Nanofiltration process of glyphosate simulated wastewater

Nanofiltration separation of glyphosate simulated wastewater was investigated using a DK membrane. The effects of operating parameters and the addition of impurities on membrane performance were studied in detail. It was found that at 20 °C, with a glyphosate concentration of 500 mg/L and pH of 2.96, the glyphosate retention rate and the membrane permeate flux increased slightly with increasing transmembrane pressure. With an increase in operating temperature, the permeate flux increased linearly while the retention rate decreased. The permeate flux and glyphosate retention rate decreased with increasing feed concentration. Within the pH range of 3-5, the glyphosate retention rate decreases with increasing pH and reaches a minimum at the isoelectric point of the membrane, while the permeate flux reaches a maximum level at this point. In the pH range of 5-11, with the increases of pH, the glyphosate retention rate increases and the permeate flux decreases. Glyphosate retention decreases slightly with increasing NaCl and phosphite concentrations. This can be explained in terms of the shielding phenomenon.

Dry autoclaving for the nanofabrication of sulfides, selenides, borides, phosphides, nitrides, carbides, and oxides

This review compiles various nanostructures fabricated by a distinct "dry autoclaving" approach, where the chemical reactions are carried out without solvents; above the dissociation temperature of the chemical precursor(s) at elevated temperature in a closed reactor. The diversity to fabricate carbides (SiC, Mo(2) C, WC), oxides (VOx-C, ZnO, Eu(2) O(3) , Fe(3) O(4) , MoO(2) ), hexaborides (LaB(6) , CeB(6) , NdB(6) , SmB(6) , EuB(6) , GdB(6) ), nitrides (TiN, NbN, TaN), phosphides (PtP(2) , WP), sulfides (ZnS, FeS/C, SnS/C, WS(2) , WS(2) /C), and selenides (Zn(1-x) Mn(x) Se/C, Cd(1-x) Mn(x) Se/C), with various shapes and sizes is accounted with plausible applications. This unique single-step, solvent-free synthetic process opens up a new route in the growing nanomaterials science; owing to its considerable advantages on the existing approaches.

Dinucleotides containing 3'-S-phosphorothiolate linkages

The 3'-S-phosphorothiolate (3'-SP) linkage has proven to be a very useful analogue of the phosphodiester group in nucleic acid derivatives; it is achiral and also shows good resistance to nucleases. Whilst oligonucleotides containing a 3'-SP linkage are best prepared using phosphoramidite chemistry, the corresponding dinucleotides are most efficiently synthesised using a Michaelis-Arbuzov reaction between a nucleoside 5'-phosphite and a nucleoside 3'-S-disulphide. The method described here is for a thymidine dinucleotide and is based on the use of a silyl phosphite, which is more reactive than simple alkyl phosphites and also simplifies the deprotection strategy. Full experimental details and spectroscopic data for the synthetic intermediates and the target dinucleotide are provided.

Organic secondary ion mass spectrometry: signal enhancement by water vapor injection

The enhancement of the static secondary ion mass spectrometry (SIMS) signals resulting from the injection, closely to the sample surface, of H(2)O vapor at relatively high-pressure, was investigated for a set of organic materials. While the ion signals are generally improved with increasing H(2)O pressure upon 12 keV Ga(+) bombardment, a specific enhancement of the protonated ion intensity is clearly demonstrated in each case. For instance, the presence of H(2)O vapor induces an enhancement by one order of magnitude of the [M + H](+) static SIMS intensity for the antioxidant Irgafos 168 and a ∼1.5-fold increase for polymers such as poly(vinyl pyrrolidone).

A highly efficient bismuth salts-catalyzed route for the synthesis of α-aminophosphonates

A convenient synthesis of different types of α-amino phosphonates via one-pot solvent-free three component reactions of aldehydes, amines and phosphites catalyzed by bismuth salts has been investigated. Bismuth triflate is found to be the most effective catalyst for this reaction.

Application of phosphine-phosphite ligands in the iridium catalyzed enantioselective hydrogenation of 2-methylquinoline

The hydrogenation of 2-methylquinoline with Ir catalysts based on chiral phosphine-phosphites has been investigated. It has been observed that the reaction is very sensitive to the nature of the ligand. Optimization of the catalyst, allowed by the highly modular structure of these phosphine-phosphites, has improved the enantioselectivity of the reaction up to 73% ee. The influence of additives in this reaction has also been investigated. Contrary to the beneficial influence observed in related catalytic systems, iodine has a deleterious effect in the present case. Otherwise, aryl phosphoric acids produce a positive impact on catalyst activity without a decrease on enantioselectivity.

Asymmetric hydrophosphylation of chiral N-phosphonyl imines provides an efficient approach to chiral α-amino phosphonates

Chiral N-phosphonylimines were found to react with lithium phosphites to provide various substituted chiral α-amino phosphonates in excellent yields (94-97%) and diastereoselectivities (93:7-99:1). The types of bases utilized for generating the nucleophile are crucial for the effectiveness of asymmetric induction. In addition, N,N-isopropyl group on chiral N-phosphonylimine auxilliary was proven to be superior to other protecting groups in controlling diastereoselectivity. The absolute configuration was unambiguously determined by converting a chiral α-amino phosphonate into its authentic N-Cbz derivative.

Synthesis and structure-activity relationship analysis of bicyclophosphorothionate blockers with selectivity for housefly gamma-aminobutyric acid receptor channels

BACKGROUND

Bicyclophosphorothionates (2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane-1-sulfides) are blockers (or non-competitive antagonists) of gamma-aminobutyric acid (GABA) receptor channels. Twenty-two bicyclophosphorothionates with different 3- and 4-substituents were synthesised, and [(3)H]4'-ethynyl-4-n-propylbicycloorthobenzoate (EBOB) binding assays were performed to evaluate their affinities for housefly and rat GABA receptors.

RESULTS

Introduction of an isopropyl group at the 3-position enhanced the affinity of bicyclophosphorothionates for housefly GABA receptors and reduced the affinity towards rat GABA receptors. The 4-isopentyl-3-isopropylbicyclophosphorothionate showed the highest affinity for housefly GABA receptors (IC(50) = 103 nM) among the analogues tested, while the 4-cyclohexylbicyclophosphorothionate showed the highest affinity for rat GABA receptors (IC(50) = 125 nM). Among the bicyclophosphorothionates synthesised to date, the former analogue exhibited the highest selectivity for housefly GABA receptors, with an IC(50)(rat)/IC(50)(fly) ratio of approximately 97. Three-dimensional GABA receptor models successfully explained the structure-activity relationships of the bicyclophosphorothionates.

CONCLUSION

The results indicate that minor structural modifications of blockers can change their selectivity for insect versus mammalian GABA receptors. The substituent at the 3-position of the bicyclophosphorothionates dictates selectivity for housefly versus rat GABA receptors. This information should prove useful for the design of safer insecticides and parasiticides.

Plasma chemical degradation of phosphorous-containing warfare agents simulants

The gliding electric discharge (or "glidarc") technique is a new advanced oxidation process used for the degradation of organic solutes or spent solvents. Discharges in humid air at atmospheric pressure produce active species (i.e., .OH and .NO) that are able to oxidize organic target up to carbon oxides and water. Aqueous solutions of triethylphosphate (TEP), a warfare agent simulant, are exposed to a glidarc in humid air to evaluate the solute stability under the impinging flux of active species. TEP was degraded and the overall zero order kinetic rate (k(0)=3.4 x 10(-4)mol h(-1)) was compared with that of previously considered tributylphosphate. The total degradation of TEP is monitored by the formation of H(3)PO(4) as the ultimate oxidation product of phosphorus by total organic carbon measurements. Extra investigation was performed on dimethylmethylphosphonate to examine the potential influence of the molecule symmetry on the degradation rate.

Removal of citrate and hypophosphite binary components using Fenton, photo-Fenton and electro-Fenton processes

Both citrate and hypophosphite in aqueous solution were degraded by advanced oxidation processes (Fe2+/H2O2, UV/Fe2+/H2O2, and electrolysis/ Fe2+/H2O2) in this study. Comparison of these techniques in oxidation efficiency was undertaken. It was found that Fenton process could not completely degrade citrate in the presence of hypophosphite since it caused a series inhibition. Therefore, UV light (photo-Fenton) or electron current (electro-Fenton) was applied to improve the degradation efficiency of the Fenton process. Results showed that both photo-Fenton and electro-Fenton processes could overcome the inhibition of hypophosphite, especially the electro-Fenton.

Carbohydrate-derived 1,3-diphosphite ligands as chiral nanoparticle stabilizers: promising catalytic systems for asymmetric hydrogenation

Metallic Ru, Rh, and Ir nanoparticles were prepared by the decomposition of organometallic precursors under H(2) pressure in the presence of 1,3-diphosphite ligands, derived from carbohydrates, as stabilizing agents. Structural modifications to the diphosphite backbone were found to influence the nanoparticles' size, dispersion, and catalytic activity. In the hydrogenation of o- and m-methylanisole, the Rh nanoparticles showed higher catalytic activity than the corresponding Ru nanoparticles. The Ir nanoparticles presented the lowest catalytic activity of the series. In all cases, the hydrogenation of o-methylanisole gave total selectivity for the cis-product, however, the ee of the product was always less than 6 %. A maximum of 81 % cis-selectivity was obtained for the hydrogenation of m-methylanisole, however, no asymmetric induction was observed. These results show that the catalytic activity is affected by a combination of influences from the substrate, the diphosphite ligands, and the metallic nanoparticles.

A surprising mechanistic "switch" in Lewis acid activation: a bifunctional, asymmetric approach to alpha-hydroxy acid derivatives

We report a detailed synthetic and mechanistic study of an unusual bifunctional, sequential hetero-Diels-Alder/ring-opening reaction in which chiral, metal complexed ketene enolates react with o-quinones to afford highly enantioenriched, alpha-hydroxylated carbonyl derivatives in excellent yield. A number of Lewis acids were screened in tandem with cinchona alkaloid derivatives; surprisingly, trans-(Ph(3)P)(2)PdCl(2) was found to afford the most dramatic increase in yield and rate of reaction. A series of Lewis acid binding motifs were explored through molecular modeling, as well as IR, UV, and NMR spectroscopy. Our observations document a fundamental mechanistic "switch", namely the formation of a tandem Lewis base/Lewis acid activated metal enolate in preference to a metal-coordinated quinone species (as observed in other reactions of o-quinone derivatives). This new method was applied to the syntheses of several pharmaceutical targets, each of which was obtained in high yield and enantioselectivity.

Water solubilization of DDGS via derivatization with phosphite esters

Ethanol production from corn starch in the corn dry milling process leaves Distillers' Dry Grains and Solubles (DDGS) as a major by-product from which additional ethanol may be economically obtained from its glucan content. A challenge in processing the cellulose content of this material lies in its extensive inter-cellulose chain hydrogen bonding, which inhibits access of enzymes capable of cleaving glycosidic bonds, a transformation required for providing fermentable sugars. The phosphitylation of cellulosic OH groups using a reactive bicyclic phosphite ester is utilized to disrupt cellulosic hydrogen bonds, thus providing access to cellulose chains for further processing. We describe a method of pretreating DDGS with commercially available trimethylolpropane phosphite [P(OCH2)3CEt] in the presence of a slight molar excess of water to afford greater than 90% DDGS solubility in the reaction mixture in methanol and in water. Preliminary results using a model compound [D-(+)-permethylated cellobiose] indicate that glycosidic bonds are cleaved as a consequence of this pretreatment.

An improved method for de novo sequencing of arginine-containing, Nalpha-tris(2,4,6-trimethoxyphenyl)phosphonium-acetylated peptides

An improved method for de novo sequencing of arginine-containing peptides modified with succinimidyloxycarbonylmethyl tris(2,4,6-trimethoxyphenyl)phosphonium bromide (TMPP-Ac-OSu) is reported. A tagging reagent, TMPP-Ac-OSu, was introduced to improve the sequence analysis of peptides owing to the simplified fragmentation pattern. However, peptides containing arginine residues did not fragment efficiently even after TMPP-Ac modification at their N-termini. This report describes how fragmentation efficiency of TMPP-Ac-modified arginine-containing peptides was significantly improved by modifying the guanidino group on the side chain of arginine with acetylacetone.

The reaction of mixtures of [Rh4(CO)12] and triphenylphosphite with carbon monoxide or syngas as studied by high-resolution, high-pressure NMR spectroscopy

The fragmentation and redistribution reactions of [Rh4(CO)12-x{P(OPh)3}x] (x = 1-4) with carbon monoxide have been studied using high-resolution, high-pressure NMR spectroscopy. Under the conditions of efficient gas mixing in a high-pressure NMR bubble column, [Rh4(CO)9{P(OPh)3}3] fragments to give mainly [Rh2(CO)6{P(OPh)3}2]; [Rh4(CO)11{P(OPh)3}] is also observed,implying redistribution of the phosphite ligand and/or recombination of the dimers to tetrameric clusters. Fragmentation of[Rh4(CO)10{P(OPh)3}2] is found to be pressure-dependent giving predominantly [Rh2(CO)6{P(OPh)3}2] at low CO pressure (1-40 bar), and increasing amounts of [Rh2(CO)7{P(OPh)3}] at higher (40-80 bar) pressure. Using Syngas (CO : H2 (1 : 1)) instead of CO in the above fragmentations, homolytic addition of H2 to the dimer [Rh2(CO)6{P(OPh)3}2] to give [RhH(CO)3{P(OPh3}] and [RhH(CO)2{P(OPh)3}2] is observed. The distribution of tetrameric species obtained is similar to that obtained under the same partial pressure of CO. On depressurisation/out-gassing of the sample, the original mixture of tetrameric clusters is obtained.

17O NMR investigation of phosphite hydrolysis mechanisms

The use of solution 17O NMR spectroscopy in verifying the mechanism of trialkyl phosphite hydrolysis is presented. Trimethyl phosphite was reacted with 17O-labeled H2O at different temperatures and two reactant concentrations, with the reaction being monitored by 17O NMR. Kinetic details elucidated from the NMR spectra are also discussed.

Stereochemical Features Making Deoxycholic Acid Derived tropos Biphenylphosphites Efficient Chiral Ligands for Rhodium: The Asymmetric Hydrogenation of Dimethylitaconate as a Case Study

Different deoxycholic acid derived biphenylphosphites, whose tropos nature was ascertained by NMR and CD measurements, were used in the rhodium-catalyzed asymmetric hydrogenation of dimethylitaconate achieving enantiomeric excesses up to 91%. The comparison of these results to those obtained using the corresponding atropoisomeric binaphthyl analogues, together with NMR and CD measurements on the rhodium complexes of some phosphites, allowed us to shed light on the nature of the active catalytic species and on the asymmetric induction process and hence to recognize the most appropriate stereochemical features to reach good levels of enantioselectivity.

P-chiral oligonucleotides in biological recognition processes

Internucleotide phosphodiester linkages in non-modified oligonucleotides are quickly degraded by nucleolytic enzymes present in the cells and this feature practically eliminates natural DNA and RNA molecules from medical applications and from many structural and mechanistic studies. P-chiral oligonucleotide analogs, in which one of the non-bridging phosphate oxygen atoms is substituted with another heteroatom (e.g. S, Se) or a chemical group (e.g. CH3, BH3(-)), have significantly greater nuclease resistance and also offer important possibilities for detailed studies of interactions with other biomolecules at the molecular level. Notably, these substitutions do not disrupt hydrogen bonding between nucleobases and affect the overall geometry of the oligomers to only low or moderate extent, although important changes of hydration patterns and changes of interactions with metal ions are observed. Such the probes, including isotopomeric species labeled with a heavy oxygen isotope, possessing phosphorus atoms of selected absolute configurations, have been used for elucidation of the mode of action of many enzymes (nucleases, transferases, kinases), ribozymes and DNA-zymes, as well as for investigations on thermodynamic stability of nucleic acids complexes (duplexes, triplexes, i-motif) and for studies on a mechanism of conformational changes of B-Z type. They are also useful tools for analysis of interactions of the phosphoryl oxygen atoms in natural precursors with functional groups of proteins. The synthetic routes to stereodefined forms of selected types of P-chiral oligonucleotides are presented, as well as recently developed methods for their configurational analysis at micromolar concentration. Selected examples of application of diastereomerically pure P-chiral oligonucleotides for structural, biochemical and biological experiments are discussed.

Tautomerism and hydrogen bonding in guaninium phosphite and guaninium phosphate salts

The crystal structures of three similar guaninium salts, guaninium monohydrogenphosphite monohydrate, C5H6N5O+·H2O3P−·H2O, guaninium monohydrogenphosphite dihydrate, C5H6N5O+·H2O3P−·2H2O, and guaninium dihydrogenmonophosphate monohydrate, C5H6N5O+·H2O4P−·H2O, are described and compared. The crystal structures have been determined from accurate single-crystal X-ray data sets collected at 100 (2) K. The two phosphite salts are monoclinic, space group P21/c, with different packing and the monophosphate salt is also monoclinic, space group P21/n. An investigation of the hydrogen-bond network in these guaninium salts reveals the existence of two ketoamine tautomers, the N9H form and an N7H form.

AgOTf-Catalyzed Three-Component Reactions of 2-Alkynylbenzaldehydes, Amines, and Diethylphosphite. An Efficient Route to 2,3-Disubstituted-1,2-dihydroisoquinolin-1-ylphosphonates

AgOTf was discovered as a highly efficient catalyst in reactions of 2-alkynylbenzaldehydes, amines, and diethylphosphite, which provided a facile and efficient pathway for the synthesis of 2,3-disubstituted-1,2-dihydroisoquinolin-1-ylphosphonates.

Synthesis of solution-phase phosphoramidite and phosphite ligand libraries and their in situ screening in the rhodium-catalyzed asymmetric addition of arylboronic acids

Herein, we report the automated parallel synthesis of solution-phase libraries of phosphoramidite ligands for the development of enantioselective catalysts. The ligand libraries are screened in situ in the asymmetric rhodium-catalyzed addition of arylboronic acids to aldehydes and imines. It is shown that the described methodology results in the straightforward discovery of leads for highly efficient enantioselective catalysts.

Ambient temperature synthesis of high enantiopurity N-protected peptidyl ketones by peptidyl thiol ester-boronic acid cross-coupling

alpha-Amino acid thiol esters derived from N-protected mono-, di-, and tripeptides couple with aryl, pi-electron-rich heteroaryl, or alkenyl boronic acids in the presence of stoichiometric Cu(I) thiophene-2-carboxylate and catalytic Pd(2)(dba)(3)/triethylphosphite to generate the corresponding N-protected peptidyl ketones in good-to-excellent yields and in high enantiopurity. Triethylphosphite plays a key role as a supporting ligand by mitigating an undesired palladium-catalyzed decarbonylation-beta-elimination of the alpha-amino thiol esters. The peptidyl ketone synthesis proceeds at room temperature under nonbasic conditions and demonstrates a high tolerance to functionality.

Feasibility study for the development of certified reference materials for specific migration testing. Part 2: Estimation of diffusion parameters and comparison of experimental and predicted data

This paper describes the second part of a project whose main objective was to develop the know-how to produce certified reference materials (CRMs) for specific migration testing. Certification parameters discussed are the diffusion coefficient, D(P), the respective polymer-specific coefficient, A(P), of the migrant polymer combinations and the partitioning coefficient, K(P,F), describing the partitioning of the migrant between the polymer and a food simulant. The parameters were determined for 16 preliminary candidate CRMs. Each parameter was determined by one laboratory. The six materials most suitable as reference materials were selected and the parameters then determined by four laboratories. The coefficients resulting from this small-scale interlaboratory comparison study can be regarded as the most reliable values available to date. These coefficients were applied for a comparison of experimental and predicted migration data. The experimental migration data arose from the same project and were determined by one laboratory for the first 16 materials and subsequently by four laboratories for the six materials selected in the second phase. Overall, experimental and predicted migration data fit together quite well. Roughly half of the predicted data were within +/-10%; almost all predicted data were within +/-40% compared with the experimental data.

Mechanism of the sulfurisation of phosphines and phosphites using 3-amino-1,2,4-dithiazole-5-thione (xanthane hydride)

Contrary to a previous report, the sulfurisation of phosphorus(III) derivatives by 3-amino-1,2,4-dithiazole-5-thione (xanthane hydride) does not yield carbon disulfide and cyanamide as the additional reaction products. The reaction of xanthane hydride with triphenyl phosphine or trimethyl phosphite yields triphenyl phosphine sulfide or trimethyl thiophosphate, respectively, and thiocarbamoyl isothiocyanate which has been trapped with nucleophiles. The reaction pathway involves initial nucleophilic attack of the phosphorus at sulfur next to the thiocarbonyl group of xanthane hydride followed by decomposition of the phosphonium intermediate formed to products. The Hammett rho-values for the sulfurisation of substituted triphenyl phosphines and triphenyl phosphites in acetonitrile are approximately -1.0. The entropies of activation are very negative (-114+/-15 J mol-1 K-1) with little dependence on solvent which is consistent with a bimolecular association step leading to the transition state. The negative values of DeltaS(not equal) and rho values indicate that the rate limiting step of the sulfurisation reaction is formation of the phosphonium ion intermediate which has an early transition state with little covalent bond formation. The site of nucleophilic attack has been also confirmed using computational calculations.