded on Amberlite XAD-16 (AXAD-16) via azo linker and the resulting resin AXAD-16-DMABA explored for enrichment of Zn(II), Mn(II), Ni(II), Pb(II), Cd(II), Cu(II), Fe(III) and Co(II). The optimum pH values for extraction are 6.5-7.0, 5.0-6.0, 5.5-7.5, 5.0-6.5, 6.5-8.0, 5.5-7.0, 4.0-5.0 and 6.0-7.0, respectively. The sorption capacity was found between 97 and 515 μmol g⁻¹ and the preconcentration factors from 100 to 450. Tolerance limits for foreign species are reported. The kinetics of sorption is fast as t_1/2 is ≤5 min. The chelating resin can be reused for 50 cycles of sorption-desorption without any significant change (<1.5%) in the sorption capacity. The limit of detection values (blank +3 s) are 1.12, 1.38, 1.76, 0.67, 0.77, 2.52, 5.92 and 1.08 μg L⁻¹ for Zn(II), Mn(II), Ni(II), Pb(II), Cd(II), Cu(II), Fe(III) and Co(II), respectively. The enrichment on AXAD-16-DMABA coupled with monitoring by flame atomic absorption spectrometry (FAAS) is used to determine all the metal ion ions in river and synthetic water samples, Co in vitamin tablets and Zn in milk samples.     

Preparation and stereoselectivity of 1,3-dipolar cycloaddition ofD-glucose-derived nitrones to N-arylmaleimides

Summary Nitrones2 derived fromD-glucose oxime and benzaldehydes without employing any protection of hydroxyl group were isolated in pure state. The 1,3-dipolar cycloaddition of2 to N-arylmaleimides gave predominantly theanti isoxazolidines3 and was rationalized byZ/E isomerization of N-glycosylnitrones2. The structure and steric configuration of the products have been assigned on the basis of¹H- and¹³C-NMR spectroscopy. AM1 calculations of the nitrones and MM2 calculations of the adducts were performed.

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Darstellung und Stereoselektivität der 1,3-dipolaren Cycloaddition vonD-Glucose-abgeleiteten Nitronen an N-Arylmaleimiden

Zusammenfassung Die Nitrone2 wurden ausD-Glucoseoxim und Benzaldehyden ohne Schutz von Hydroxylgruppen in reinem Zustand erhalten. Die 1,3-dipolare Cycloaddition von2 an N-Arylmaleimiden ergab bevorzugt dieanti-Isoxazolidine3; dies wurde über eineZ/E-Isomerisierung der N-Glycosylnitrone2 rationalisiert. Struktur und Stereochemie wurden auf Basis von¹H- und¹³C-NMR-Spektroskopie ermittelt. Außerdem wurden AM1-Berechnungen an den Nitronen und MM2-Rechnungen an den Addukten ausgeführt.

     

Photochemical synthesis of 2-amino-1-hydroxy-9,10-anthraquinone-9-alkyl(aryl)imines

Irradiation of a mixture of 1-aryloxy-2-amino-9,10-anthraquinone and amines in benzene results in formation of the derivatives of 2-amino-1-hydroxy-9,10-anthraquinone-9-alkyl(aryl)imines in a high yield. 2-Amino-1-hydroxy-9,10-anthraquinone-9-aikylimines were shown by¹³C and¹⁵N NMR to exist predominantly in the enaminoquinoid form whereas 2-amino-1-hydroxy-9,10-anthraquinone-9-arylimines exist in the oxyimine form. Sunlight irradiation of the derivatives of 2-benzoylamino-9,10-anthraqumone-9-alkylimines results in formation of the photocyclization products — 4-benzoylaminoanthra-[9,1-d,e]-1,3-oxasinones-7.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 940–944, May, 1993.     

Nucleosides 4: Synthesis of 2′,3′-Didehydro-2′,3′-dideoxydoridosine and 2′,3′-Dideoxydoridosine as Potential Antihypertensive Agents

To measure the hydrophobic character of the ribose moiety of doridosine on the adenosine receptors, 2′,3′-didehydro-2′,3′-dideoxydoridosine (2) and 2′,3′-dideoxydoridosine (3) were prepared. Initial treatment of doridosine with N,N-dimethylformamide diethylacetal, and subsequently with tert-butyldimethylsilyl chloride gave 5. Compound 5 was then reacted with 1,1′-thiocarbonyldiimidazole and the resulting thionocarbonate 6 was heated with triethyl phosphite at 135°C to afford 7. Treatment of compound 7 with tetrabutylammonium fluoride and methanolic ammonia furnished compound 2 in good yield. Compound 2 was subjected to catalytic hydrogenation affording compound 3 in 85% yield.     

Oxidation-Induced Structural Alterations and Its Effect on Chaperone Function of Rat Lens α-Crystallin

An ascorbate-FeCl₃-EDTA-H₂O₂ system was used to oxidize rat lens α-crystallins. Under this oxidative insult, the chaperone activity of α-crystallin toward γ-crystallin was shown to decrease significantly, which is quite different from the result reported by Wang and Spector. (Invest. Ophthalmol. Vis. Sci. 1995 , 36, 311-321.) Fluorescence spectroscopy and circular dichroism were employed to characterize the structural changes of oxidized α-crystallin. It was found that fluorescence intensity of l-anilinonaphthalene-8-sul-phonate (ANS) bound to oxidized α-crystallin increased comparing to that bound to normal α-crystallin, suggesting oxidation causes the exposure of more hydrophobic regions. Further, α-crystallin's fluorescence intensity in response to tryptophan residues showed a pseudo first order decline. Amino acid analysis of normal versus oxidized α-crystallin confirmed actual decline in tryptophan levels, showing about 80% of tryptophan being modified after 10-hour oxidation. Circular dichroism showed both changes in the secondary and tertiary structures of oxidized α-crystallin, characterized by a large loss of aromatic-type amino acid interactions and a large loss of β-sheet structure. In conclusion, modified tryptophan, secondary and tertiary structural changes of α-crystallin correlate best with the reduction of chaperone function, the curves all showing a linear slope for 10 hours, then plateauing. These results indicate that the decrease of α-crystallin chaperone activity is attributed to the structural changes.     

离子液体存在下脂肪醛的环化三聚反应

Aliphatic aldehydes such as ethanal,propanal,n-butanal,isobutyraldehyde,n-valeraldehyde,isovaleraldehyde,n-hexanal and n-octanal were converted into the corresponding 2,4,6-trialkyl-1,3,5-trioxanes through cyclotrimer-ization in the presence of the ferric chloride based ionic liquids at room temperature without solvent in high selec-tivity.The effects of different ionic liquids,acidity of ionic liquids and temperature on cyclotrimerization were alsostudied.The results showed that the ferric chloride based ionic liquids(apparent molar fraction of FeCl_3(x(FeCl_3)=0.62))were a kind of efficient catalysts for the cyclotrimerization of aliphatic aldehyde which could be separatedconveniently from the reaction mixture and recycled without loss of catalytic activity.The conversion of isobu-tyraldehyde and the selectivity to 2,4,6-triisopropyl-1,3,5-trioxane were 91.1% and 99.8% respectively under opti-mum reaction condition(isobutyraldehyde 25.0 g,[Et_3NH]Cl/FeCl_3(x(FeCl_3)=0.62)1.0 g,25 ℃for 1 h).     

Effect of 1,1,2,2-tetrachloroethane on IR spectra of HCl complexes withN,N-dimethylformamide and 1-methyl-2-pyrrolidone formed by a strong quasi-symmetric hydrogen bond

The effect of 1,1,2,2-tetrachloroethane (TCE) on the IR spectra of HCl complexes withN,N-dimethylformamide (DMF) and 1-methyl-2-pyrrolidone (N-MP) with strong quasisymmetric hydrogen bonds was studied using Multiple Attenuated Total Reflection (MATR) IR spectroscopy. The addition of TCE does not change the background absorption spectra, but results in a change in the extinction coefficients of some bands of these complexes. The analysis of the spectra shows that the HCl−DMF complexes interact only with one molecule of TCE, and the HCl−N-MP complexes interact with two molecules of TCE. It is shown that the neutral component of the system (TCE) has no effect on the parameters of the strong quasi-symmetric H-bond in the complexes studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 956–960, May, 1997.     

Synthesis of 1,1-dihydroperfluorooxaalkan-1-ols and their interaction with terephthaloyl chloride

A series of 1,1-dihydroperfluorooxaalkan-1-ols and ,,,-tetrahydroperfluorooxaalkanediols has been synthesized. Some tercphthalates were synthesized by the reaction of these alcohols and diols with terephthaloyl chloride.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1573–1576, June, 1996.