N-methylmorpholine-N-oxide Research Articles

Cellulose micro-dissolution by N-methylmorpholine N-oxide as a facile route for magnetic functional cotton textiles

In this work, an environmental micro-dissolution method to prepare Fe3O4 NPs@cotton composite fabrics without using binders is reported. The controlled N-methylmorpholine N-oxide (NMMO) treatment can micro-dissolve superficial layers of fibers through the strong hydrogen bonding force. The micro-dissolved superficial layers themselves can work like glue to physically adhere surrounding Fe3O4 NPs and then these Fe3O4 NPs can be embedded onto the layers. In the subsequent heating treatment, the micro-dissolved superficial layers would physically re-coagulate, immobilizing Fe3O4 NPs onto fibers’ surface. The as-obtained Fe3O4 NPs@cotton composite fabrics were systematically characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Additionally, through vibrating sample magnetometry tests, the Fe3O4 NPs@cotton fabrics exhibit para-magnetism, and the saturation magnetization can remain up to 90% after 20 washing cycles. Thermal gravimetric analysis and moisture absorption tests show that there are no obvious influences on thermal stability and moisture absorption capability of cotton fabrics. Even noticeable enhancements in mechanical properties can be observed.

A STUDY OF SUSTAINABLE COLORATION OF LYOCELL FABRICS USING EXTRACTS OF TROPICAL ONION SKINS

Lyocell is considered as a new fiber that represents a milestone in the development of environmentally sustainable textiles. Lyocell is spun from wood pulp cellulose via a green chemical process with NMMO (N-methylmorpholine-N-oxide) solvent. Following the concept of lower the environmental impact of fashion clothing, this study aims to determine the suitable natural dyes recipes with the color extracting from tropical onion skins. Colorants were extracted by dissolving crushed dried onion skins with boiled in water at 100ºC for 20-25 minutes. The ratio of extracting and dyeing are 1:25 and 1:30 respectively. The optimal dyeing condition was found out at 80ºC, 45 minutes with 75% v/v. In addition, a variety of the most commonly used mordants including Potassium aluminum sulfate, Copper (II) sulphate and Iron (II) sulphate were used for mordanting in order to compare the differently mordanted and unmordanted dyed fabrics via color strength (K/S) and CIE L*a*b* color values. It was found that mordant type had an effect on color strength and the color coordinates of fabric dyed with onion skin, which can supply variety of color choices for the same colorants.

Highly efficient oxidation of alcohols catalyzed by Ru(II) carbonyl complexes bearing salicylaldiminato ligands

Reaction of Ru3(CO)12 with 2.0 equiv of RN = CH(3,5-tBu2C6H2OH) (R = C6H5, L1; R = 4-MeC6H4, L2; R = 4-OMeC6H4, L3; R = 4-ClC6H4, L4; R = 4-BrC6H4, L5; R = 4-CF3C6H4, L6) in refluxing xylene afforded the corresponding bis-chelate Ru(II) complexes 1a–1f [RN = CH(3,5-tBu2C6H2O)]2Ru(CO)2 and one of the imine bonds reduced complexes {[RN = CH(3,5-tBu2C6H2O)]-[RNH-CH2(3,5-tBu2C6H2O)]}Ru(CO)22a–2f. All the ruthenium complexes were fully characterized by NMR, IR and elemental analysis. In addition, the structures of complexes 1a–1f, 2b, 2d and 2f were further confirmed by single-crystal X-ray diffraction. When activated with N-methylmorpholine-N-oxide (NMO), these Ru complexes displayed high catalytic activities toward oxidation of both 1° and 2° alcohols. For most cases, the reaction can complete within 1 h in refluxing CH3CN.

Parent Cyclopentadienyl Ruthenium(II) Chloride Synthon: Derivatization to CpRu Amido, Imido, and Oxo Complexes

The complex salt [CpRu(η6-C10H8)][(CpRu)2(μ-Cl)3] ([1][2]) was synthesized and found to be a useful CpRuCl synthon. The ions [1]+ and [2]− cleanly comproportionate into monomeric CpRuCl(L)2 complexes with liberation of naphthalene upon treatment with donor ligands L such as DMSO, tBuNH2, 1,5-cycloctadiene, and CO. The amine adduct [CpRuCl(NH2tBu)2] allows access to the coordinatively unsaturated dimeric amido complex [CpRu(NHtBu)]2, which is subsequently transformed into the bridging imido complexes [(CpRu)2(μ-NtBu)(μ-CH2)] and [(CpRu)2(μ-NtBu)(μ-CH)]+. The imido methylidyne complex shows enhanced electrophilicity at the methylidyne carbon compared to its bulkier C5Me5 congener and also allows access to a less hindered parent Cp version of the diruthenocarbene ligand in the form of the Ru2Cu μ3-carbido complex [(CpRu)2(μ-NtBu)(μ3-C)Cu{N(SiMe3)2}]. The salt [1][2] also gives a novel tetranuclear μ4-oxo cluster [(CpRuCl)4(μ4-O)] upon oxidation in air or by N-methylmorpholine N-oxide.

The Role of Isobutanol as a Precipitant of Cellulose Films Formed from N-Methylmorpholine N-Oxide Solutions: Phase State and Structural and Morphological Features

The process of film formation including the initial treatment of thin layers of cellulose solutions in N-methylmorpholine N-oxide with isobutanol followed by washing with water is investigated in detail, and the structural and morphological features of the obtained films are examined. The phase state of the N-methylmorpholine N-oxide–isobutyl alcohol system is studied by differential scanning calorimetry and optical interferometry, and a diagram describing the crystalline equilibrium and allowing determination of the temperature–concentration “window” of compatibility of components is constructed. The dependence of viscosity of N-methylmorpholine N-oxide solutions in isobutanol on temperature confirms the phase composition of the system. The process of film formation is modeled by analyzing the diffusion zone of the cellulose solution–isobutyl alcohol system. The IR study of the interaction of N-methylmorpholine N-oxide containing 13.3% water with isobutanol shows that the affinity of isobutanol for water is much higher than that for N-methylmorpholine N-oxide. For this reason, when the spinning solution is brought in contact with isobutanol, the redistribution of water between the interacting components occurs and the structure of the heterogeneous gel-like complex cellulose–N-methylmorpholine N-oxide–isobutanol “is frozen,” as proved by the X-ray diffraction study of the films. Complete removal of the solvent and isolation of cellulose from this film proceed only upon subsequent washing with water. The X-ray diffraction and optical interferometry study of the effect of temperature on the interaction of a hot cellulose solution with cold isobutanol suggests that at room temperature the film obtained from solution contains inclusions of the vitrified N-methylmorpholine N-oxide. Under isothermal conditions (at a temperature of 90°С), the rate of interdiffusion grows appreciably and the solution preserves the homogeneous structure. Thus, the precipitation of cellulose from the bicomponent solvent N-methylmorpholine N-oxide–water upon contact first with isobutanol and then with water proceeds via two stages: initially the system undergoes phase separation and a concentrated solution is formed in the isobutanol-N-methylmorpholine N-oxide blend, from which cellulose precipitates upon interaction with water. When the process of primary interaction of the solution with alcohol is conducted under the conditions of compatibility of isobutanol with N-methylmorpholine N-oxide, a more homogeneous morphology of the films can be obtained.

Cellulose Fibers from Solutions of Bacterial Cellulose in N-Methylmorpholine N-Oxide

Fibers of bacterial cellulose were obtained for the first time from solutions in N-methylmorpholine N-oxide (NMMO) by using the concept of solid-phase dissolution of bacterial cellulose. The mechanism of solid-phase dissolution of bacterial cellulose in NMMO is examined with due regard to the structural and morphological characteristics of native bacterial cellulose. By investigating the structure of the fibers it was possible to reveal the different orientation of the main diffraction planes of the outer shell and inner part of the fiber reflecting the structural aspect of the shell–core morphology. The fibrillar morphology of the fiber was established by scanning electron microscopy. The thermal characteristics of the fibers of bacterial cellulose differ radically from the characteristics of fibers of plant origin in the preponderance of condensation processes that produce exo effects on the thermograms and lead to increase of the carbon residue. The mechanical characteristics of the obtained fibers were characterized.

Determination of N-Methyl morpholine in biomass pretreatment solutions by the ammonia-assisted headspace gas chromatography

An ammonia-assisted headspace gas chromatography (HS-GC) method was developed to determine the N-methyl morpholine (NMM) concentration in biomass fractionation processes. The use of ammonia gas increased the detection sensitivity of NMM, and minimized the interfering effect of other substances during the analysis. Results showed that, by adding 1.5 mL ammonium hydroxide (28–30%, w/w) and a 0.125 mmol of sodium hydroxide into a 4.0 g of sample solution containing 43.3% N-methylmorpholine N-oxide (NMMO), the gas-liquid equilibration of NMM was obtained within 30 min at 80 °C. The optimum sample size and the NMMO content in the sample solutions were 6.0 g and 43.3%, respectively. The present method was proved to be of high precision (RSD = 4.33%), sensitivity (LOQ = 71.9 mg/kg), and with recovery accuracy of 96.0–102%. The present method was rapid, accurate, which will be a powerful tool to optimize the reaction conditions in NMMO-based biomass pretreatment process for enhancing the cost effectivity.

Comparative study of plant and bacterial cellulose pellicles regenerated from dissolved states

Bacterial cellulose (BC), representing the highly purified form of cellulose, possesses better nanofibrous morphology and superior mechanical properties than plant cellulose (PC). However, the regeneration process, which produces intermediate structures, significantly alters the original properties of native cellulose and result in varied structural and physico-mechanical features. Therefore, it is important to estimate the degree of variations in the structures and properties of both PC and BC during their regeneration. Herein, we conducted a detailed comparative study by dissolving BC and PC in N-methylmorpholine N-oxide (NMMO) and synthesizing their regenerated gels, namely regenerated bacterial cellulose (RBC) and regenerated plant cellulose (RPC), respectively. The structural features of BC, PC, RBC, and RPC were comparatively evaluated via field-emission scanning electron microscopy, X-ray diffraction, porosity analyses, as well as analyzed their mechanical, thermal, and liquid-holding capabilities. The results showed inferior mechanical, thermal, and crystalline features of RBC and RPC to their respective counterparts. However, RBC showed better porosity, water absorption capability, and water retention time than RPC. The overall mechanical, thermal, and physiological features of RBC were better than those of RPC. These findings may facilitate the use of RBC in composite synthesis for various applications.

Azoimine Chelated Ruthenium(II)- and Osmium(II)-Carbonyl Complex Catalyzed Alcohol Oxidation Reaction

Arylazoimidazole brings azoimine (-N=N-C=N-) chelating N(azo), N(imine) (abbreviated - N, N/) centres and forms Ru(II) and Os(II) carbonyl complexes. These complexes act as catalysts for the oxidation of alcohols to aldehydes/ketones by tertiary butyl hydro peroxide (ButOOH), hydrogen peroxide (H2O2) and N-methylmorpholine-N-oxide (NMO) as oxygen sources. Different substituted arylazoimidazoles such as 1-alkyl-2-(arylazo)imidazoles (RaaiR/), 1-alkyl-2-(naphthyl-α/β- azo)imidazoles (α/β-NaiR) and (1-alkyl-2-{(o-thioalkyl)phenylazo}imidazole, SRaaiNR/) are used to prepare Ru/Os-CO complexes. Ancillary ligands like hydride (H-), chloride (Cl-), triphenylphosphine (PPh3) are used to monitor the catalytic efficiency of the complexes. Aromatic and aliphatic alcohols like benzyl alcohol, 2-butanol, cyclopentanol, cyclohexanol, 1-phenylethanol, cinnamyl alcohol, diphenylmethanol, are oxidized to the corresponding benzaldehyde, 2-butanone, cyclopentanone, cyclohexanone, phenylacetone, cinamaldehyde, cyclopentanone, benzophenone, respectively. Different physicochemical analyses (FT-IR, UV-Vis, Mass, NMR) suggest that the complexes react with an oxidant to yield high valent ruthenium/osmium-oxo species (RuIV=O; OsIV=O), which is capable of transferring the oxygen atom to alcohols. GC analysis accounts that percentage conversion order is as follows : Cinnamyl alcohol > Cyclohexanol ~ 1-Phenylethanol > Diphenylmethanol > Cyclopentanol > 2-Butanol > Benzyl alcohol. The oxidation efficiency of the oxidant follows the order : NMO > ButOOH > H2O2. RuII complexes are more potent catalysts than OsII complexes. Out of three series of RuII complexes, [RuCl(CO)(SMeaaiNEt)]ClO4 and [RuCl(CO)(SEtaaiNMe)]ClO4 showed highest catalytic efficiency amongst 32 catalysts.

1,2-Azaborine's Distinct Electronic Structure Unlocks Two New Regioisomeric Building Blocks via Resolution Chemistry.

Two new 1,2-azaborine building blocks that enable the broad diversification of previously not readily accessible C4 and C5 ring positions of the 1,2-azaborine heterocycle are developed. 1,2-Azaborine's distinct electronic structure allowed the resolution of a mixture of C4- and C5-borylated 1,2-azaborines. The connection between the electronic structure of C4 and C5 positions of 1,2-azaborine and their distinct reactivity patterns is revealed by a combination of reactivity studies and kinetic measurements that are supported by DFT calculations. Specifically, we show that oxidation by N-methylmorpholine N-oxide (NMO) is selective for the C4-borylated 1,2-azaborine, and the Ir-catalyzed deborylation is selective for the C5-borylated 1,2-azaborine via kinetically controlled processes. On the other hand, ligand exchange with diethanolamine takes place selectively with the C4-borylated isomer via a thermodynamically controlled process. These results represent the first examples for chemically distinguishing a mixture of two aryl mono-Bpin-substituted isomers.

Multifunctional Nanocomposite Cellulose Fibers Doped in Situ with Silver Nanoparticles.

This paper presents a method for the preparation of nanocomposite cellulose fibers doped with silver nanoparticles (AgNPs), as well as the effect of silver nanoparticles on the structure and properties of fibers. The fibers were obtained by an environmentally friendly method using N-Methylmorpholine N-oxide (NMMO) as a solvent, in a non-polluting closed system. Doping with silver nanoparticles was carried out as a direct (in situ) reduction of Ag+ ions in the presence of a stabilizing agent during the preparation of the spinning solution. SEM images of the surface and cross section of the fibers showed that the distribution of nanoparticles in the fibers’ volume was uniform. The fibers exhibited very good antibacterial properties in relation to Staphylococcus aureus, Escherichia coli, Acinetobacter baumannii, and Candida albicans. Flammability analysis showed that the fibers were subjected to a one-stage combustion process and that the silver nanoparticles reduced the heat release rate (HRR) of the fibers by 36%. TG studies showed that the modification of cellulose fibers with silver nanoparticles promoted the formation of mill scale in the combustion of fibers, which was directly related to the reduction of flammability. Tests of the electrical properties showed that the linear resistance of cellulose fibers containing 3 wt % silver was 108 Ω/cm.

Structure of Polyacrylonitrile Fibers Produced from N-Methylmorpholine-N-Oxide Solutions

Structural and morphological evolution of polyacrylonitrile (PAN) samples from starting powder of a ternary copolymer to fibers produced from concentrated solutions of PAN in N-methylmorpholine-N-oxide (NMMO) was studied using x-ray diffraction for the first time. X-ray exposures in transmission and reflection geometries allowed the structures of outer and inner parts of the PAN fibers to be differentiated. It was shown that a shell—core structure formed in the precipitation bath during fiber spinning. A comparison of x-ray diffraction patterns of fibers spun using the NMMO process and industrial samples spun from DMSO and aqueous sodium thiocyanate solutions did not reveal fundamental structural differences.

One-step synthesis of cellooligomer-conjugated gold nanoparticles in a water-in-oil emulsion system and their application in biological sensing.

Monodisperse gold nanoparticles (GNPs) were synthesized in a water-in-oil emulsion system (reverse micelles) composed of 80% N-methylmorpholine N-oxide (NMMO)/20% H2O and dodecane, stabilized with an anionic surfactant: bis(2-ethylhexyl)sulfosuccinate sodium salt. Cellooligomers with a degree of polymerization of 6 or 15 (βGlc6 or βGlc15, respectively), which were labeled at each reducing end group with thiosemicarbazide (TSC) and dissolved in the aqueous NMMO phase, were successfully conjugated to the surfaces of GNPs in situ during spontaneous NMMO-mediated gold reduction. As-synthesized βGlc6-GNPs and βGlc15-GNPs had average diameters of 11.3 ± 2.1 and 10.5 ± 0.7 nm, respectively, while their surface sugar densities were 0.21 and 0.51 chains nm-2, respectively. Concanavalin A (ConA), a lectin that recognizes non-reducing end groups of glucose residues, aggregated with βGlc15-GNPs with higher sensitivity than it did with βGlc6-GNPs, possibly as a result of the sugar density on the GNP surfaces. The aggregates were rapidly re-suspended by adding methyl-β-d-glucopyranoside as a binding inhibitor. Other lectins and proteins showed no interaction with βGlc-GNPs. Therefore, clustering of glucose non-reducing ends on the GNP surfaces via strong intermolecular association of cellooligomers, possibly led to high affinity for ConA. This facile synthesis route to structural carbohydrate-decorated GNPs has potential applications in carbohydrate-nanometal conjugate nano-biosensor development.

Chiral MnIII (Salen) Immobilized on Organic Polymer/Inorganic Zirconium Hydrogen Phosphate Functionalized with 3-Aminopropyltrimethoxysilane as an Efficient and Recyclable Catalyst for Enantioselective Epoxidation of Styrene.

Organic polymers/inorganic zirconium hydrogen phosphate (ZSPP, ZPS-IPPA, and ZPS-PVPA) functionalized with 3-aminopropyltrimethoxysilane were prepared and used to support chiral MnIII (salen) complexes (Jacobsen’s catalyst). Different characterization methods demonstrated that the chiral MnIII (salen) complexes was successfully supported on the surface of the carrier (ZSPP, ZPS-IPPA, or ZPS-PVPA) through a 3-aminopropyltrimethoxysilane group spacer. The supported catalysts effectively catalyzed epoxidation of styrene with m-chloroperbenzoic acid (m-CPBA) as an oxidant in the presence of N-methylmorpholine N-oxide (NMO) as an axial base. These results (ee%, 53.3–63.9) were significantly better than those achieved under a homogeneous counterpart (ee%, 46.2). Moreover, it is obvious that there was no significant decrease in catalytic activity after the catalyst 3 was recycled four times (cons%: from 95.0 to 92.6; ee%: from 64.7 to 60.1). Further recycles of catalyst 3 resulted in poor conversions, although the enantioselectivity obtained was still higher than that of corresponding homogeneous catalyst even after eight times. After the end of the eighth reaction, the solid catalyst was allowed to stand in 2 mol/L of dilute hydrochloric acid overnight, prompting an unexpected discovery that the catalytic activity of the catalyst was recovered again at the 9th and 10th cycles of the catalyst.

Decarboxylative ipso Amination of Activated Benzoic Acids.

In the presence of a bimetallic Pd/Cu system with 1,10-phenanthroline as the ligand and either air or N-methylmorpholine N-oxide as the oxidant, electron-deficient benzoic acids undergo oxidative decarboxylative coupling with unprotected amines. This operationally simple aniline synthesis is widely applicable with respect to the amine and gives good yields, even on multigram scale. The orthogonality of this reaction to other Pd-catalyzed cross-couplings allows the concise synthesis of multisubstituted arenes by sequential C-C, C-Cl, and C-N functionalizations. Mechanistic investigations suggest the intermediacy of a hypervalent Pd species.

Water-induced crystallization and nano-scale spinodal decomposition of cellulose in NMMO and ionic liquid dope

We followed the cellulose structure formation induced by water diffusion into Lyocell dopes based on both N-Methylmorpholine N-oxide (NMMO) and 1,5-diazabicyclo[4.3.0]non-5-ene acetate ([DBNH][OAc], by using scanning simultaneous small- and wide-angle scattering (SAXS-WAXS) experiment along the diffusion gradient. The water content at each point was estimated from the wide-angle scattering profile, giving a binary diffusion constant of the order of 5 × 10−10 m2/sec. In the case of the cellulose solution in NMMO monohydrate, diffraction peaks corresponding to cellulose II appeared concomitantly with the increase in small angle scattering features indicative of nanofibril formation. In the cellulose solution in the ionic liquid, an increase in small angle scattering intensity with the progression of water content appeared at scattering vector q = 0.015 A−1 corresponding to a correlation length of about 40 nm, indicative of nanometric spinodal decomposition preceding the coagulation process, though no crystalline peak appeared in the wide-angle scattering.

Modification of cellulose fibers with inorganic luminescent nanoparticles based on lanthanide(III) ions

This article presents synthesis and properties of the fibers modified with luminescent, inorganic nanoparticles doped with lanthanide(III) ions, i.e. LaF3:Ce3+, Gd3+, Eu3+; CeF3:Tb3+ and CePO4:Tb3+. The fibers with luminescent properties were prepared via so called Lyocell process. This method involves dissolving cellulose in aqueous solution of N-methylmorpholine-N-oxide (NMMO) and a subsequent spinning of the fibers, using a dry-wet method. Thanks to the successful incorporation of the modifier nanoparticles (NPs) into the cellulose matrices, the fibers exhibited bright, multicolor emission upon UV irradiation and good mechanical properties, which allowed further textile processing. This type of fibers, as well as the as-prepared textiles/fabric can be used as an anti-counterfeiting agent for clothes and documents protection.

Cellulose acetate fibers with improved mechanical strength prepared with aqueous NMMO as solvent

Cellulose diacetate (CA) was successfully dissolved in N-methylmorpholine N-oxide aqueous solution (NMMO·H2O). The CA degraded little during the dissolving process and the homogenous CA/NMMO·H2O solutions were obtained even when the concentration was up to 18%. From the rheological behavior of the CA/NMMO·H2O solution, it was found that the viscosity of the solution was lower than that of lyocell solution, which is due to the lower degree of polymerization and the substitute of acetyl group. Then CA fibers were prepared by dry-jet wet spinning process. The tenacity and the E-modulus of the regenerated CA fibers were up to 3.0 cN/dtex and 75 cN/dtex respectively, and the former was larger than that of industrial CA fibers prepared by dry spinning process. This is related to the structure of the CA fibers, because the crystallinity, crystal orientation of the fibers can be improved by high draw ratio during dry-jet wet spinning process. Otherwise, the CA fibers showed no fibrillation tendency, which showed improved wearing comfort compared to lyocell fibers. This work provided an effective way to produce new CA fibers with higher tensile strength.

AQUEOUS N -METHYLMORPHOLINE N -OXIDE AS A NEW MEDIUM FOR ALKYLATION OF PYRAZOLES

It is shown that alkylation of pyrazoles with (E)/(Z)-1,3-dichlorobut-2-enes can be carried out in an alkaline aqueous medium in the presence of N-methylmorpholine N-oxide. In some cases, this technique may substitute phase-transfer catalysis. Conformational analysis of the reaction products showed that a mixture of (E)/(Z) isomers is formed in a ratio of 9:1.

Hydrogen‐Bonding Interactions in the Ley–Griffith Oxidation: Practical Considerations for the Synthetic Chemist

The Ley–Griffith oxidation, which is catalyzed by tetra‐n‐propylammonium perruthenate (TPAP, nPr4N[RuO4]), is a popular method for not only controlled oxidation of primary alcohols to aldehydes, but also a host of other synthetically useful transformations. While the fundamental reaction mechanism has recently been elucidated, several key hydrogen‐bonding interactions between the reagents were implicated but not investigated. Herein the prevalence of H‐bonding between the co‐oxidant N‐methylmorpholine N‐oxide (NMO), the alcohol substrate, water and the perruthenate catalyst is established. These observations help to rationalize the importance of drying the reagents and lead to several practical suggestions.