Faina Gelman

Field and laboratory studies of the fate and enantiomeric enrichment of venlafaxine and O-desmethylvenlafaxine under aerobic and anaerobic conditions

The stereoselectivity of R,S-venlafaxine and its metabolites R,S-O-desmethylvenlafaxine, N-desmethylvenlafaxine, O,N-didesmethylvenlafaxine, N,N-didesmethylvenlafaxine and tridesmethylvenlafaxine was studied in three processes: (i) anaerobic and aerobic laboratory scale tests; (ii) six wastewater treatment plants (WWTPs) operating under different conditions; and (iii) a variety of wastewater treatments including conventional activated sludge, natural attenuation along a receiving river stream and storage in operational and seasonal reservoirs. In the laboratory and field studies, the degradation of the venlafaxine yielded O-desmethylvenalfaxine as the dominant metabolite under aerobic and anaerobic conditions. Venlafaxine was almost exclusively converted to O-desmethylvenlafaxine under anaerobic conditions, but only a fraction of the drug was transformed to O-desmethylvenlafaxine under aerobic conditions. Degradation of venlafaxine involved only small stereoisomeric selectivity. In contrast, the degradation of O-desmethylvenlafaxine yielded remarkable S to R enrichment under aerobic conditions but none under anaerobic conditions. Determination of venlafaxine and its metabolites in the WWTPs agreed well with the stereoselectivity observed in the laboratory studies. Our results suggest that the levels of the drug and its metabolites and the stereoisomeric enrichment of the metabolite and its parent drug can be used for source tracking and for discrimination between domestic and nondomestic wastewater pollution. This was indeed demonstrated in the investigations carried out at the Jerusalem WWTP.

One-pot sequences of reactions with sol-gel entrapped opposing reagents. Oxidations and catalytic reductions

An oxidant and a reducing catalyst are placed in a single pot without destroying each other, but are still capable of carrying out useful reactions, simultaneously. The oxidant, pyridinium dichromate, and an H2-reduction catalyst, RhCl[P(C6H5)3]3, were entrapped in separate sol-gel matrices, and with these entrapped reagent and catalyst, three different flow-chart sequences of one-pot redox reactions were carried out—up to four reactions in one pot—without their mutual destruction and with no need for separation steps.

Sol–gel entrapped chiral rhodium and ruthenium complexes as recyclable catalysts for the hydrogenation of itaconic acid

Abstract Chiral Ru–BINAP, Rh–DIOP and Rh–BPPM complexes have been physically entrapped in sol–gel matrices. The resulting materials are recyclable leach-proof catalysts for enantioselective hydrogenation of itaconic acid. Chiral methylsuccinic acid of o.p. up to 78% is obtained. The complexes, including the water insoluble Ru–BINAP derivatives, react both in organic and in aqueous media.

One-Pot Reactions with Sol-Gel Entrapped Catalysts, Acids and Bases

Silica sol-gel entrapped acids, bases and organometallic catalysts are used successfully in one-pot reactions without interfering with each other. Both physically and covalently entrapped acids and bases were employed in these processes, including polystyrene sulfonic acid, 1-propane sulfonic acid, molybdosilicic acid (SiO2-MoO3), poly[(vinylbenzyltrimethyl)ammonium] hydroxide and 1,5,7-triazabicyclo[4.4.0]decene. The entrapped metal-based catalysts are Rh2Co2(CO)12 and RuCl2(PPh3)3. The one-pot reactions carried out with these heterogenized reagents and catalysts include formation of alkenes under acidic and basic conditions, C—C bond formation by condensation reactions with an α-carbon to a carbonyl, hydroformylation and hydrogenation.

Chiral and Isotope Analyses for Assessing the Degradation of Organic Contaminants in the Environment: Rayleigh Dependence

The Rayleigh equation is frequently used to describe isotope fractionation as a function of conversion. In this article we propose to draw a parallel between isotope and enantiomeric enrichments and derive a set of conditions that allow the use of the Rayleigh approach to describe the enantiomeric enrichment-conversion dependencies. We demonstrate an implementation of the Rayleigh equation for the enantioselective enzymatic hydrolysis of Mecoprop-methyl, Dichlorprop-methyl, and dimethyl-methylsuccinate by lipases from Pseudomonas fluorescens, Pseudomonas cepacia, and Candida rugosa. The data obtained for all the studied reactions gave good fits to the Rayleigh equation, with a linear regression R(2) > 0.96. In addition to that, our analysis of four microcosm studies on the hydrolysis of the individual enantiomers of Dichloroprop methyl, Lactofen, Fenoxaprop-ethyl, and Metalaxyl reported in the literature by other research groups revealed a suitability of the Rayleigh dependence. Two dimensional plots describing the isotope fractionation versus enantiomeric enrichment are demonstrated for all studied cases. Processes not accompanied by enantiomeric enrichment (acid and base hydrolysis) and by isotope enrichment (transesterification) are demonstrated, their 2-D plots are either horizontal or vertical which can illuminate concealed degradation pathways.

Hydrogenation and dehalogenation of aryl chlorides and fluorides by the sol–gel entrapped RhCl3–Aliquat 336 ion pair catalyst

Abstract The SiO 2 sol–gel entrapped ion pair [(C 8 H 17 ) 3 NMe] + [RhCl 4 . n H 2 O] − , generated from RCl 3 . 3H 2 O, Aliquat 336® and Si(OMe) 4 catalyzes at 80°C and 16 atm. H 2 , the hydrogenation of aryl fluorides and chlorides to give halogen-free hydroaromatics. Fluorobenzenes initially yield fluorocyclohexanes which eliminate HF, in a non-catalytic process, followed by hydrogenation of the cyclohexenes. In contrast, chlorobenzenes are first dehalogenated to the corresponding benzene derivatives, that in a second step are hydrogenated to cyclohexanes. Aryl bromides undergo dehalogenation and hydrogenation as well, but only in the presence of a free radical scavenger. The catalyst in these reactions is leach-proof and recyclable with little or no loss in activity.

Sol–gel entrapped heteronuclear transition metal catalysts

Abstract The heteronuclear complexes [(CO)4Fe(μ-PPh2)Pd(μ-Cl)2]2, [Et4N][FeCo3(CO)12] and Rh2Co2(CO)12 were physically entrapped in SiO2–sol–gel matrices. The doped materials, so formed, were utilized as recyclable catalysts for (a) selective isomerization of 1-octene, (b) selective dimerization of norbornadiene to ‘binor-S’, and (c) hydrogenation and hydrogenolysis of styrene, nitrobenzene and 1-chloronaphthalene, respectively. During the hydrogenation of the nitrobenzene and of chloronaphthalene, the dodecacarbonylbis(cobalt)dirhodium was converted into sol–gel entrapped carbonyl-free nanoparticles that efficiently catalyze the reduction of the aromatic C–C bonds.

Kinetic bromine isotope effect: example from the microbial debromination of brominated phenols.

The increasing use of kinetic isotope effects for environmental studies has motivated the development of new compound-specific isotope analysis techniques for emerging pollutants. Recently, high-precision bromine isotope analysis in individual brominated organic compounds was proposed, by the coupling of gas chromatography to a multi-collector inductively coupled plasma mass spectrometer using strontium as an external spike for instrumental bias correction. The present study, for the first time, demonstrates an application of this technique for determining bromine kinetic isotope effects during biological reaction, focusing on the reductive debromination of brominated phenols under anaerobic conditions. Results show bromine isotope enrichment factors (ε) of −0.76 ± 0.08, −0.46 ± 0.19, and −0.20 ± 0.06 ‰ for the debromination of 4-bromophenol, 2,4-dibromophenol, and 2,4,6-tribromophenol, respectively. These values are rather low, yet still high enough to be obtained with satisfying certainty. This further implies that the analytical method may be also appropriate for future environmental applications.

SYNTHESIS, IMMOBILIZATION AND CATALYTIC ACTIVITY OF SOME SILYLATED CYCLOPENTADIENYL RHODIUM(I) COMPLEXES

The mixture of isomers of silylated cyclopentadiene derivative C5H5CH2CH2Si(OMe)3 (1) has been used for the syntheses of the mononuclear Rh(I) complexes [η5-C5H4(CH2)2Si(OMe)3]Rh(CO)2 (3). [η5-C5H4(CH2)2Si(OMe)3]Rh(COD) (4) and [η5-C5H4(CH2)2Si(OMe)3]Rh(CO)(PPh3) (5). Upon entrapment of 3–5 in silica sol-gel matrices, air stable, leach-proof and recyclable catalysts 6–8 resulted. Their catalytic activities in some hydrogenation processes were compared with those of the non-immobilized complexes 3–5, as well as with those of homogeneous and heterogenized non-silylated analogs, 9–14.

Application of dual carbon-bromine isotope analysis for investigating abiotic transformations of tribromoneopentyl alcohol (TBNPA).

Many of polybrominated organic compounds, used as flame retardant additives, belong to the group of persistent organic pollutants. Compound-specific isotope analysis is one of the potential analytical tools for investigating their fate in the environment. However, the isotope effects associated with transformations of brominated organic compounds are still poorly explored. In the present study, we investigated carbon and bromine isotope fractionation during degradation of tribromoneopentyl alcohol (TBNPA), one of the widely used flame retardant additives, in three different chemical processes: transformation in aqueous alkaline solution (pH 8); reductive dehalogenation by zero-valent iron nanoparticles (nZVI) in anoxic conditions; oxidative degradation by H2O2 in the presence of CuO nanoparticles (nCuO). Two-dimensional carbon-bromine isotope plots (δ(13)C/Δ(81)Br) for each reaction gave different process-dependent isotope slopes (Λ(C/Br)): 25.2 ± 2.5 for alkaline hydrolysis (pH 8); 3.8 ± 0.5 for debromination in the presence of nZVI in anoxic conditions; ∞ in the case of catalytic oxidation by H2O2 with nCuO. The obtained isotope effects for both elements were generally in agreement with the values expected for the suggested reaction mechanisms. The results of the present study support further applications of dual carbon-bromine isotope analysis as a tool for identification of reaction pathway during transformations of brominated organic compounds in the environment.