Hydroxyl radical mediated degradation of phenylarsonic acid

Phenyl-substituted arsonic acids have been widely used as feed additives in the poultry industry. While very few studies have been reported on the environmental impact of these compounds, they have been introduced into the environment through land application of poultry litter in large quantities (about 10(6) kg/year). Phenylarsonic acid (PA) was used as a model for problematic arsonic acids. Dilute aqueous solutions of PA were subjected to gamma radiolysis under hydroxyl radical generating conditions, which showed rapid degradation of PA. Product studies indicate addition of (.)OH to the phenyl ring forms the corresponding phenols as the primary products. Arsenite, H3As(III)O3, and arsenate, H3As(V)O4, were also identified as products. The optimized structures and relative calculated energies (using GAUSSIAN 98, the B3LYP/6-31G(d) method) of the various transient intermediates are consistent with the product studies. Pulse radiolysis was used to determine the rate constants of PA with (.)OH (k = 3.2 x 10(9) M(-1) s(-1)) and SO4(.-) (k = 1.0 x 10(9) M(-1) s(-1)). PA reacts slower toward O(.-) (k = 1.9 x 10(7) M(-1) s(-1)) and N3(.) (no detectable transient), due to the lower oxidation potential of these two radicals. Our results indicate advanced oxidative processes employing (.)OH and SO4(.-) can be effective for the remediation of phenyl-substituted arsonic acids.     

Separation of niobium and tantalum with phenylarsonic acid

Phenylarsonic acid permits satisfactory separation of niobium and tantalum and estimation of tantalum from an oxalate solution containing sulphuric acid up to pH 5.8. For complete precipitation of niobium the pH should exceed 4.8. In mixtures, tantalum is precipitated below pH 3.0 and niobium is then precipitated above pH 5.0. When the oxalate concentration is high, recovery of niobium with cupferron is recommended. When the ratio of Nb₂O₅, to Ta₂O₅ exceeds 2:1, reprecipitation of tantalum is necessary. The effect of interfering ions is studied.     

Synthesis of ortho- and meta-Re(I)-metallocarboranes in water

A series of metallocarboranes of the types rac-[M(CO)3(eta(5)-7-R-7,8-C2B9H11)]-, rac-[M(CO)3(eta(5)-7-R-8-R'-7,8-C2B9H11)]-, and rac-[M(CO)3(eta(5)-7-R-7,9-C2B9H11)]- (M=Re) were prepared by reacting [NEt4]2[Re(CO)3Br3] or [Re(CO)3(OH2)3]Br with the corresponding carboranes in the presence of aqueous solutions of either alkali metal or tetraalkylammonium fluoride salts. Carborane derivatives that were investigated included those containing pyridine, amino, carboxylic acid, carbohydrate, and aryl substituents. During the course of the research, it was discovered that Re metallocarboranes can be prepared directly from the respective closo-clusters under similar reaction conditions used with nido-carboranes. Reaction yields ranged from modest to excellent depending on the carborane isomer and the nature of the cage substituent(s). A crystal structure of an amine-substituted Re metallocarborane was obtained where the complex crystallized in the orthorhombic space group P2(1)2(1)2(1) with a=8.982(2) A, b=11.563(3) A, c=16.811(4) A, alpha=beta=gamma=90 degrees, V=1746.1(7) A3, Z=4, and R1=0.0684.     

Benzoyl hydrazone derivatives of niobium(V) and tantalum(V) ethoxides

Summary Niobium(V) and tantalum(V) pentaethoxides react with monofunctional benzoyl hydrazones (BHy) in refluxing benzene to give products of the type, M(OEt)_5–n(BHy)_n (where M=Nb or Ta and n=1, 2 or 3). The complexes have been characterised on the basis of elemental analysis, spectral (i.r. and n.m.r.) and molecular weight data.     

Chiral Single-Molecule Potentiometers Based on Stapled ortho- Oligo(phenylene)ethynylenes

We report on the chemical design of chiral molecular junctions with stress-dependent conductance, whose helicity is maintained during the stretching of a single molecule junction due to the stapling of both ends of the inner helix. In the reported compounds, different conductive pathways are observed, with clearly different conductance values and plateau-length distributions, attributed to different conformations of the helical structures. The large chiro-optical responses and the potential use of these molecules as unimolecular spin filters have been theoretically proved using state-of-the-art Density Functional Theory (DFT) calculations, including a fully ab-initio estimation of the CISS-originating spin polarization which is done, for the first time, for a realistic molecular system.     

Characterization Reaction of Benzoyl Methylene Triphenylphosphorane and Benzoyl Methylene Tri-n-buthylphosphorane with Rhodium (III) and Ruthenium (III) Chloride. A Multinuclear NMR Study

The reactions of title ylide (C 6 H 5 ) 3 PCHCOC 6 H 5 , (BPPY) and (n-C 4 H 9 ) 3 PCHCOC 6 H 5 , (BBuPY) with rhodium (III) and ruthenium (III) chloride in equimolar ratios using methanol as solvent have yielded crystals of [(BPPY-H) 3 Rh], ( 1 ), [(BPPY) 2 Ru(MeOH) 2 (H 2 O) 2 ]Cl 3 , ( 2 ), and [Ru(BBuPY)Cl 2 S 2 ]Cl (S = H 2 O or CH 3 OH), ( 3 ). The IR and 1 H, 13 C, 31 P NMR data of the products were obtained. Analytical and NMR data are consistent with the cyclometalated and octahedral structures for ( 1 ) and ( 2 ) respectively.     

Intramolecular cyclization of ortho-(cyclohex-2-enyl) anilines synthesis of ellipticine

A convenient method is proposed for the synthesis of the alkaloid ellipticine, which possesses a pronounced antitumoral activity. The interaction of 3-bromocyclohexene (1 equiv.) and 2,5-xylylidine (4 equiv., 150°C, 5 h) gave a mixture of hexa- and tetrahydrocarbazoles which was dehydrogenated in the presence of Pd/C to the key synthon 1,4-dimethylcarbazole. The formylation of the carbazole by the Vilsmeier-Haack reaction, interaction with 2,2-diethoxyethylamine, and reduction of the imine formed over Raney nickel led to 3-(2,2-diethoxyethylaminomethyl)-1,4-dimethylcarbazole, the boiling of the N-tosylate of which gave ellipticine in high yield.Institute of Organic Chemistry, Urals Branch, Russian Academy of Sciences, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 549–554, September–October, 1992.     

Complexes of diphenylarsinic acid and phenylarsonic acid with thiols: a 1H and 13C NMR study

The high toxicity of diphenylarsinic acid, found in ground water and well water as a probable consequence of the inappropriate disposal of warfare agents, prompted us to study the reaction, monitored by 1H and 13C NMR spectroscopy, of the compound and its monophenyl analogue, phenylarsonic acid, with cellular thiols as represented, in particular, by glutathione. Glutathione reduced the phenylarsenic acids to trivalent forms and complexed them: diphenylarsinic acid to a monoglutathione adduct and phenylarsonic acid to a diglutathione adduct. The complexes were characterized by 1H and 13C NMR spectroscopy and mass spectrometry. The NMR spectra showed the diastereotopic nature of the two phenyl groups in the diphenylarsinic acid-glutathione compound, and of the two glutathione residues in the phenylarsonic acid-diglutathione complex. The stereochemistry of thiol compounds of phenylarsonic acid was further explored by 1H and 13C NMR spectroscopy of the L-cysteine complex. The diphenylarsinic acid-glutathione complex was stable below pH 12 but at higher pH the complex dissociated into diphenylarsinous acid and reduced glutathione. The released diphenylarsinous acid then oxidized to diphenylarsinic acid with a half-life of about 7 h at pH 13 and at room temperature.     

Bis(ortho-)chelated Monoanionic Bisphosphinoaryl Ruthenium(II) Complexes: Synthesis, Characterization and Reactivity

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｉｎｔｅｒａｃｔｉｏｎｏｆｂｉｓｐｈｏｓｐｈｉｎｅｓｗｉｔｈ (ｔｒａｎｓｉｔｉｏｎ)ｍｅｔａｌｓｉｓａｆａｓｃｉｎａｔｉｎｇｆｉｅｌｄｆｒｏｍｔｈｅｃｏｏｒｄｉｎａｔｉｏｎｃｈｅｍｉｓｔ’ｓｐｏｉｎｔｏｆｖｉｅｗ .Ａｗｉｄｅａｒｒａｙｏｆｍｏｎｏ ａｎｄｍｕｌｔｉ ｍｅｔａｌｌｉｃｃｉｓ η2 Ｐ ,Ｐ′ｃｏｏｒｄｉｎａｔｅｄｃｏｍｐｌｅｘｅｓａｒｅｆｏｒｍｅｄｉｎｗｈｉｃｈａｖａｒｉｅｔｙｏｆｃｏｏｒｄｉｎａｔｉｏｎｍｏｄｅｓｉｓｅｎ ｃｏｕｎｔｅｒｅｄ .Ｔｈｅｃｈｅｌａ…     

Intramolecular cyclization of ortho-(cyclohex-2-enyl) anilines synthesis of ellipticine

A convenient method is proposed for the synthesis of the alkaloid ellipticine, which possesses a pronounced antitumoral activity. The interaction of 3-bromocyclohexene (1 equiv.) and 2,5-xylylidine (4 equiv., 150°C, 5 h) gave a mixture of hexa- and tetrahydrocarbazoles which was dehydrogenated in the presence of Pd/C to the key synthon 1,4-dimethylcarbazole. The formylation of the carbazole by the Vilsmeier-Haack reaction, interaction with 2,2-diethoxyethylamine, and reduction of the imine formed over Raney nickel led to 3-(2,2-diethoxyethylaminomethyl)-1,4-dimethylcarbazole, the boiling of the N-tosylate of which gave ellipticine in high yield. Institute of Organic Chemistry, Urals Branch, Russian Academy of Sciences, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 549–554, September–October, 1992.     

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.     

Substituted phenylarsonic acids; structures and spectroscopy

Full NMR and ESI-MS spectra, and differential scanning calorimeter data are presented for 15 substituted phenylarsonic acids, including two new fluoro-substituted examples. X-ray crystal structure determinations of five examples (phenylarsonic acid and the 4-fluoro-, 4-fluoro-3-nitro-, 3-amino-4-hydroxy- and 3-amino-4-methoxy-substituted derivatives) were determined and the H-bonding crystal-packing patterns analysed.     

Crystal and Molecular Structure of 2,3,5,6- Bis（ortho-1,10-decylidene）dihydropyrazine

1 INTRODUCTION The 1,4-dihydropyrazine ring system has attrac- ted much interest as a structural unit: 1) the possi- bility of cyclic 8π-electron conjugation gives rise to “antiaromatic” character; 2) these ring systems are thus electron rich and readily lose a single electron (namely single electron transfer reaction, SET) to give stable radical cations which are stabilized by captodative effect and/or other factors. Calculations for planar 1,4-dihydropyrazine have predicted the occup…     

Cyclization of ortho-(alk-2-enyl)anilines under the action of iodine

The reaction of ortho-(cyclohex-2-enyl)aniline with I₂ in nonpolar and polar solvents affords predominantly 1-iodohexahydrocarbazole and azatricyclotridecatriene, respectively. Under analogous conditions, 4-methyl-2-(1-methylbut-2-en-1-yl)aniline undergoes cyclization to form exclusively products with quinoline structures regardless of the solvent used.     

Mild and rapid method for the generation of ortho-(naphtho)quinone methide intermediates

A new mild method has been devised for generating o-(naphtho)quinone methides via fluoride-induced desilylation of silyl derivatives of o-hydroxybenzyl(or 1-naphthylmethyl) nitrate. The reactive o-(naphtho)quinone methide intermediates were trapped by C, O, N, and S nucleophiles and underwent "inverse electron-demand" hetero-Diels-Alder reaction with dienophiles to give stable adducts. The method has useful potential application in natural product synthesis and drug research.