Influence of guests and protonation on the conformation of N,N′-dipyridyl-bis-aza-18-crown-6

Crystallisation of the sodium perchlorate adduct of N,N^′-dipyridyl-bis-aza-18-crown-6 from acidic aqueous conditions yielded [(H₃O)(N,N^′-dipyridyl-bis-aza-18-crown-6)][ClO₄] and [Na·N,N^′-dipyridyl-bis-aza-18-crown-6]₂ [(H⁺)₂N,N^′-dipyridyl-bis-aza-18-crown-6][ClO₄]₄·2H₂O. The conformations of crown ethers were significantly influenced by incorporation of an H₃O⁺ or sodium ion, or protonation of the amino nitrogen atoms resulting in three different structures for the macrocycle.     

Electrochemical study of the stability of the electron-donor—acceptor (EDA) complex between N,N,N′,N′-tetramethyl-p-phenylendiamine and m-dinitrobenzene in acetonitrile

The stability constant of the EDA complex between N,N,N′,N′-tetramethyl-p-phenylendiamine and m-dinitrobenzene in acetonitrile has been studied by cyclic voltammetry and potentiometric titration at constant finite current. For comparison, spectral measurements were made. The spectroscopic techniques allowed us to assume the formation of a 1:1 EDA complex of which stability in acetonitrile is lower than that previously reported in chloroform. This solvent effect is expected for such weak complexes. The electrochemical techniques give a higher value of the stability constant in similar conditions. The possible causes of the discrepancies are discussed. However, the enthalpy and entropy values for the process closely agree in both electrochemical and spectroscopic methods. This is good evidence that both techniques are accounting for the same type of interaction. The electrochemical techniques, and particularly cyclic voltammetry, seem to be fast and sensible methods to study EDA complex interactions in polar aprotic solvents.     

Evaluation of the Hydrophilic Complexant N,N,N’,N’-tetraethyldiglycolamide (TEDGA) and its Methyl-substituted Analogues in the Selective Am(III) Separation

ABSTRACT

N,N,N’,N’-tetraethyldiglycolamide (TEDGA) is used in the French EXAm (extraction of americium) process to separate Am(III) from Cm(III) and Ln(III). In this study, the complexation behavior of TEDGA towards actinides(III) and lanthanides(III) was compared to its methyl-substituted derivatives Me-TEDGA and Me₂-TEDGA under experimental conditions applying to the EXAm process. Using the EXAm solvent, 0.6 mol/L N,N’-dimethyl-N,N’-dioctyl-hexylethoxymalonamide (DMDOHEMA) and 0.45 mol/L bis(2-ethylhexyl)-phosphoric acid (HDEHP), An(III) and Ln(III) distribution ratios increase in the order TEDGA < Me-TEDGA < Me₂-TEDGA. This is explained by differences in the strength of complexation in the aqueous phase: Conditional stability constants for the formation of [Cm(DGA)_x]³⁺ complexes decrease in the order TEDGA > Me-TEDGA > Me₂-TEDGA, as shown by time-resolved laser fluorescence spectroscopy (TRLFS). TRLFS measurements verified the exclusive existence of [Cm(DGA)₃]³⁺ complexes in the aqueous phase. Both the homoleptic [Cm(DMDOHEMA)_n]³⁺ and the heteroleptic [Cm(DGA)_x(DMDOHEMA)_y]³⁺ complexes were detected in the organic phase, as postulated in the literature.^[14]     

Extraction Behavior of Actinides and Metal Ions by the Promising Extractant,N,N,N′,N′-Tetraoctyl-3,6-dioxaoctanediamide (DOODA)

Abstract

The extraction of actinides, fission products, some non-nuclear elements, and nitric acid by N,N,N′,N′-tetraoctyl-3,6-dioxaoctanediamide (DOODA-C₈) in dodecane was extensively studied. Also studied was the extraction of HNO₃ and Nd(III) by the tetradodecyl analog of DOODA-C₈ in dodecane. Both extractants contain two ether oxygen atoms in the backbone chain carrying the two amide groups and can thus act as tetradentate ligands. The extractability of actinides decreases in the order Pu(IV) > U(VI), Am(III) > Np(V) in the extraction from nitric acid and Pu(IV) > Am(III) >> U(VI) in the extraction from perchloric acid. Ions of di-, tri-, tetra-, hexa-, and heptavalent metals strongly differ in the extractability by DOODA-C₈ but, except for lanthanides(III), there is no visible correlation of their distribution ratios with ionic radii. Due to the efficient extraction of actinides, weak extraction of fission products, and sufficient extraction capacity, DOODA-C₈ is a promising extractant for the recovery of minor actinides from high-level radioactive wastes.     

Copolymerization of styrene and methyl methacrylate mediated by iron wire/N,N,N′,N′-tetramethyl-1,2-ethanediamine as catalyst in the presence of air

Random copolymers of P(MMA-co-styrene) were synthesized via single electron transfer-living radical polymerization (SET LRP) at 25 °C in N,N-dimethylformamide (DMF) and benzene using CCl₄ as initiator and Fe(0) wire/N,N,N′,N′-tetramethyl-1,2-ethanediamine (TMEDA)/hydrazine (NH₂NH₂) complexes as catalyst in the presence of air. Fe(0) wire-mediated single electron transfer-living radical copolymerization of MMA and styrene represented a robust and versatile technique to synthesize the well-defined copolymers. The copolymerization rate was faster in DMF than in benzene, as determined by the apparent rate constants. The results showed that the copolymerization followed first-order kinetics model in the presence of polar DMF and non-polar benzene. The molecular weights increased linearly with the increase of monomer conversion with a narrow polydispersity index when the conversion was beyond 25 %. The polarity and the quantity of solvent had significant effects on the polymerization, and the apparent rate constants were 1.28 × 10^?4, 1.21 × 10^?4, and 9.23 × 10^?5 s^?1 in the order of DMF amount, 5, 10, and 15 mL. The conversion increased from 29.3 to 48.5 % and the polydispersity index (PDI) changed from 1.24 to 1.21 with [CCl₄]₀/[TMEDA]₀ molar ratio changing from 1:0.5 to 1:5. The chain extension experiment demonstrated that the copolymerization exhibited a living characteristic.     

Accumulation and apparent recovery of N,P and K after the incorporation of gliricidia and manure in intercropping during the cultivation of corn–cowpea–cotton

Fertilization with manure is widely adopted by farmers in the semiarid region of northeastern Brazil, although the quantity of available manure is limited. Thus, among other alternatives, gliricidia has been used as an additional source of organic fertilizer. The objective of this study was to evaluate the accumulation and apparent recovery of N, P and K after using different forms of gliricidia and manure application in the intercropping of corn, cowpea and cotton in three crop cycles in the semi-arid northeast region of Brazil. The following treatments were used: gliricidia incorporated into the soil before planting; gliricidia spread on the surface of the soil at 45 days after planting; manure and gliricidia incorporated into the soil before planting; manure incorporated into the soil before planting and gliricidia spread on the surface of the soil at 45 days after planting; manure incorporated into the soil before planting; and no addition of organic fertilizer (control). Accumulations followed the same pattern as biomass production but differed greatly from the concentrations. Low apparent recoveries were obtained in the first and second cycles, and high apparent recoveries were obtained in the third cycle. The nutrient balances indicated that the incorporation of gliricidia before planting or spread on the surface does not meet crop needs. The incorporation of manure as well as manure and gliricidia when applied on the surface, were able to meet growth needs and maintain soil fertility.     

Comparison of Hydrometallurgical Parameters of N,N‐Dialkylamides and of Tri‐n‐Butylphosphate

Straight‐chain N,N‐dihexyloctanamide (DHOA) and branched‐chain N,N‐di(2‐ethylhexyl)isobutyramide (D2EHIBA) have been identified as promising alternatives to tri‐n‐butylphosphate (TBP) for the reprocessing of spent uranium based fuels, and selective extraction of ²³³U from irradiated thorium fuels, respectively. The present work deals with the effects of different hydrodynamic parameters such as viscosity, density, and interfacial tension (IFT) on the phase‐separation time (PST) under uranium and thorium loading conditions. The IFT values have been determined under varying experimental conditions such as the aqueous nitric acid concentration, n‐dodecane purity, ligand concentration, and thorium/uranium loading conditions. These studies have suggested that the quality of n‐dodecane affects the IFT values of different solutions. The IFT values of D2EHIBA changed marginally (23.3 ± 0.9 mNm^?1) against THOREX feed solution for the wide range of D2EHIBA concentration (0.1–1.0 M). However, IFT, viscosity, and PST values increased with uranium loading of 1.1 M DHOA. These studies suggested that a lower phase‐disengagement rate with increased uranium loading was mainly due to the increased viscosity of the loaded 1.1 M DHOA solution.     

A highly active palladium complex catalyst in the synthesis of N,N′-diphenylurea from nitrobenzene,aniline and carbon monoxide

A catalyst system comprising palladium acetate and bidentate bis(diphenylphosphino)alkane ligand of general formula Ph₂P(CH₂)_nPPh₂ (n = 3–5) was highly active in N,N-diphenylurea synthesis from nitrobenzene, aniline and carbon monoxide and showed different reactivity from the system with the more common monodentate triphenylphosphine ligand.     

Synthesis and reactivity of an 2-azabutadiene-based π-conjugated dithioether: Formation of a N,S-ligated molybdenum chelate complex and C,N,S-pincer complexes of palladium and platinum

Nucleophilic attack of sodium isopropylthiolate on 4,4-dichloro-1,1-diphenyl-2-azabuta-1,3-diene [Cl₂CC(H)–NCPh₂}] (1) affords the 2-azabutadiene derivative [(i-PrS)₂CC(H)–NCPh₂] (2). Upon irradiation of Mo(CO)₆ in THF in the presence of 2, the chelate complex cis-[(OC)₄Mo{(i-PrS)₂CC(H)–NCPh₂}] (3) is obtained. Coordination on Mo occurs through the imine nitrogen and a thioether group. Polydentate dithioether 2 acts as N,C,S-pincer ligand after orthometallation reaction with Pd(II) or Pt(II). The molecular structures of 2 and (C,N,S)-[(i-PrS)₂CC(H)–NC(Ph)C₆H₄)PtCl] (4b) have been determined by X-ray diffraction studies.     

Synthesis of N,N′-Dimethyl-N,N′-Dioctyl-3-Oxadiglycolamide and its Extraction Properties for Lanthanides

Abstract

Tetraalkyl-3-oxadiglycolamides show good prospects in nuclear reprocessing because of their complete incinerability. In addition, their degradation products interfere much less in the separation process when compared with organophosphorus extractants. An asymmetric extractant, N,N′-dimethyl-N,N′-dioctyl-3-oxadiglycolamide, has been synthesized by a five-step process. The compound was applied to the extraction of selected lanthanides from nitric acid solutions using chloroform as diluent. Its extraction properties for lanthanides from nitrate media have been described. The distribution ratio of the selected metal ions has been studied as a function of aqueous HNO₃ concentrations, diglycolamide concentration and temperature.     

Experimental Measurement and Correlation of the Solubility of Methyl-acetyl-naphthalene in n-Heptane,n-Octane,and n-Dodecane

1 INTRODUCTION 2-Methyl-6-acetylnaphthalene (2,6-MAN) is a type of white or pale yellow, powdery crystal, with a melting point of 332.15K. It is an important interme- diate[1] used for producing 2,6-naphthalene dicarbox- ylic acid (2,6-NDA), which has very extensive appli- cations in not only the light, electronic, and defense industries, but in many other areas. In particular, 2,6-NDA is an important monomer of liquid crystal polyester material (LCP) and polyethylene naphtha- lene-2…     

A Study of the γ-Radiolysis of N,N-Didodecyl-N′,N′-Dioctyldiglycolamide Using UHPLC-ESI-MS Analysis

Solutions of N,N-didodecyl-N′,N′-dioctyldiglycolamide in n-dodecane were subjected to γ-irradiation in the presence and absence of both an aqueous nitric acid phase and air sparging. The solutions were analyzed using ultra-high-performance liquid chromatography-electrospray ionization-mass spectrometry (UHPLC-ESI-MS) to determine the rates of radiolytic decay of the extractant as well as to identify radiolysis products. The DGA concentration decreased exponentially with increasing dose, and the measured degradation rate constants were uninfluenced by the presence or absence of acidic aqueous phase, or by air sparging. The identified radiolysis products suggest that the bonds most vulnerable to radiolytic attack are those in the diglycolamide center of these molecules and not in the side chains.     

Dependence of water sorption-desorption characteristics of N,N′-methylene-bis-acrylamide and tetraethyleneglycol diacrylate-crosslinked polyacrylamides on crosslinking

Summary Hydrophilic monomers such as acrylamide (AA) when crosslinked with highly hydrophilic flexible tetraethyleneglycol diacrylate (TEGDA) and N,N-methylene-bis-acrylamide (NNMBA) of intermediate polarity and hydrophilicity provides highly water swellable hydrogels. These water-swellable but water insoluble macromolecules possess a number of physicochemical properties useful for applications in biomedical and other technological fields. This paper describes the swelling/deswelling characteristics and the ability for water retention of these polymers in different compositions. Water sorption in these crosslinked polyacrylamides is dependent on a number of variables of polymer synthesis.     

New Trends and Future Opportunities in the Enzymatic Formation of C−C,C−N,and C−O bonds

Organic chemistry provides society with fundamental products we use daily. Concerns about the impact that the chemical industry has over the environment is propelling major changes in the way we manufacture chemicals. Biocatalysis offers an alternative to other synthetic approaches as it employs enzymes, Nature's catalysts, to carry out chemical transformations. Enzymes are biodegradable, come from renewable sources, operate under mild reaction conditions, and display high selectivities in the processes they catalyse. As a highly multidisciplinary field, biocatalysis benefits from advances in different areas, and developments in the fields of molecular biology, bioinformatics, and chemical engineering have accelerated the extension of the range of available transformations (E. L. Bell et al., Nat. Rev. Meth. Prim. 2021 , 1, 1–21). Recently, we surveyed advances in the expansion of the scope of biocatalysis via enzyme discovery and protein engineering (J. R. Marshall et al., Tetrahedron 2021 , 82, 131926). Herein, we focus on novel enzymes currently available to the broad synthetic community for the construction of new C−C, C−N and C−O bonds, with the purpose of providing the non-specialist with new and alternative tools for chiral and sustainable chemical synthesis.     

15N solid state NMR study of the reactions of propane or propene, 15NO and oxygen on Na‐, H‐, and CuZSM‐5

Ni- and Co-based catalysts derived from NiAl- and CoAl-layered double hydroxides were tested in four kinds of reactions of methanol, namely decomposition of methanol (DCM), partial oxidation of methanol (POM), steam reforming of methanol (SRM), and oxidative steam reforming of methanol (OSRM), for the purpose of H₂ production for fuel cells. H₂, CO and/or CO₂ were the predominant products with minor amounts of dimethyl ether (DME) and CH₄ depending on the reaction temperature. Among the four kinds of reactions tested, the OSRM reaction was found to be more effective in terms of MeOH conversion and H₂ selectivity over these catalysts. Higher selectivity of H₂ and CO₂ with only traces of CO could be obtained at about 100% methanol conversion around 300 °C in the OSRM reaction over the catalyst derived from CoAl-LDH. Substitution of a part of Al by Sn in the NiAl- and CoAl-LDH systems was found to be inhibiting the methanol conversion. On the other hand, the selectivities to DME and CH₄ were declined with a consequent increase in the selectivity to H₂. In addition, considerable amount of formaldehyde was also noticed, especially over the catalyst derived from CoAlSn-LDH at lower reaction temperatures. The observed difference in the catalytic performance upon Sn incorporation was attributed to an improved redox capability of the Ni- and Co-based oxide catalysts, as determined by temperature-programmed reduction (TPR) experiments. This revised version was published online in July 2006 with corrections to the Cover Date.     

A novel catalyst system for the synthesis of N,N′-Methylenebisacrylamide from acrylamide

N,N′-Methylenebisacrylamide (MBAA), which is an important raw material in a widely industrial area, was synthesized using convenient catalysts. The synthesized monomer was fully characterized by the elemental analysis, fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), ¹H-NMR, ¹³C-NMR, GC/MS, and high performance liquid chromatography (HPLC) analysis. Six different homogeneous and heterogeneous catalysts were used to obtain maximum monomer yield. The MBAA was obtained with 95% yield by using Cu(II) catalyst containing carboxylate groups ligands.     

Effects of Zn, Cu, and K Promoters on the Structure and on the Reduction, Carburization, and Catalytic Behavior of Iron-Based Fischer–Tropsch Synthesis Catalysts

Zn, K, and Cu effects on the structure and surface area and on the reduction, carburization, and catalytic behavior of Fe–Zn and Fe oxides used as precursors to Fischer–Tropsch synthesis (FTS) catalysts, were examined using X-ray diffraction, kinetic studies of their reactions with H₂ or CO, and FTS reaction rate measurements. Fe₂O₃ precursors initially reduce to Fe₃O₄ and then to metallic Fe (in H₂) or to a mixture of Fe_2.5C and Fe₃C (in CO). Zn, present as ZnFe₂O₄, increases the surface area of precipitated oxide precursors by inhibiting sintering during thermal treatment and during activation in H₂/CO reactant mixtures, leading to higher FTS rates than on ZnO-free precursors. ZnFe₂O₄ species do not reduce to active FTS structures, but lead instead to the loss of active components; as a result, maximum FTS rates are achieved at intermediate Zn/Fe atomic ratios. Cu increases the rate of Fe₂O₃ reduction to Fe₃O₄ by providing H₂ dissociation sites. Potassium increases CO activation rates and increases the rate of carburization of Fe₃O₄. In this manner, Cu and K promote the nucleation of oxygen-deficient FeO _x species involved as intermediate inorganic structures in reduction and carburization of Fe₂O₃ and decrease the ultimate size of the Fe oxide and carbide structures formed during activation in synthesis gas. As a result, Cu and K increase FTS rates on catalysts formed from Fe–Zn oxide precursors. Cu increases CH₄ and the paraffin content in FTS products, but the additional presence of K inhibits these effects. Potassium titrates residual acid and hydrogenation sites and increases the olefin content and molecular weight of FTS products. K increases the rate of secondary water–gas shift reactions, while Cu increases the relative rate of oxygen removal as CO₂ instead of water after CO is dissociated in FTS elementary steps. Through these two different mechanisms, K and Cu both increase CO₂ selectivities during FTS reactions on catalysts based on Fe–Zn oxide precursors.     

Synthesis and properties of polysiloxane containing N,N′-bis(diphenylsilyl)tetraphenylcyclodisilazane

A new kind of polysiloxane containing N,N′-bis(diphenylsilyl)tetraphenylcyclodisilazane was prepared by the anionic polymerization with a “seed solution” as initiator. The synthesis of monomers N,N′-bis(hydroxydiphenylsilyl)tetraphenylcyclodisilazane (BHPTPC), N,N′-bis(chlorodiphenylsilyl)tetraphenylcyclodisilazane (BCPTPC), and 1,3-dichloro-1,1,3,3-tetraphenyldisilazane (DCTPS) are all reported in this study. The synthesized polysiloxane containing N,N′-bis(diphenylsilyl)tetraphenylcyclodisilazane was characterized by ¹H–NMR, ²⁹Si–NMR, gel permeation chromatography (GPC), and intrinsic viscosity. The thermal stability of the polysiloxane was studied by isothermal gravimetric analysis (IGA). The results demonstrated that the synthesized polysiloxane containing N,N′-bis(diphenylsilyl)tetraphenylcyclodisilazane had excellent thermal stability. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 929–933, 2001