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A series of polysulfone (PSF) membranes were prepared using different solvents: dimethylformamide (DMF), tetrahydrofuran, dimethylacetamide, and n-methyl-2-pyrrolidone (NMP). The PSF membrane prepared by NMP showed the highest gas permeability. The influence of propionic acid as a Lewis acid on gas separation properties of the PSF was explored. The PSF membrane prepared by the casting solution containing 25 wt% PSF, 35 wt% propionic acid, and 40 wt% NMP showed a superior gas separation performance. The gas permeation measurements indicated that incorporating 30 wt % [gamma]-alumina nanoparticles into the PSF matrix resulted in about the respective 43% and 41% increase in C[O.sub.2] and [O.sub.2] permeability together with a rise in C[O.sub.2]/ C[H.sub.4] and [O.sub.2]/[N.sub.2] selectivities (13% and 7%, respectively). Furthermore, by rearranged modified Maxwell model, the role and nature of the interfacial layer in the PSF-based mixed matrix membranes were mathematically analyzed considering a reduced permeability factor. KEYWORDS gas separation, Lewis acid-base complex, mixed matrix membranes, polysulfone membranes, solvent effect, 1 | INTRODUCTION Global warming due to C[O.sub.2] emission into the atmosphere, and production of clean and conventional energies ([H.sub.2] and C[H.sub.4], respectively) has attracted great attention to the need [...]

Acetaldehyde is one of the well-known undesirable by-product formed during different stages of polyethylene terephthalate manufacturing process. The migration of acetaldehyde from polyethylene terephthalate, even at trace levels of 10-25 ppb is known to adversely impact organoleptic property of water and/or beverages. We are reporting for the first time in-situ formation of acetaldehyde in polyethylene terephthalate pellets due to the presence of residual levels of 2-methyl 1, 3-dioxolane in the final polymer. A new insight on generation of acetaldehyde through hydrolysis of 2-methyl 1, 3-dioxolane present in polyethylene terephthalate resin has been established through water spiking studies in a controlled environment. Further, systematic studies were conducted to also understand the mechanism of formation of 2-methyl 1, 3-dioxolane during the polyethylene terephthalate manufacturing. KEYWORDS 2-methyl 1, 3-dioxolane, acetaldehyde, bis (2-hydroxyethyl) terephthalate), mono ethylene glycol, polyethylene terephthalate, terephthalic acid, 1 | INTRODUCTION Poly(ethylene terephthalate) (PET) resin, which is semi crystalline in nature, belongs to the family of polyesters. Due to its inert, transparent, lightweight and unbreakable characteristics, it has [...]

Reactions of the aryl complexes Rh[(aryl){[K.sup.3]-P,O,P-[xant([P.sup.i][Pr.sub.2]).sub.2]]} (1; aryl = 3,5-[Me.sub.2][C.sub.6][H.sub.3] (a), [C.sub.6][H.sub.5] (b), 3,5-[Cl.sub.2][C.sub.6][H.sub.3] (c), 3-[FC.sub.6][H.sub.4] (d); xant[([P.sup.i][Pr.sub.2]).sub.2] = 9,9-dimethyl-4,5-bis-(diisopropylphosphino)xanthene) with [O.sub.2], CO, and [MeO.sub.2]CC=[CCO.sub.2]Me have been performed. Under 1 atm of [O.sub.2], the pentane solutions of complexes 1 afford the dinuclear peroxide derivatives [[Rh[(aryl){[K.sup.2]-P,P-xant([P.sup.i][Pr.sub.2]).sub.2]}].sub.2][([micro]-[O.sub.2]).sub.2] (2a-2d) as yellow solids. In solution, these species are unstable. In dichloromethane, at room temperature, they are transformed into the dioxygen adducts Rh[(aryl)([[eta].sup.2]-[O.sub.2]){[K.sup.3]-P,O,P-[xant([P.sup.i][Pr.sub.2]]).sub.2]]} (3a-3d), as a result of the rupture of the double peroxide bridge and the reduction of the metal center. Complex 3b decomposes in benzene, at 50 [degrees]C, to give diphosphine oxide, phenol, and biphenyl. Complexes 1 react with CO to give the square-planar mono carbonyl derivatives Rh[(aryl)(CO){[K.sup.2]-P,P-[xant([P.sup.i][Pr.sub.2]).sub.2]]} (4a-4d), which under carbon monoxide atmosphere evolve to benzoyl species Rh{C[(O)aryl}(CO){[K.sup.2]-P,P-[xant([P.sup.i][Pr.sub.2]).sub.2]]} (5a-5d), resulting from the migratory insertion of CO into the Rh-arylbond and the coordination of a second CO molecule. The transformation is reversible; under vacuum, complexes 5 regenerate the precursors 4. The addition of the activated alkyne to complexes 1b and 1d initially leads to the 7T-alkyne intermediates Rh[(aryl){[[eta].sup.2]-C([CO.sub.2]Me[equivalent to]C([CO.sub.2]Me)}{[K.sup.3]-P,O,P-[xant([P.sup.i][Pr.sub.2]]).sub.2]]} (6b, 6d), which evolve to the alkenyl derivatives Rh{[(E)-C([CO.sub.2]Me)=C([CO.sub.2]Me)aryl}{[K.sup.3]-P,O,P-[xant([P.sup.i][Pr.sub.2]).sub.2]]} (7b, 7d). The diphosphine adapts its coordination mode to the stability requirements of the different complexes, coordinating cis-[K.sup.2]-P,P in complexes 2, fac -[[kappa].sup.3]-P,O,P in compounds 3, trans-[K.sup.2]-P,P in the mono carbonyl derivatives 4 and 5, and mer-[[kappa].sup.3]-P,O,P in products 6 and 7. Key words: rhodium, pincer ligand, peroxide, carbonyl, aryl. Nous avons fait reagir les complexes aryliques Rh[(aryl){[K.sup.3]-P,O,P-[xant([P.sup.i][Pr.sub.2]).sub.2]]} (1; aryl = 3,5-[Me.sub.2][C.sub.6][H.sub.3] (a), [C.sub.6][H.sub.5] (b), 3,5-[Cl.sub.2][C.sub.6][H.sub.3] (c), 3-[FC.sub.6][H.sub.4] [(d); xant([PPr.sub.2]).sub.2] = 9,9-dimethyl-4,5-bis-(diisopropylphosphino)xanthene) avec l'[O.sub.2], le CO et le [MeO.sub.2]CC=[CCO.sub.2]Me. Sous 1 atm d'[O.sub.2], les solutions des complexes 1 dans le pentane ont produit les derives de peroxyde dinucleaires [[Rh[(aryl){[K.sup.2]-P,P-xant([P.sup.i][Pr.sub.2]).sub.2]}].sub.2][([micro]-[O.sub.2]).sub.2] (2a-2d). Ces especes, qui se presentent sous forme de solide jaune, se sont revelees instables en solution. Dans le dichloromethane a temperature ambiante, elles ont forme les adduits de dioxygene Rh[[(aryl)(T).sup.2]-[O.sub.2]){[K.sup.3]-P,O,P-[xant([P.sup.i][Pr.sub.2]).sub.2]]} (3a-3d) apres rupture du double pont peroxyde et reduction du centre metallique. Le complexe 3b se decompose dans le benzene a 50 [degrees]C en oxyde de diphosphine, en phenol et en biphenyle. Les complexes 1 reagissent avec le CO pour produire les derives monocarbonyles de structure plan carre Rh[(aryl)(CO){[K.sup.2]-P,P-[xant([P.sup.i][Pr.sub.2]).sub.2]]} (4a-4d), qui, sous atmosphere de monoxyde de carbone, se transforment en especes benzoyle Rh{C[(O)aryl}(CO){[K.sup.2]-P,P-[xant([P.sup.i][Pr.sub.2]).sub.2]]} (5a-5d) a la suite de l'insertion migratoire du CO dans la liaison Rh-aryl et de la coordination d'une seconde molecule de CO. Cette transformation est reversible : sous vide, les complexes 5 regenerent les precurseurs 4. L'addition de l'alcyne active aux complexes 1b et 1d produit initialement les intermediaires [pi]-alcyne Rh(aryl){[[eta].sup.2]-C([CO.sub.2]Me[equivalent to] C[([CO.sub.2]Me)}{[[kappa].sup.3]-P,O,P-[xant([P.sup.i][Pr.sub.2]]).sub.2]]} (6b, 6d), qui se transforment par la suite en derives alcenyle Rh{(E)-C([CO.sub.2]Me)=C([CO.sub.2]Me)aryl} {[K.sup.3]-P,O,P-[xant[([P.sup.i][Pr.sub.2]).sub.2]]} (7b, 7d). Le ligand diphosphine adapte son mode de coordination aux contraintes de stabilite des differents complexes, se coordonnant en mode cis-[K.sup.2]-P,P dans les complexes 2, en modefac-[K.sup.3]-P,O,P dans les composes 3, en mode trans-[K.sup.2]-P,P dans les derivees monocarbonyles 4 et 5, et en mode mer-[K.sup.3]-P,O,P dans les produits 6 et 7. [Traduit par la Redaction] Mots-cles: rhodium, ligand pince, peroxide, carbonyle, aryle., Introduction Square-planar rhodium(I) aryl complexes of general formula [L.sub.3]Rh-aryl are stabilized with three phosphines, (1) bulky carbenes, (2) or bulky substituents at the ortho positions of the coordinated aryl group. [...]

The oxygen evolution reaction has an important role in many alternative-energy schemes because it supplies the protons and electrons required for converting renewable electricity into chemical fuels.sup.1-3. Electrocatalysts accelerate the reaction by facilitating the required electron transfer.sup.4, as well as the formation and rupture of chemical bonds.sup.5. This involvement in fundamentally different processes results in complex electrochemical kinetics that can be challenging to understand and control, and that typically depends exponentially on overpotential.sup.1,2,6,7. Such behaviour emerges when the applied bias drives the reaction in line with the phenomenological Butler-Volmer theory, which focuses on electron transfer.sup.8, enabling the use of Tafel analysis to gain mechanistic insight under quasi-equilibrium.sup.9-11 or steady-state assumptions.sup.12. However, the charging of catalyst surfaces under bias also affects bond formation and rupture.sup.13-15, the effect of which on the electrocatalytic rate is not accounted for by the phenomenological Tafel analysis.sup.8 and is often unknown. Here we report pulse voltammetry and operando X-ray absorption spectroscopy measurements on iridium oxide to show that the applied bias does not act directly on the reaction coordinate, but affects the electrocatalytically generated current through charge accumulation in the catalyst. We find that the activation free energy decreases linearly with the amount of oxidative charge stored, and show that this relationship underlies electrocatalytic performance and can be evaluated using measurement and computation. We anticipate that these findings and our methodology will help to better understand other electrocatalytic materials and design systems with improved performance. Spectroscopic studies and theoretical calculations of the electrocatalytic oxygen evolution reaction establish that reaction rates depend on the amount of charge stored in the electrocatalyst, and not on the applied potential., Author(s): Hong Nhan Nong [sup.1] [sup.2] , Lorenz J. Falling [sup.3] , Arno Bergmann [sup.4] , Malte Klingenhof [sup.1] , Hoang Phi Tran [sup.1] , Camillo Spöri [sup.1] , Rik [...]

Chemical transformations determine the structure of a product, and therefore its properties, which in turn affect complex macroscopic functions such as the metabolic stability of pharmaceuticals or the volatility of perfumes. Therefore, reaction selection can influence the success or failure of a candidate molecule to meet a functional objective. The coupling of an amine with a carboxylic acid to form an amide bond is the most popular chemical reaction used for drug discovery.sup.1. However, there are many other ways to connect these two common functional groups together. Here we show computationally that amines and acids can couple via hundreds of hypothetical yet plausible transformations, and we demonstrate experimentally the application of a dozen such reactions. To investigate the contribution of chemical transformations to properties, we developed a string-based notation and used an enumerative combinatorics approach to produce a map of conceivable amine-acid coupling transformations, which can be charted using chemoinformatic techniques. We find that critical physicochemical parameters of the products, such as partition coefficient and polar surface area, vary considerably depending on the transformation chosen. Data mining the amine-acid coupling system produced here should enable reaction discovery, which we demonstrate by developing an esterification reaction found within the mapped space. Complex molecules with distinct property profiles can also be discovered within the amine-acid coupling system, as we show here via the late-stage diversification of drugs and natural products. All possible chemical transformations between amine and carboxylic acid groups are mapped using an automated string-based combinatorics method, showing that the properties and functions of the products vary considerably over all plausible reactions., Author(s): Babak Mahjour [sup.1] , Yuning Shen [sup.1] , Wenbo Liu [sup.1] , Tim Cernak [sup.1] Author Affiliations: (1) Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann [...]

A simple and efficient approach for the synthesis of N,N'-methylenebisamides through a Selectfluor-mediated oxidative reaction of aromatic amides and N,N-dimethylpropanamide (DMP) is described. Remarkable results clearly reveal that DMP plays a dual role in this reaction, as both a one-carbon source and an environment-friendly solvent. Moreover, the process provides new strategies for the synthesis of bisamides with advantages of operationally simple, insensitive to atmospheric conditions, and good to high yields. Key words: amides, methylenebisamides, Selectfluor, DMP, methylene. Nous derivons une approche simple et efficace pour effectuer la synthese de N,N'-methylenebisamides par une reaction d'oxydation assuree par le Selectfluor entre des amides aromatiques et le N,N-dimethylpropanamide (DMP). Les resultats, remarquables, revelent clairement que le role du DMP est double dans cette reaction, car il agit a la fois comme une source de methylene et comme solvant sans danger pour l'environnement. De plus, cette methode constitue une nouvelle strategie pour effectuer la synthese de bisamides en offrant les avantages d'etre simple sur le plan pratique, d'etre insensible aux conditions atmospheriques et de produire des rendements allant de bons a eleves. [Traduit par la Redaction] Mots-cles : amides, methylenebisamides, Selectfluor, DMP, methylene., Introduction Amides and polyamides, the important biological and medicinal scaffolds, have been widely occurred among numerous biologically active compounds, natural products, (1) pharmaceuticals, polymers, (2) and peptides. (3) In particular, [...]

A kinetic study on nucleophilic substitution reactions of 2,4-dinitrophenyl X-substituted-cinnamates (1a-1f) and Y-substituted-phenyl cinnamates (2a-2g) with a series of alicyclic secondary amines in MeCN at 25.0 [+ or -] 0.1 [degrees]C is reported. The Bronsted-type plots for the reactions of 1a-1f are linear with [[beta].sub.nuc] = 0.47~0.50, indicating that the bond formation between the amine nucleophile and the electrophilic center is advanced slightly in the transition state. The Bronsted-type plot for the reactions of 2a-2g with piperidine is also linear with [[beta].sub.lg] = -0.66, which is a typical [[beta].sub.lg] value for reactions reported previously to proceed through a concerted mechanism. Furthermore, the Hammett plot correlated with [[sigma].sup.-] constants results in much better linearity than that correlated with [[sigma].sup.o] constants, implying that expulsion of the leaving group is advanced in the rate-determining step (RDS). Thus, the reactions are concluded to proceed through a concerted mechanism. The Hammett plots for the reactions of 1a-1f consist of two intersecting straight lines, whereas the corresponding Yukawa-Tsuno plots exhibit excellent linear correlations with [[rho].sub.X] = 0.62~0.71 and r = 0.65~0.68. Apparently, the nonlinear Hammett plots are not due to a change in the reaction mechanism (or the RDS) but are caused by stabilization of the substrate possessing an electron-donating group (EDG) in the cinnamoyl moiety through resonance interactions between the EDG and the C=O bond of the substrate. Medium effects on reactivity and reaction mechanism are also discussed.Key words: aminolysis, Bronsted-type plot, Yukawa-Tsuno plot, concerted mechanism, differential medium effect.Nous presentons une etude cinetique sur des reactions de substitution nucleophile entre des cinnamates 2,4-dinitrophenyliques substitues en position X (1a-1f) ainsi que des cinnamates phenyliques substitues en position Y (2a-2g) et une serie d'amines secondaires alicycliques dans le MeCN a 25,0 [+ or -] 0,1 [degre]C. Les reactions avec les composes 1a-1f presentent des courbes de type Bronsted lineaires avec des valeurs de [[beta].sub.nuc] = 0,47~0,50, ce qui indique que la formation de la liaison entre l'amine nucleophile et le centre electrophile est legerement avancee dans l'etat de transition. Les reactions entre les composes 2a-2g avec la piperidine presentent une courbe de type Bronsted egalement lineaire, avec une constante [[beta].sub.lg] = -0,66, une valeur typique de [[beta].sub.lg] pour les reactions decrites anterieurement comme procedant selon un mecanisme concerte. En outre, la courbe de Hammett mise en correlation avec les constantes [[sigma].sup.-] a presente une bien meilleure linearite qu'avec les constantes [[sigma].sup.o], ce qui implique que l'expulsion du groupe partant est avancee dans l'etape cinetiquement determinante (ECD). Nous avons donc conclu que ces reactions procedaient selon un mecanisme concerte. Les courbes de Hammett des reactions de composes 1a-1f se presentent comme deux lignes droites s'entrecoupant, tandis que les courbes de Yukawa-Tsuno correspondantes montrent d'excellentes correlations lineaires, avec [[rho].sub.X] = 0,62~0,71 et r = 0,65~0,68. En apparence, les courbes de Hammett non lineaires ne sont pas dues a un changement de mecanisme de reaction (ou de l'ECD), mais sont le resultat d'une stabilisation du substrat possedant un groupe electrodonneur (GED) dans de groupement cinnamoyle par des interactions de resonance entre le GED et la liaison C=O du substrat. Les effets du milieu sur la reactivite et le mecanisme de reaction sont egalement abordes. [Traduit par la Redaction]Mots-cles : aminolyse, courbe de type Bronsted, courbe de Yukawa-Tsuno, mecanisme concerte, effet des differents milieux., IntroductionAminolysis of esters has been reported to proceed either through a concerted mechanism or via a stepwise pathway with one or two intermediates (i.e., a zwitterionic tetrahedral intermediate [T.sup.[+ or [...]

A kinetic study is reported for nucleophilic substitution reactions of Y-substituted-phenyl cinnamates (1a-1h) with a series of primary amines including hydrazine in [H.sub.2]O containing 20 mol % DMSO at 25.0 [degrees]C. The Bronsted-type plot for the reaction of 2,4-dinitrophenyl cinnamate (1a) is linear with [[beta].sub.nuc] = 0.57 except hydrazine, which exhibits positive deviation from the linear correlation (i.e., the [alpha]-effect). The Bronsted-type plots for the reactions of 1a-1h with hydrazine and glycylglycine (glygly) are also linear with [[beta].sub.lg] = -0.71 and -0.87, respectively, when 1a is excluded from the linear correlation. Thus, the reactions have been concluded to proceed through a concerted mechanism on the basis of the linear Bronsted-type plots and magnitudes of the [[beta].sub.nuc] and [[beta].sub.lg] values. The [alpha]-effect shown by hydrazine is dependent on electronic nature of the substituent Yin the leaving group, e.g., it increases as the substituent Ybecomes a weaker electron-withdrawing group (or as basicity of the leaving aryloxide increases), indicating that the [alpha]-effect is not due to destabilization of the ground state but mainly due to stabilization of the transition state. A five-membered cyclic TS structure, which could increase nucleofugality of the leaving aryloxide through H-bonding interaction, has been proposed to account for the leaving-group dependent [alpha]-effect found in this study. The theories suggested previously to rationalize the [alpha]-effect found for the related systems are also discussed.Key words: the [alpha]-effect, aryl cinnamates, hydrazine, concerted mechanism, nucleofugality, five-membered cyclic transition state.Nos presentons une etude cinetique portant sur des reactions de substitution nucleophile entre des cinnamates phenyliques substitues en position Y (1a-1h) et une serie d'amines primaires, dont l'hydrazine, dans [H.sub.2]O contenant 20 % mol de DMSO a 25,0 [degre]C. La reaction avec le cinnamate de 2,4-dinitrophenyle (1a) presente une courbe de type Bronsted lineaire avec une valeur de [[beta].sub.nuc] = 0,57, sauf pour l'hydrazine, qui presente une deviation positive par rapport a la correlation lineaire (c.-a-d. l'effet [alpha]). Les courbes de type Bronsted des reactions entre les composes 1a-1h et l'hydrazine ou la glycylglycine (glygly) sont egalement lineaires avec des valeurs de [[beta].sub.lg] = -0,71 et -0,87, respectivement, si l'on exclut le compose 1a de la correlation lineaire. Nous avons donc conclu, d'apres les courbes de type Bronsted et la grandeur des valeurs de [[beta].sub.nuc] et de [[beta].sub.lg], que ces reactions procedaient selon un mecanisme concerte. L'effet [alpha] que presente l'hydrazine est dependant de la nature du substituant Y sur le groupe partant, p. ex., il s'amplifie a mesure que le substituant Y devient un groupe electroattracteur de plus en plus faible (ou que la basicite du groupe partant aryloxyde augmente). Ce comportement indique que l'effet [alpha] n'est pas dû a la destabilisation de l'etat fondamental, mais principalement a la stabilisation de l'etat de transition. Pour expliquer la variation de l'effet [alpha] en fonction de la nature du groupe partant dans cette etude, nous avons propose pour l'etat de transition une structure cyclique a 5 membres, laquelle pourrait, par une liaison hydrogene, accroitre le caractere nucleofuge du groupe partant aryloxyde. D'autres theories proposees anterieurement pour expliquer l'effet [alpha] observe dans des systemes semblables sont egalement abordees. [Traduit par la Redaction]Mots-cles : effet [alpha], cinnamates d'aryles, hydrazine, mecanisme concerte, caractere nucleofuge, etat de transition cyclique a 5 membres., IntroductionOriginally, the term [alpha]-effect was applied to the enhanced nucleophilic reactivity shown by nucleophiles bearing one or more nonbonding electron pairs at the atom [alpha] to the reaction site by [...]

The behaviors of Legendre polynomials representing angular movements are independent of the type of reaction and can be studied in detail paying attention to the changes on effective and centrifugal potentials. For the title reaction, dynamic calculations taking into account the effects of potential energy surfaces have been investigated using the real wave packet method on the most realistic potential energy surface (LZHH) recently obtained. The total electrical dipoles and energies were also calculated in the corresponding quantum states of the molecular system.Key words: angular momentum, Legendre polynomials, centrifugal effect, electrical dipole, potential energy surface.Les polynomes de Legendre qui representent les mouvements angulaires sont independants du type de reaction et peuvent etre etudies en detail en portant attention aux variations des potentiels effectif et centrifuge. Pour la reaction en titre, des calculs dynamiques qui tiennent compte des effets des surfaces d'energie potentielle sont realises ici en utilisant la methode des paquets d'onde reels sur la surface d'energie realiste recemment obtenue (LZHH). Nous calculons aussi les dipoles electriques et les energies des etats quantiques correspondants du systeme moleculaire. [Traduit par la Redaction]Mots-cles: moment angulaire, polynomes de Legendre, effet centrifuge, dipole electrique, surface d'energie potentielle., 1. IntroductionThe atom-diatom ionic reaction Ne + [H.sub.2.sup.+] has been highly interesting in experimental and theoretical studies over the past 30 years because it is a significant reaction in planetary [...]

Polyurethane (PU) is an emerging resin matrix for fiber reinforced polymer (FRP) composites. In the present article, effects of immersion in water or alkaline solution on water uptake and thermomechanical properties of a PU were investigated. A traditional epoxy resin matrix was investigated for comparison. As found, unlike the epoxy (hydrolysis occurred in case of alkaline solution), water and alkaline solution immersion showed a similar effect for the PU resin. For both immersion, the water uptake of the PU system reached the equilibrium content of 2.5%-2.7%, in accordance with the Fick's law. Glass transition temperature ([T.sub.g]) of the PU decreased rapidly after the first month of immersion and then leveled off. Both immersion for a short term (e.g., 1 month of immersion) led to an obvious decrease in the tensile strength, while long-term immersion brought in obvious recovery. Remarkable increase in the elongation at break (up to 16.6%) due to immersion was found. The higher the immersion temperatures, the less the degradation of the tensile strength. The variations of the thermalmechanical properties were attributed to the waterinduced plasticization and the postcuring-induced increase of the crosslinkage. Compared with the common epoxy system, the PU system showed better resistance to the immersion. POLYM. ENG. SCI., 58:2276-2287, 2018., INTRODUCTIONSince the 1930s, polyurethane (PU) resins (PUs) with a particular function group, -NHCOO-, have been widely used as coatings [1], foams [2], rubbers [3], shape-memory polymers [4], insulation materials [5], [...]

This work describes the development of an optimized spin dope for the production of open-porous, mechanically stable fiber sorbents. The fiber sorbents in this work consist of Torlon[R] polymer matrix with dispersed zeolite particles to act as the sorbent sites. Initial spinning attempts with dopes consisting of Torlon[R], 13X, n-methylpyrrolidone (NMP) and water yielded fibers that were prone to breaks during production and had a large number of macrovoids. To remedy this, polyvinylpyrrolidone (PVP) was introduced in the dope as a pore former and macrovoid suppressant. A separate phase diagram was developed to accommodate PVP and a new preferred spin dope composition was identified. Fibers were spun based on this concentration with adequate spinning behavior. Microscopy analysis showed that PVP was successful in reducing the prevalence of macrovoids in the fiber cross section. High sorbent wall permeance was also retained with the PVP. Further analysis of permeance measurements revealed that Knudsen flow was dominant over Poiseuille flow. The estimated pore sizes implying that the transport process lies in the transition region between molecular and Knudsen diffusion. 2018., INTRODUCTIONCoal-fired power plants remain the largest source of C[O.sub.2] emissions in many countries [1, 2], and are likely to remain so in the foreseeable future [3]. Carbon capture from power [...]

The addition of 4-ethyl-3-thiosemicarbazide to benzaldehyde and boronic acid containing derivatives afforded the corresponding thiosemicarbazones (1-3) or benzodiazaborines (4-6) depending on the position of the boronic acid within the ring. All compounds have been characterized fully including an X-ray diffraction study of the methoxy-containing benzodiazaborine 6. Attempts to coordinate thiosemicarbazones 2 and 3 to palladium(II) acetate were unsuccessful; however, addition of the non-boron-containing derivative 1 to palladium afforded complex 7 whose molecular structure was determined by an X-ray diffraction study. The initial bioactivities of compounds 1-7 were examined against two fungi, Aspergillus niger and Saccharomyces cerevisiae, and two bacteria, Bacillus cereus and Pseudomonas aeruginosa. Key words: antimicrobial, benzodiazaborines, boron, palladium, thiosemicarbazones. L'addition du 4-éthyl-3-thiosemicarbazide au benzaldéhyde et à des dérivés contenant un acide boronique a produit les thiosemicarbazones (1-3) ou les benzodiazaborines (4-6) correspondantes selon la position de l'acide boronique sur le noyau aromatique. Nous avons effectué la caractérisation complète de tous les composés, y compris par une étude de diffraction des rayons X à laquelle nous avons soumis la benzodiazaborine méthoxylée 6. Nous avons tenté sans succès d'effectuer la coordination des thiosemicarbazones 2 et 3 à l'acétate de palladium(II). Toutefois, l'addition du dérivé 1, exempt de bore, au palladium a produit le complexe 7 dont nous avons déterminé la structure moléculaire par diffraction des rayons X. Nous avons examiné pour commencer la bioactivité des composés 1-7 contre deux champignons, Aspergillus niger et Saccharomyces cerevisiae, et deux bactéries, Bacillus cereus et Pseudomonas aeruginosa. [Traduit par la Rédaction] Mots-clés : antimicrobien, benzodiazaborines, bore, palladium, thiosemicarbazones., Introduction There has been recent considerable interest in boron-containing molecules for their use in pharmaceutical chemistry. (1) Among the many types of boron compounds being investigated for their therapeutic potential, [...]

The development of new methods for the control of preparations widely used in cosmetics and medicine is a task of high current importance. Hyaluronic acid is one of the most often used components of anti-age cosmetics; its action and impact on the human skin depends on the concentration in the solution. The known methods of the determination of the concentration of hyaluronic acid are expensive, require complex sample preparation, and cannot be used in routine analyses. In this work, for the rapid determination of the concentration of hyaluronic acid in solutions used in the production of skin cosmetics, we propose the method of oxythermography, which does not require chemical reagents. The oxidant is air oxygen. The absolute limit of detection for hyaluronic acid is about 4 [micro]g for a sample volume of 5 [micro]L., Author(s): B. K. Zuev [sup.1] , V. G. Filonenko [sup.1] , D. S. Nesterovich [sup.2] , P. D. Polikarpova [sup.2] Author Affiliations: (Aff1) 0000 0004 0380 8849, grid.439081.7, Vernadsky Institute [...]

Two novel p-functionalized push-pull zinc porphyrins with amine or phenyl push-groups and cyclic imide or carboxylic esters pull-groups have been newly synthesized for light energy harvesting applications. The ethynylphenyl spacers extended the conjugation of the porphyrin [pi]-systems, as reflected by their red-shifted absorbance and fluorescence spectra. Computational studies performed at the B3LYP/6-31G* level indicated no steric hindrance between the porphyrin w-system and the substituents. The calculated HOMO and LUMO orbitals displayed significant delocalization in 1, where the electron density in the HOMO was localized over the push groups, whereas the LUMO was extended over the porphyrin [pi]- and pull-groups. On the other hand, 2 did not display significant orbital segregation, which is attributed to its weaker push-pull character. Electrochemical studies revealed smaller HOMO-LUMO gaps for the push-pull zinc porphyrins. As a consequence of the push-pull effects, reduction in fluorescence intensity and lifetime was observed. Femtosecond transient absorption spectral studies revealed successful formation of singlet excited state in both of the push-pull porphyrins. Donor-acceptor conjugates were subsequently built and characterized by coordinating an electron acceptor, [C.sub.60]Im, via metal-ligand axial coordination. Efficient photo-induced charge separation in both donor-acceptor conjugates was witnessed wherein the charge-separated states persisted tens of nanoseconds prior returning to the ground state. Key words: push-pull zinc porphyrin, fullerene, metal-ligand axial coordination, photoinduced electron transfer. Nous avons realise la premiere synthese de deux nouvelles porphyrines-zinc de type<< push-pull>>fonctionnalisees en positions p, dans lesquelles les groupes electrodonneurs sont des amines ou des groupes phenyl et les groupes electroattracteurs, un imide cyclique ou des esters carboxyliques, en vue d'applications de recuperation d'energie lumineuse. Les groupes ethynylphenyl tenaient lieu d'espaceurs servant a etendre les systemes de conjugaison [pi]des porphyrines, comme en temoigne le deplacement vers le rouge des spectres d'absorbance et de fluorescence de ces composes. Des etudes de modelisation realisees au niveau B3LYP/6-31G (*) n'ont pas revele d'encombrement sterique entre le systeme w des porphyrines et leur substituants. La modelisation des orbitales HOMO et LUMO du compose 1 a revele une delocalisation importante, la densite electronique de la HOMO etant localisee sur les groupes electrodonneurs, tandis que la LUMO s'etendait sur le systeme w de la porphyrine et les groupes electroattracteurs. Par contre, le compose 2 n'a pas presente de segregation orbitalaire marquee, ce qui s'explique par son caractere << push-pull >> plus faible. Des etudes electrochimiques menees sur les porphyrines-zinc de type << push-pull >> ont revele que leurs bandes interdites HOMO-LUMO etaient plus etroites. Les effets de type << push-pull >> se sont traduits par une reduction de l'intensite et de la duree de vie de la fluorescence. L'analyse des spectres d'absorption des especes transitoires a l'echelle de la femtoseconde a revele que les deux porphyrines de type<>donnaient lieu a la formation d'un etat excite singulet. Nous avons par la suite forme les conjugues donneur-accepteur par coordination axiale metal-ligand d'un accepteur d'electron, le [C.sub.60]Im, et nous les avons caracterises. Nous avons observe qu'une separation de charge photo-induite se produisait efficacement dans les deux conjugues donneur-accepteur, et que ces etats de separation de charge ont persiste des dizaines de nanosecondes avant de revenir a l'etat fondamental. [Traduit par la Redaction] Mots-cles: porphyrine zinc de type <>, fullerene, coordination axiale metal-ligand, transfert electronique photo-induit., Introduction Push-pull porphyrins have been of intense research interest in recent years owning to their exceptional performance in dyesensitized solar cells. (1-5) The important roles of the push (electrondonating) and [...]

Various reaction mechanisms such as cyclization, oxidation, dehydrogenation, and crosslinking are studied during stabilization of electrospun polyacrylonitrile nanofibers using different in situ techniques such as differential scanning calorimetry (DSC), shrinkage measurement, and dynamic mechanical analysis (DMA). DSC results show that oxidation preferentially occurs in cyclized structure. It is also found that the cyclization reaction has the highest activation energy followed by oxidation/dehydrogenation and crosslinking reactions. In situ shrinkage measurement and DMA data are used to study the extent of cyclization and cross-linking reactions, respectively, in air. Comparing the in situ shrinkage measurement with DSC data, it is found that cyclization reaction in air progresses in two different mechanisms such as radical cyclization, which depends only on the temperature and ionic cyclization, which is limited by the rate of oxygen diffusion. It is found that complete cyclization time occurs at about 189 min for isothermal heat treatment at 260[degrees]C with 5[degrees]C/min ramp, while cross-linking reaction becomes dominant at 132 min. POLYM. ENG. SCI., 58:1315-1321, 2018., INTRODUCTION Electrospun carbon nanofibers (eCNFs) are gaining huge interest as composite reinforcements, conductive fillers, cathodes in rechargeable batteries, supercapacitors, filters, sensors, and heat management materials due to continuous fibrous structure, [...]

Polylactide (PLA) is a eco-friendly and biodegradable material that can be synthesized from renewable resources. PLA features poly(D-lactic acid) (PDLA) and poly(L-lactic acid) (PLLA) enantiomers. Supercritical fluid (SCF) technology is a very promising method for the stereocomplexation between PDLA and PLLA enantiomers. This study acquires stereocomplex (sc-)PLA particles with diverse sizes and behaviors by controlling the experimental conditions. Various parameters including polymer concentration, reaction temperature, stirring speed, pressure reducing speed, and final temperature were controlled to adjust size and behavior of sc-PLA particles. Additionally, we analyzed the effect of subsequent processing following SCF (such as homogenization, mechanical stirring, and sonication) on the size and morphological behavior of sc-PLA particles. Finally, the mechanical strengths of different PLA composites featuring different sc-PLA filler sizes were determined. The mechanical strength of PLA composites was significantly improved when using smaller filler sizes., INTRODUCTION Polylactide (PLA), which includes poly(D-lactic acid) (PDLA) and poly(L-lactic acid) (PLLA), has good biological safety and physical properties for use in various industries [1-5]. PLA has emerged as a [...]

Poly(ethylene oxide) (PEO) based polyurethaneurea-silica nanocomposites were prepared by solution blending and characterized by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Differential Scanning Calorimetry and tensile testing. The colloidal silica nanoparticles with an average size of 50 nm were synthesized by modified Stober method in isopropanol. Silica particles were incorporated into three cycloaliphatic polyurethaneurea (PUs) copolymers based on PEO oligomers with molecular weights of 2,000, 4,600, and 8,000 g/mol. Hard segment content of PUs was constant at 30% by weight. Silica content of the PU nanocomposites varied between 1 and 20% by weight. Soft segment (SS) glass transition and melting temperatures slightly increased with increasing filler content for all the copolymers. Degree of SS crystallinity first increased with 1% silica incorporation and subsequently decreased by further silica addition. Elastic modulus and tensile strengths of PU copolymers gradually increased with increasing amount of the silica filler. Elongation at break values gradually decreased in PEO-2000 based PU copolymer with increasing silica content, whereas no significant change was observed in PUs based on PEO-4600 and PEO-8000. Enhancement in tensile properties of the materials was mainly attributed to the homogeneous distribution of silica filler in polymer matrices and strong polymer-filler interactions., INTRODUCTION Polymeric nanocomposites have been a focus of attention particularly because of their enhanced physicochemical, thermal, mechanical, and other engineering properties, enabling their use in a wide range of applications, [...]

The present contribution describes the systematic structural diversification of the [[KAPPA].sup.2]-P,N DalPhos ligand family in an effort to improve catalytic efficiency in the monoarylation of ammonia and acetone. The study is focused primarily on modifying the backbone phenylene linker, while retaining the same bite angle and steric bulk as the Mor-DalPhos ligand through the use of P[(1-Ad).sub.2] and morpholine donors. Eight new variants of Mor-DalPhos were prepared; two of these feature a pyridine linker (L1, L2), and five others feature either electron-donating (L3, L4) or electron-withdrawing (L5-L7) substituents on the phenylene linker. Additionally, thiomorpholino substitution (L8) was performed to investigate the effects of a possible tridentate coordination mode. Precatalyst complexes of the general formula LPd(cinnamyl)Cl were prepared and characterized in both solution and solid state. Solution studies demonstrated a significant degree of lability in the Pd-N bond, whereby dynamic behavior is seen to be dependent on the nature of the ligand backbone. The utility of these new ligands in the palladium-catalyzed monoarylation of ammonia or acetone was then surveyed. Notably, pyridine-derived ligand variants (L1, L2) were observed to out-perform parent Mor-DalPhos in the latter transformations. Key words: amination, catalysis, cross-coupling, ligand design, palladium. Dans la presente contribution, nous decrivons la diversification structurale systematique de la famille de ligands [[kappa].sup.2]-P,N-DalPhos en vue d'ameliorer l'efficacite catalytique de la monoarylation de l'ammoniaque et de l'acetone. Dans cette etude, nous nous sommes principalement interesses a modifier l'espaceur phenylene du squelette du ligand Mor-DalPhos, tout en conservant le meme angle de chelation et le meme encombrement sterique, en utilisant des phosphines de structure P[(1-Ad).sub.2] portant un donneur de type morpholine. Nous avons prepare huit nouvelles variantes du ligand Mor-DalPhos; dont deux presentent un espaceur de type pyridine (L1, L2) et les cinq autres, des substituants soit electrodonneurs (L3, L4) ou electroattracteurs (L5-L7) disposes sur l'espaceur phenylene. De plus, nous avons realise une substitution par le groupe thiomorpholine (L8) pour examiner les effets d'un possible mode de coordination tridentate. Nous avons prepare les complexes precatalytiques de formule generale LPd(cinnamyl)Cl et les avons caracterises en solution comme a l'etat solide. Selon les resultats des experiences en solution, la liaison Pd-N a revele un degre de labilite important, lequel est determine par la nature du squelette du ligand dont semble dependre le comportement dynamique. Nous avons explore l'utilite de ces nouveaux ligands dans les monoarylations de l'ammoniaque et de l'acetone catalysees par le palladium, dans lesquelles nous avons notamment observe que les analogues du ligand derives de la pyridine (L1, L2) presentaient un meilleur rendement qu'avec le ligand Mor-DalPhos d'origine. [Traduit par la Redaction] Mots-cles : amination, catalyse, couplage croise, conception de ligand, palladium., Introduction The development of new classes of ancillary ligands, such as tertiary monodentate/bidentate (bis)phosphines (1-4) and N-heterocyclic carbenes (NHCs), (5-8) has permitted great advancements in the scope and efficiency of [...]

We have synthesized bismuth complexes incorporating polydentate mono- and di-thiolate ligands and examined their utility as water-tolerant Lewis acid catalysts. The reaction of Bi[(OAc).sub.3] or Bi[(N[O.sub.3]).sub.3]-5[H.sub.2]O and the corresponding mono- or di-thiol(ate) yielded the compounds [(SNNS)Bi(OAc)] (4), [(SNNSPr)Bi(OAc)] (5), [(NN[S.sub.2])Bi(OAc)] (6), [(ON[S.sub.2])Bi(OAc)] (7), [(ON[S.sub.2])Bi(N[O.sub.3])] (8), and [[(NNS).sub.2]Bi][N[O.sub.3]] (9) [[H.sub.2](SNNS) = N,N'-dimethyl-N,N'-bis(2-mercaptoethyl)ethylenediamine; [H.sub.2](SNNSPr) = N,N'-diethyl-N,N'-bis(2-mercaptoethyl)propanediamine; [H.sub.2](NN[S.sub.2]) = N,N-diethyl-N',N'-bis(2-mercaptoethyl)ethanediamine; [H.sub.2](ON[S.sub.2]) = 2-methoxyethyl-bis(2-mercaptoethyl)amine; H(NNS) = N,N-diethyl-N'-(2-mercaptoethyl)ethanediamine]. The solid-state structures of 4-8 show similar distorted pentagonal pyramidal geometries at the bismuth centre with a thiolate sulfur atom in the axial site, whereas 8 shows second structural arrangement with a distorted trigonal bipyramidal geometry at bismuth. The cation of 9 shows two NNS-bonded ligands and a distorted octahedral geometry at bismuth. Two-dimensional NMR studies of 4-8 show geminal [sup.1]H coupling in -SC[H.sub.2]C[H.sub.2]N- groups and suggests strong dative Bi-N intramolecular interactions. Bi[(N[O.sub.3]).sub.3]-5[H.sub.2]O and Bi[Cl.sub.3] show high activity toward the esterification of stearic acid, Bi[(N[O.sub.3]).sub.3]-5[H.sub.2]O, and 4-7 and 9 show high activity toward the transesterification of methyl stearate in butanol, and 7 shows moderate activity as a catalyst for the transesterification of glyceryl trioctanoate in methanol. Key words: bismuth, thiolates, Lewis acid catalysts, transesterification, biofuels. Nous avons synthétisé des complexes de bismuth comportant des ligands polydentates à base de monothiolates et de dithiolates et avons étudié leur utilité comme acides de Lewis pour servir de catalyseurs résistants à l'eau. La réaction entre le Bi[(OAc).sub.3] ou le Bi[(N[O.sub.3]).sub.3]*5[H.sub.2]O et les monothiol(ate)s ou dithiol(ate)s correspondants a produit les composés [(SNNS)Bi(OAc)] (4), [(SNNSPr)Bi(OAc)] (5), [(NN[S.sub.2])Bi(OAc)] (6), [(ON[S.sub.2])Bi(OAc)] (7), [(ON[S.sub.2])Bi(N[O.sub.3])] (8) et [[(NNS).sub.2]Bi][N[O.sub.3]] (9) [[H.sub.2](SNNS) = N,N'-diméthyl-N,N'-bis(2-mercaptoéthyl)éthylènediamine; [H.sub.2](SNNSPr) = N,N'-diéthyl-N,N'-bis(2-mercaptoéthyl)propanediamine; [H.sub.2](NN[S.sub.2]) = N,N-diéthyl-N',N'-bis(2-mercaptoéthyl)éthanediamine; [H.sub.2](ON[S.sub.2]) = 2-méthoxyéthyl-bis(2-mercaptoéthyl)amine; H(NNS) = N,N-diéthyl-N'-(2-mercaptoéthyl)éthanediamine]. Les structures à l'état solide des composés 4-8 présentent à l'atome central de bismuth des géométries pentagonales déformées similaires avec un atome de soufre du thiolate en position axiale, tandis que le composé 8 présente un deuxième arrangement structural dont la géométrie à l'atome de bismuth est bipyamidale trigonale déformée. Le cation du composé 9 présente deux ligands NNS liés et une géométrie octaédrique déformée à l'atome de bismuth. Les études en RMN à deux dimensions portant sur les composés 4-8 montrent un couplage des [sup.1]H géminaux dans les groupes -SC[H.sub.2]C[H.sub.2]N- et laisse supposer que les interactions Bi-N intramoléculaires sont fortement bipolaires. Le Bi[(N[O.sub.3]).sub.3]*5[H.sub.2]O et le Bi[Cl.sub.3] montrent une forte activité pour catalyser l'estérification de l'acide stéarique. Par ailleurs, le Bi[(N[O.sub.3]).sub.3]*5[H.sub.2]O montre aussi, ainsi que les composés 4-7 et le composé 9, une forte activité pour catalyser la transestérification du stéarate de méthyle dans le butanol. Le composé 7 présente en outre une activité modérée pour catalyser la transestérification du trioctanoate de glycéryle dans le méthanol. [Traduit par la Rédaction] Mots-clés: bismuth, thiolates, catalyseurs à base d'acides de Lewis, transestérification, biocarburants., Introduction A major focus in green chemistry over the past two decades has been the development of synthetic methods that involve ambient atmosphere conditions and environmentally benign solvents such as [...]

The P-functionalization of dithieno [3,2-b:2',3'-d]phosphole oxides via reaction of a P-chloro derivative with aromatic amines and alcohols is reported. The reactions proceed rapidly and provide the products in good yields, highlighting the synthetic versatility of the P-chloro dithienophosphole oxide toward effectively modifying the molecular scaffold without the need for elaborate phosphorus precursor syntheses. The resulting phosphinic amide and ester products show interesting photophysics that strongly depend on the nature of the P-substituent such as high luminescence quantum yields for the ester derivatives, as well as aggregation-induced enhanced emission for the amide derivative. The phosphinic amide species also shows intriguing self-assembly in the solid state via hydrogen bonding. Key words: phosphorus heterocycles, conjugated materials, self-assembly, luminescence, DFT calculations. Nous présentons la fonctionnalisation de l'atome de phosphore dans des oxydes de dithiéno[3,2-b:2',3'-d]phosphole par réaction d'un dérivé P-chloré avec des amines et des alcools aromatiques. Les réactions s'effectuent rapidement et les produits sont formés en bons rendements, ce qui met en évidence la polyvalence de l'oxyde de dithiénophosphole P-chloré en synthèse et permet de modifier efficacement la structure moléculaire de base sans avoir recours à des synthèses élaborées pour la préparation d'un précurseur phosphoré. Les amides et esters phosphiniques que nous avons obtenus présentent des propriétés photophysiques intéressantes qui dépendent fortement de la nature du substituant sur l'atome de phosphore. Entre autres, les dérivés ester présentent des rendements quantiques de luminescence élevés et les dérivés amide, une amplification d'émission induite par agrégation. Le composé d'amide phosphinique a également présenté des propriétés intrigantes d'autoassemblage à l'état solide assuré par des liaisons hydrogène. [Traduit par la Rédaction] Mots-clés: hétérocycles phosphorés, composés conjugués, autoassemblage, luminescence, calculs DFT., Introduction Over the past decade, dithieno[3,2-b:2',3'-d]phospholes have been developed into versatile building blocks for organoelectronic materials. (1) One of the advantages of phospholes is the structure diversity afforded by the [...]

Two N-heterocyclic phosphines with exocyclic SCN substituents were synthesised via metathesis of chlorophosphine precursors with KSCN and fully characterised. The crystallographic studies reveal that the products exhibit pronounced structural differences. The thiocyanato unit binds in one case via the nitrogen atom to yield a molecular structure with a slightly elongated P-N single bond and, in the other case, via the sulfur atom to form a structure that is best described as an ion pair and forms a one-dimensional coordination polymer in the crystal. DFT calculations suggest that the P-N and P-S interactions can be described as covalent and dative bonds, respectively, and that the structural differences correlate with the different cation stabilities of the individual phosphenium cation fragments. Key words: N-heterocyclic phosphines, ambident Lewis bases, dative bonds, coordination isomerism. Nous avons synthétisé deux phosphines N-hétérocycliques portant des substituants SCN exocycliques par voie de métathèse de précurseurs chlorophosphine avec le KSCN, et nous les avons soumis à une caractérisation complète. Les analyses cristallographiques révèlent que les produits présentent des différences structurales importantes. L'unité thiocyanate se lie dans un cas par l'atome d'azote pour produire une structure moléculaire caractérisée par une liaison simple P-N légèrement allongée, et dans l'autre cas, par l'atome de soufre pour former une structure qui s'apparente davantage à une paire d'ions créant un polymère de coordination unidimensionnel dans le cristal. Les calculs DFT indiquent que les interactions P-N et P***S pourraient être décrites comme des liaisons covalentes et bipolaires, respectivement, et que les différences structurales sont corrélées avec la stabilité des différents fragments cationiques de phosphénium. [Traduit par la Rédaction] Mots-clés: phosphines N-hétérocycliques, bases de Lewis ambidentates, liaisons bipolaires, isomérisme de coordination., Introduction The reaction between a Lewis acid (electron pair acceptor) and a Lewis base (electron pair donor) to form a complex (or Lewis pair) is one of the most fundamental [...]

The previously unreported carbene-phosphine adduct (IPr)P[Cl.sub.2][N.sub.3] [IPr = [(HCNDipp).sub.2]C:; Dipp = 2,6-[sup.i][Pr.sub.2][C.sub.6][H.sub.3]] was synthesized and used as a synthon toward the elusive dichlorophosphazene monomer unit, [[Cl.sub.2]P=N]. (IPr)P[Cl.sub.2][N.sub.3] was found to undergo halide and azide abstraction when combined with various electrophiles and its thermolysis yielded the unexpected Staudinger reaction product (IPr=N)P[Cl.sub.2]. Key words: Staudinger reaction, phosphazenes, carbene, phosphine. Nous avons réalisé la première synthèse de l'adduit carbène-phosphine (IPr)P[Cl.sub.2][N.sub.3], [IPr = [(HCNDipp).sub.2]C:; Dipp = 2,6-[sup.i][Pr.sub.2][C.sub.6][H.sub.3]] et l'avons employé comme synthon en vue de préparer l'unité monomérique dichlorophosphazène hypothétique [[Cl.sub.2]P=N]. Nous avons observé qu'en présence de divers électrophiles, l'adduit (IPr)P[Cl.sub.2][N.sub.3] subissait une abstraction des atomes d'halogène et de l'azoture, et que sa thermolyse donnait lieu à un produit inattendu, le (IPr=N)P[Cl.sub.2], issu de la réaction de Staudinger. [Traduit par la Rédaction] Mots-clés: réaction de Staudinger, phosphazènes, carbène, phosphine., Introduction Originally referred to as 'inorganic rubber', poly(dichlorophosphazene) [[[Cl.sub.2]P=N].sub.n] was first reported by Stokes in 1895. (1) This important parent polymer is typically synthesized by the ring-opening polymerization (ROP) of [...]

Palladium-catalyzed decarboxylative arylation is reported using pyrroles N-protected with the 2-(trimethylsilyl) ethoxymethyl (SEM) group and featuring 2-, 3-, and 4-substituents about the pyrrolic framework. In contrast to N-protected pyrroles previously used in decarboxylative arylation, the use of SEM allows deprotection under mild conditions. Key words: pyrroles, decarboxylative arylation, pyrrole N-protection, SEM, substituted pyrrolic core. Nous faisons état d'une arylation décarboxylante catalysée par le palladium, réalisée avec des pyrroles aminoprotégés par le groupe 2-(triméthylsilyl)éthoxyméthyl (SEM) qui portent autour du noyau pyrrolique des substituants aux positions 2, 3 et 4. Contrairement aux groupes aminoprotecteurs employés avec les pyrroles soumis précédemment à l'arylation décarboxylante, l'emploi du groupe SEM permet une déprotection en conditions douces. [Traduit par la Rédaction] Mots-clés: pyrroles, arylation décarboxylante, aminoprotection de pyrrole, SEM, noyau pyrrolique substitué., Introduction Considerable effort has been made to address the development of efficient synthetic strategies to form (hetero)aryl-(hetero)aryl (1-3) C-C bonds that proceed under mild reaction conditions and with high selectivity [...]

The reactivity of aluminium compounds is dominated by their electron deficiency and consequent electrophilicity; these compounds are archetypal Lewis acids (electron-pair acceptors). The main industrial roles of aluminium, and classical methods of synthesizing aluminium-element bonds (for example, hydroalumination and metathesis), draw on the electron deficiency of species of the type AlR.sub.3 and AlCl.sub.3.sup.1,2. Whereas aluminates, [AlR.sub.4].sup.-, are well known, the idea of reversing polarity and using an aluminium reagent as the nucleophilic partner in bond-forming substitution reactions is unprecedented, owing to the fact that low-valent aluminium anions analogous to nitrogen-, carbon- and boron-centred reagents of the types [NX.sub.2].sup.-, [CX.sub.3].sup.- and [BX.sub.2].sup.- are unknown.sup.3-5. Aluminium compounds in the +1 oxidation state are known, but are thermodynamically unstable with respect to disproportionation. Compounds of this type are typically oligomeric.sup.6-8, although monomeric systems that possess a metal-centred lone pair, such as Al(Nacnac).sup.Dipp (where (Nacnac).sup.Dipp = (NDippCR).sub.2CH and R = .sup.tBu, Me; Dipp = 2,6-.sup.iPr.sub.2C.sub.6H.sub.3), have also been reported.sup.9,10. Coordination of these species, and also of ([eta].sup.5-C.sub.5Me.sub.5)Al, to a range of Lewis acids has been observed.sup.11-13, but their primary mode of reactivity involves facile oxidative addition to generate Al(iii) species.sup.6-8,14-16. Here we report the synthesis, structure and reaction chemistry of an anionic aluminium(i) nucleophile, the dimethylxanthene-stabilized potassium aluminyl [K{Al(NON)}].sub.2 (NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethylxanthene). This species displays unprecedented reactivity in the formation of aluminium-element covalent bonds and in the C-H oxidative addition of benzene, suggesting that it could find further use in both metal-carbon and metal-metal bond-forming reactions.An aluminium compound is synthesized in which the aluminium is formally anionic; reactions with various substrates suggest that this compound acts as the nucleophilic partner in both metal-carbon and metal-metal bond-forming reactions., Author(s): Jamie Hicks [sup.1] , Petra Vasko [sup.1] [sup.2] , Jose M. Goicoechea [sup.1] , Simon Aldridge [sup.1] Author Affiliations:(1) Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, [...]

Residence time distribution (RTD) is an important factor in melt extrusion as it strongly influences the product quality. It can cause degradation of the active pharmaceutical ingredient (API), which can be reduced by shorter mean residence times, and the content uniformity, which can be improved by broadening the RTD caused by axial mixing. In our study, we developed an inline video analysis that to date has mainly been applied offline. For extrusion, hydrophilic polymer and a surfactant were used as a molten matrix, in which an API was embedded. The video analysis consisted of four steps: (1) segmentation of the image to mask the strands, (2) calculation of average color values for the segmented pixels of each frame, (3) fitting of the obtained color curve with an analytical solution, and (4) calculating several RTD measures (e.g., the minimal and mean RT) for better comparison of the results. The RTD measures were responses in the design of experiments (DoE), which included the process parameters screw design, screw speed, and throughput. This analysis clearly showed that screw design had the strongest effect on the RTD measures. The results suggest that video analysis is a suitable tool for inline RTD measurements., INTRODUCTION Melt extrusion combined with spheronization is a well-known pharmaceutical process for producing nearly spherical pellets [1], which can be filled into capsules. An alternative process for producing pellets is [...]

The rate constants for reactions involved in the radiolysis of water under relevant thermodynamic conditions in supercritical water-cooled reactors are estimated for inputs in simulations of the radiation chemistry in Generation IV nuclear reactors. We have discussed the mechanism of each chemical reaction with a focus on non-equilibrium reactions. We found most of the reactions are activation controlled above the critical point and that the rate constants are not significantly pressure dependent below 300 [degrees]C. This work will aid industry with developing chemical control strategies to suppress the concentration of eroding species. Key words: Generation IV reactors, supercritical water, kinetics, radiation chemistry. Nous avons estime les constantes de vitesse des reactions intervenant dans la radiolyse de l'eau dans les conditions thermodynamiques des reacteurs refroidis a l'eau supercritique et nous les avons integrees a des calculs de simulation de la radiochimie dans les reacteurs nucleaires de quatrieme generation. Nous nous sommes interesses au mecanisme de chaque reaction chimique, en particulier les reactions hors equilibre. Nous avons decouvert que l'activation de la plupart des reactions se produit au-dessus du point critique et que, sous les 300 [degrees]C, la pression n'a pas d'influence significative sur les constantes de vitesse. Ces travaux pourront aider l'industrie a mettre au point des strategies de protection chimique en vue prevenir la concentration d'especes corrosives. [Traduit par la Redaction] Mots-cles: reacteurs de 4e generation, eau supercritique, cinetique, radiochimie., Introduction A supercritical water cooled reactor (SCWR) uses supercritical water (SCW) (water above its critical point of 374 [degrees]C, 221 bar) as its coolant. (1) SCWR is one of the [...]

A short enantioselective total synthesis of 1-deoxygalactonojirimycin (migalastat) has been achieved that does not rely on chiral pool starting materials or biocatalysis. Instead, this synthesis exploits a one-pot proline-catalyzed [alpha]-chlorination and aldol reaction of a commercially available aldehyde to assemble the entire carbon skeleton in a single step. The key role played by a nitrogen protecting group in the final epoxide opening reaction is highlighted as is the amenability to access structural analogues using this route. Key words: 1-deoxygalactonojirimycin, iminosugar, organocatalysis, chlorohydrin, total synthesis, natural product. Nous avons realise une courte synthese totale enantioselective de la 1 desoxygalactonojirimycine (migalastat) sans faire appel a des produits de depart issus du bassin chiral ou a la biocatalyse. Cette synthese, realisee en recipient unique, exploite plutot une [alpha]-chloration catalysee par la proline et une aldolisation a partir d'un aldehyde commercial, et permet d'assembler tout le squelette carbone en une seule etape. Nous soulignons le role cle que joue le groupe protecteur de l'azote dans la reaction finale d'ouverture d'epoxyde ainsi que la possibilite d'acceder a des analogues structuraux par cette voie. [Traduit par la Redaction] Mots-cles : 1-desoxygalactonojirimycine, iminosucre, organocatalyse, chlorhydrine, synthese totale, produit naturel., Polyhydroxylated piperidines, or iminosugars, have received much attention as biological tools and drug leads with potential applications in the treatment of cancer, viral infections, diabetes, and lysosomal storage disorders. (1-3) [...]

UiO-66 and a muconic acid functionalized derivative of UiO-66 (UiO-66-MA) were synthesized via the solvothermal method to determine if the muconic acid could undergo a cheletropic reaction in the presence of sulfur dioxide inside the metal-organic framework (MOF). Both MOFs were exposed to a constant flow of sulfur dioxide, and UiO-66-MA was observed to take up three times more sulfur dioxide than unfunctionalized UiO-66. Despite the improved uptake of sulfur dioxide in UiO-66-MA, NMR and IR data indicate that no chemical change occurred to the muconic acid indicating that a cheletropic reaction did not occur. We thus propose that the increased adsorption is due to either an interaction between the sulfur dioxide and unbound carboxylic acid from the muconic acid or a favourable interaction between the butadiene of muconic acid and sulfur dioxide. Key words: sulfur dioxide, adsorption, UiO-66, breakthrough, metal-organic frameworks. Nous avons synthetise le compose UiO-66 et un derive fonctionnalise par l'acide muconique (UiO-66-MA) en utilisant une methode solvothermale afin de determiner si l'acide muconique pouvait subir une reaction chelotropique en presence de dioxyde de soufre a l'interieur du reseau metallo-organique (MOF, acronyme anglais pour metal-organic framework). Ces deux MOF ont ete exposes a un debit constant de dioxyde de soufre. Nous avons alors observe que le compose UiO-66-MA captait trois fois plus de dioxyde de soufre que le compose non fonctionnalise UiO-66. Bien que le compose UiO-66-MA capte plus de dioxyde de soufre, les donnees RMN et IR indiquent que la fonction acide muconique est demeuree intacte sur le plan chimique, ce qui exclut la possibilite qu'une reaction chelotropique ait eu lieu. Nous avancons donc l'hypothese que cette adsorption accrue soit attribuable a une interaction entre le dioxyde de soufre et un acide carboxylique non lie de l'acide muconique ou a une interaction favorable entre le butadiene de l'acide muconique et le dioxyde de soufre. [Traduit par la Redaction] Mots-cles : dioxyde de soufre, adsorption, UiO-66, percee, reseaux metallo-organiques., Introduction Sulfur dioxide is a by-product of fossil fuel burning. Under humid environments, sulfur dioxide rapidly reacts with water (e.g., in the atmosphere or lungs) to form sulfuric acid. As [...]

Predicting the three-dimensional structure of a protein from its amino acid sequence requires a complete understanding of the molecular forces that influences the protein folding process. Each possible conformation has its corresponding potential energy, which characterizes its thermodynamic stability. This is needed to identify the primary intra- and intermolecular interactions, so that we can reduce the dimensionality of the problem, and create a relatively simple representation of the system. Investigating this problem using quantum chemical methods produces accurate results; however, this also entails large computational resources. In this study, an improved two-rotor potential energy function is proposed to represent the backbone interactions in amino acids through a linear combination of a Fourier series and a mixture of Gaussian functions. This function is applied to approximate the 20 amino acid diamide Ramachandran-type PESs, and results yielded an average RMSE of 2.36 kJ [mol.sup.-1], which suggest that the mathematical model precisely captures the general topology of the conformational potential energy surface. Furthermore, this paper provides insights on the conformational preferences of amino acid diamides through local minima geometries and energy ranges, using the improved mathematical model. The proposed mathematical model presents a simpler representation that attempts to provide a framework on building polypeptide models from individual amino acid functions, and consequently, a novel method for rapid but accurate evaluation of potential energies for biomolecular simulations. Key words: potential energy surface, conformational analysis, mathematical modeling. La prediction de la structure tridimensionnelle d'une proteine a partir de sa sequence d'acides amines requiert une parfaite comprehension des forces moleculaires qui influencent le processus de repliement des proteines. Chacune des conformations possibles possede sa propre energie potentielle, laquelle caracterise sa stabilite thermodynamique. Ces connaissances sont necessaires pour la determination des interactions primaires intra et intermoleculaires, de maniere a pouvoir reduire la dimensionnalite du probleme et creer une representation relativement simple du systeme. L'etude de ce probleme a l'aide de methodes de chimie quantique, bien que produisant des resultats exacts, necessite aussi des ressources informatiques considerables. Dans le cadre de la presente etude, nous proposons une fonction d'energie potentielle a deux rotors pour representer les interactions du squelette d'acides amines, par une combinaison lineaire d'une serie de Fourrier et d'un amalgame de fonctions gaussiennes. Nous avons applique cette fonction a l'approximation des surfaces d'energie potentielle (SEP) de type Ramachandran des 20 acides amines d'un diamide. Les resultats ont produit un ecart moyen quadratique de 2,38 kJ*[mol.sup.-1], ce qui laisse supposer que ce modele mathematique represente bien la topologie generale de sa surface d'energie potentielle conformationnelle. De plus, cet article fournit des informations sur les conformations preferentielles de diamides d'acides amines grace a la geometrie des minima locaux et aux intervalles energetiques obtenus au moyen de ce modele mathematique ameliore. Le modele mathematique que nous pro-posons offre une representation simplifiee en vue d'etablir un cadre pour la construction de modeles de polypeptides a partir des fonctions des acides amines qui le composent et, par consequent, constitue une nouvelle methode pour l'evaluation rapide et exacte des energies potentielles aux fins de modelisation de biomolecules. [Traduit par la Redaction] Mots-cles : surface d'energie potentielle, analyse conformationnelle, modelisation mathematique., Introduction Proteins, which are assembled from 20 amino acids, are machines and building blocks of living cells. The macromolecules are vital for structure, function, and regulation of various biological processes. [...]

Nanohydrogels were prepared from copolymerization of acrylamido-2-methylpropane sulfonic acid (AMPS) and acrylamide (AAm) in presence of sodium lauryl sulfate (SLS). The direct ionizing radiation of [gamma]-rays was used to initiate the copolymerization reaction. The different concentrations of SLS, variable irradiation doses, a fixed total monomer concentration, and comonomer composition were used. The features of nanohydrogel were characterized by Fourier transform infrared, thermal gravimetric analysis, and BET surface area analysis of porosity. The results confirmed the structure formation of copoly(AMPS/AAm) nanohydrogels. The SLS concentration affects clearly the pore characteristics and nanoparticle sizes. The nanoparticle and pore size distributions referred to that the pores and nanoparticle formed in wide range of nanoscale. The surface area and pore volume depended basically on the SLS concentration. The gel fraction of nanohydrogels ranged from (98 [+ or -]2.3) to (100 [+ or -]1.5)%. The nanohydrogels were used in in vitro release of 5-fluorouracil (5-FU) at different simulated fluids. The release profile showed a prolonged release of 5FU at two different simulated fluids of pHs of 1.2 for simulated gastric fluid and 7.4 for simulated intestinal fluid. The study demonstrated that copoly(AMPS/AAm) nanohydrogel may serve as a promising material for the sustained release of 5-FU in stomach and colon media., INTRODUCTION A porous hydrogel is a three-dimensional network of a hydrophilic polymer that absorbs a large amount of water either in a very short or a relative long period of [...]

This study examines the selective dispersion of nano-Si02 in polystyrene (PS) and polyamide 6 (PA6) blends. With the coupling assistance of 3-methacryloylpropyl trimethoxysilane (MPS), nano-Si[O.sub.2] surfaces are grafted with PS chains of different molecular weights (Si[O.sub.2]-MPS-PS) or reactive random copolymer of styrene (St) and 3-isopropenyl-[alpha],[alpha]'-dimethylbenzene isocyanate (TMI) to produce Si[O.sub.2]-MPSP-(St-co-TMI). The isocyanate groups of the reactive copolymer can react with the terminal group of the PA6 to form a graft copolymer, which helps in controlling the location of nano-Si[O.sub.2] between the PS and PA6 phases. Field-emission scanning electron microscopy imaging combined with the rheological method was used to investigate the location and dispersion of nano-Si[O.sub.2], as well as the morphology of the PS/PA6 blends, at low nano-Si[O.sub.2] loading. Compared with pristine Si[O.sub.2], the modified Si[O.sub.2] with different chain lengths adjusted the PA6 phase with refined size and narrow size distribution because of the strong interaction with both phases. The Si[O.sub.2]-MPS-PS with appropriate length is the most effective. The use of nano-Si[O.sub.2] along with the reactive compatibilizer provides synergistic effects for improving the compatibilization of PS/PA6 blends., INTRODUCTION Polymer blends with two or more components have gained commercial attention, owing to their superior compositive performance with respect to virgin polymeric materials. However, unfavorable interfacial conditions sometimes render [...]

A comparison about excited state intramolecular proton transfer (ESIPT) mechanism of a new sensor 3-(1,3-benzothiazol-2-yl)-2-hydroxynaphthalene-1-carbaldehyde (3BHC) in polar solvent dimethylformamide (DMF) and nonpolar solvent toluene have been investigated within the frameworkofthe time-dependent density functional theory (TD-DFT) method. The reproduced previous experimental absorption and emission spectra via our calculations reveals the reasonability of the DFT and TD-DFT theoretical level. The staple bond lengths, bond angles, and corresponding infrared vibrational spectra demonstrate that the intramolecular hydrogen bond of 3BHC should be strengthened in both polar DMF and nonpolar toluene. Two kinds of ESIPT mechanisms for different solvents have been put forward; there is alow potential barrier in the ESIPT process in the DMF solvent, whereas there is almost a nonbarrier for the ESIPT process in the toluene solvent. Hence, we could conclude that the ESIPT process of 3BHC sensor is more likely to occur in the nonpolar solvent upon the photoexcitation, based on which, the excited state behavior of 3BHC could be controlled. Key words: hydrogen bond, ESIPT, potential energy curves. Nous avons effectue une comparaison portant sur le mecanisme de transfert de proton intramoleculaire dans l'etat excite (TPIEE) d'un nouveau capteur, le 3-(1,3-benzothiazol-2-yl)-2-hydroxynaphtalene-1-carbaldehyde (3BHC), dans un solvant polaire, le dimethylformamide (DMF), et dans un solvant non polaire, le toluene, dans le cadre d'une methode en theorie de la fonctionnelle de la densite dependante du temps (TD-DFT). La reproduction par nos calculs des spectres d'emission et d'absorption obtenus d'abord experimentalement temoignede lavraisemblance du niveau theorique de la DFTde laTD-DFT. Les longueurs et les angles des liaisons caracteristiques, ainsi que les spectres vibrationnels infrarouges correspondants, demontrent que la liaison hydrogene intramoleculaire du 3BHC devrait etre renforcee tant dans le DMF, qui est polaire, que dans le toluene, qui est non polaire. Nous avons propose l'existence de deux types de mecanismes de TPIEE distincts pour les deux solvants du fait que le processus de TPIEE presente une faible barriere de potentiel dans le DMF, tandis que celle-ci est presque inexistante dans le toluene. Par consequent, nous pouvons conclure que la photoexcitation est plus susceptible d'induire le processus de TPIEE du capteur 3BHC dans un solvant non polaire, et que ces conditions permettent de moduler le comportement du 3BHC dans l'etat excite. [Traduit par la Redaction] Mots-cles : liaison hydrogene, TPIEE, courbes d'energie potentielle., Introduction Proton transfer (PT), a kind of ubiquitous elementary process, is one of the most significant reactions in acid--base biological and chemical dynamics. (1-3) In general, the PT process occurs [...]

In this paper, palladium--DABCO complex supported on magnetic nanoparticles was successfully used as a new magnetically recoverable heterogeneous catalyst for the synthesis of arylphosphonates via P-arylation of different types of aryl halides (aryl iodides/bromides/chlorides and benzene boronic acid/sulfonate), with phosphite esters (triethyl/triphenyl/tri-iso-propyl/diethyl/diphenyl/di-iso-propyl phosphite) in neat water without using any additive. The heterogeneous catalyst was easily isolated from the reaction mixture by an external magnet and reused five times without significant degradation in its activity. Key words: arylphosphonates, Hirao reaction, heterogeneous catalyst, magnetic nanoparticles, palladium. Resume : Dans le present article, nous presentons l'emploi d'un nouveau catalyseur heterogene a base d'un complexe de palladium--DABCO sur support de nanoparticules magnetiques permettant la recuperation du catalyseur par magnetisme. Nous avons utilise ce catalyseur dans la synthese d'arylphosphonates par P-arylation de differents types d'halogenures d'aryles (iodures/bromures/chlorures d'aryles, acide benzeneboronique et benzenesulfonate) en faisant reagir des esters de phosphite (phosphite de triethyle/triphenyle/triisopropyle/diethyle/diphenyle/diisopropyle) dans l'eau pure sans aucun additif. Nous avons facilement isole le catalyseur heterogene du melange reactionnel a l'aide d'un aimant externe et l'avons reutilise cinq fois sans perte significative d'activite. [Traduit par la Redaction] Mots-cles : arylphosphonates, reaction d'Hirao, catalyseur heterogene, nanoparticules magnetiques, palladium., Introduction Arylphosphonates are valuable compounds in a variety of fields, especially as intermediates in organic synthesis, (1) in the preparation of biologically active materials, (2) and in designing fuel cell [...]

Base-catalyzed Michael addition of nitroalkane to conjugated nitroalkene suffers serious practical difficulties due to the formation of oligomeric byproduct. Given its importance for synthesis of pharmacologically relevant organic compounds, a scalable synthesis of 1,3-dinitroalkane is developed by addition of nitroalkane to nitroalkene in aqueous phosphate buffer at pH 7.0 with no added traditional base catalyst. Key words: 1,3-dinitroalkanes, Michael addition, phosphate buffer, base free, diastereoselective. La reaction de Michael catalysee par une base pour effectuer l'addition d'un nitroalcane a un nitroalcene conjugue pose des difficultes pratiques majeures en raison de la formation de sous-produits oligomeriques. Etant donne son importance pour la synthese de composes possedant une activite pharmacologique, nous avons elabore une synthese de 1,3-dinitroalcanes adaptable a grande echelle qui procede par addition d'un nitroalcane a un nitroalcene dans un tampon aqueux de phosphate a pH 7,0, sans catalyseur basique. [Traduit par la Redaction] Mots-cles: 1,3-dinitroalkanes, addition de Michael, tampon phosphate, sans base, diastereoselective., Introduction In organic synthesis, methods for the development of carbon-carbon bond forming reactions are considered as the cornerstone of building complex molecular architechture. (1-5) Many of such C-C bond forming [...]

A kinetic study on [S.sub.N]Ar reactions of 1-aryloxy-2,4-dinitrobenzenes (1a-1h) with a series of cyclic secondary amines in 80 mol% water - 20 mol% DMSO at 25.0 [+ or -] 0.1 [degrees]C is reported. The plots of [k.sub.obsd] versus amine concentration curve upward except for the reactions of substrates possessing a strong electron-withdrawing group in the leaving aryloxide with strongly basic piperidine. The curved plots indicate that the reactions proceed through both uncatalytic and catalytic routes. Linear Bronsted-type plots have been obtained for the uncatalyzed and catalyzed reactions of 1-(4-nitrophenoxy)-2,4-dinitrobenzene (1a) with [[beta].sub.nuc] = 0.84 and 0.78, respectively. The Yukawa-Tsuno plot for the uncatalyzed reactions of 1a-1h with piperidine results in an excellent linear correlation with [rho] = 1.66 and r = 0.31. In contrast, rate constants for catalyzed reactions are independent of the electronic nature of the substituent in the leaving group. The current [S.sub.N]Ar reactions have been proposed to proceed via a zwitterionic intermediate (MC[+ or -]) that partitions to products through uncatalytic and catalytic routes. The catalyzed reaction from MC[+ or -] has been concluded to proceed through a concerted mechanism with a six-membered cyclic transition state ([TS.sub.cycl]) rather than via a stepwise pathway with a discrete anionic intermediate ([MC.sup.-]), the traditionally accepted mechanism. Medium effects on the reactivity and reaction mechanism are discussed. Particularly, hydrogen bonding of the amines to water precludes formation of kinetically significant dimers found in some aprotic solvents; no explicit role for water in the catalytic transition state is required or proposed. The specific stabilization of the leaving aryloxides substituted with strong electron-withdrawing groups accounts for the lack of the catalytic pathway in these systems (1a-1c) with piperidine nucleophile. Key words: [S.sub.N]Ar reaction, Bronsted-type plot, Yukawa-Tsuno plot, zwitterionic intermediate, six-membered cyclic transition state. Resume : Nous presentons une etude cinetique des reactions [S.sub.N]Ar de 1-aryloxy-2,4-dinitrobenzenes (1a-1h) avec une serie d'amines secondaires cycliques dans un melange a 80 mol% eau - 20 mol% DMSO a 25,0 [+ or -] 0,1 [degrees]C. Les courbes de [k.sub.obsd] representees en fonction de la concentration d'amine s'incurvent vers le haut, sauf celles des reactions de substrats dont le groupe partant aryloxyde presente un substituant fortement electroattracteur avec la piperidine, une amine fortement basique. Les traces courbes indiquent que les reactions s'effectuent a la fois par des voies catalytiques et non catalytiques. Nous avons obtenu des courbes de type Bronsted lineaires pour les reactions non catalysee et catalysee du 1-(4-nitrophenoxy)-2,4-dinitrobenzene (1a), dont les coefficients [[beta].sub.nuc] sont de 0,84 et 0,78 respectivement. La courbe de Yukawa-Tsuno pour la reaction non catalysee des composes 1a-1h avec la piperidine presente une excellente correlation lineaire, dont les parametres [rho] = 1,66 et r = 0,31. En revanche, les constantes de vitesse des reactions catalysees sont independantes de la nature electronique du substituant present sur le groupe partant. Nous avons pose l'hypothese que les reactions [S.sub.N]Ar en question procedent par un intermediaire zwitte-rionique (MC[+ or -]) qui se partage en produits par des voies catalytiques et non catalytiques. Nous avons conclu que la reaction catalytique de l'intermediaire MC[+ or -] s'effectue via un mecanisme concerte en passant par un etat de transition cyclique a six membres ([ET.sub.cycl]) plutot que via un mecanisme sequentiel, passant par un intermediaire anionique discret (MC), qui est le mecanisme traditionnellement admis. Nous abordons les effets du milieu sur la reactivite et le mecanisme de reaction. Notamment, les liaisons hydrogene entre les amines et les molecules d'eau empechent la formation de dimeres, favorable sur le plan cinetique, qui est observee dans certains solvants aprotiques; aucun role explicite de l'eau dans l'etat de transition de la voie catalytique n'est necessaire ni n'est propose. L'absence de la voie catalytique dans la reaction des systemes (1a-1c) avec la piperidine comme nucleophile s'explique par la stabilisation specifique des groupes partants aryloxydes portant des substituants fortement electroattracteurs. [Traduit par la Redaction] Mots-cles : reaction [S.sub.N]Ar, courbe de type Bronsted, courbe de Yukawa-Tsuno, intermediaire zwitterionique, etat de transition cyclique a six membres., Introduction In the toolkit of the synthetic organic chemist involved in the design and preparation ofnew aromatic compounds, nucleophilic aromatic substitution on electron-deficient substrates is a versatile, even essential, implement. [...]

Abstract: Reaction between EuCl3 and the ligand 1,3-di(thien-2-yl)propane-1,3-dione (L) leads to luminescent coordination compounds [Eu[L.sub.3][(EtOH).sub.2]](1), [Eu[L.sub.2][(i-PrOH).sub.4]]Cl (2) and [Eu[L.sub.3]([(i-PrOH).sub.2]](3), isolated as single crystals in high yield (70%-95%). The Eu/[beta]-diketonate ratio [...]

Abstract: The effects of solvation on iron salts has been studied by in situ X-ray absorption spectroscopy (XAS). It was seen that the solvated iron is significantly different from the [...]

Abstract: Glass-ceramic composite materials are being investigated for numerous applications (i.e., textile, energy storage, nuclear waste immobilization applications, etc.) due to the chemical durability and flexibility of these materials. Borosilicate [...]

Abstract: This article reports the comparison of different chemical methods to produce graphite-based particles with varying degrees of oxidation, as well as graphene oxide (GO) and pristine graphite (PG). Detailed [...]

Abstract: The present theoretical and experimental results in the literature for formic acid (HCOOH) oxidation into CO on Pd(111) cannot rationalize the well-known, easy CO poisoning. The present study reexamines [...]

Abstract: Poly and mono sulfonamide ligands were successfully used for the stabilization of palladium nanoparticles. The prepared nano catalysts that appeared to be heterogeneous and novel were characterized with various [...]

Abstract: An efficient and rapid method is described for the reductive Claisen rearrangement of different propargyloxyanthraquinones to anthra[1,2-b]furan-6,11-diones for first time using iron powder in a mixture of two ionic [...]

Abstract: Ionic liquids (ILs) are used in lignocellulosic biomass (LCB) pretreatment because of their ability to disrupt the extensive hydrogen-bonding network in cellulose and hemicellulose, and thereby decrease LCB recalcitrance [...]

The adsorption of vanadium(V) and 8-hydroxyquinoline-5-sulfonic acid (HQS) on polyacrylonitrile fiber disks filled with an AV-17 (PANV-AV-17) anion exchanger is studied by diffuse reflection spectroscopy. Vanadium(V) at pH 5-7 is adsorbed on PANV-AV-17; when a HQS solution is applied to the disk, a yellowish green complex compound formed, which changed color to almost black after the treatment of the disk with a HCl solution. The presence of sulfo groups in the HQS molecule ensures the preconcentration of the reagent on PANV-AV-17 disks with the registration of an analytical signal after the treatment of the disk with NaV[O.sub.3] and 0.1 M HCl solutions. A linear dependence of the analytical signal is observed in the HQS concentration range of 1-10 [micro]g/mL. The presence of 20-fold amounts (by weight) of 8-hydroxyquinoline (HOQ) does not interfere with the determination. When ascorbic acid is applied to the disk with a vanadium(V)-HQS-HCl complex, the color changes from black to green. A test method for the determination of ascorbic acid is proposed. 8-Hydroxyquinoline can be determined by the intrinsic color of the adsorbate on PANV-KU-2 in the range of concentrations of HOQ solution in two drops 5-100 [micro]g. Keywords: diffuse reflection spectroscopy, vanadium, PANV-AV-17, PANV-KU-2, 8-hydroxyquinoline, 8-hydroxyquinoline-5-sulfonic acid, ascorbic acid DOI: 10.1134/S1061934817070115, The development of rapid methods for the determination of metal ions, anions, and organic compounds in various objects remains an urgent task. IN determining a number of organic substances (phenol [...]