Phase-equilibrium and cellulose-coagulation kinetics for cellulose solutions in <Emphasis Type="Italic">N</Emphasis>-methylmorpholine-<Emphasis Type="Italic">N</Emphasis>-oxide

The dissolution of cellulose in N-methylmorpholine-N-oxide monohydrate and the dissolution of N-methylmorpholine-N-oxide monohydrate in water have been studied via optical interferometry. A part of the phase diagram for the cellulose/N-methylmorpholine-N-oxide system has been constructed. The phase diagram is characterized by crystalline equilibrium, hysteresis of the melting temperatures of the solvents, and a region of anisotropy. Optical interferometry has been used for the first time to study the kinetics of cellulose coagulation during the interaction of cellulose solutions in N-methylmorpholine-N-oxide with water and water solutions of N-methylmorpholine-N-oxide. Information on the values of interdiffusion coefficients and the morphologies of the resulting cellulose films has been obtained. The possibility to use optical interferometry to analyze the interaction of a solution with the coagulating agent in the case of cellulose fiber and film formation has been demonstrated. The influences of temperature, the nature of the coagulating agent, and the cellulose content on the kinetics of the process and morphologies of the formed films have been shown. The use of N-methylmorpholine-N-oxide as a part of the coagulation system decreases the rate of interdiffusion of solutions, thereby resulting in a more uniform and dense morphology of cellulose films. Increased temperature causes diffusion acceleration, thereby leading to the formation of an anisotropic morphology of the cellulose films.     

Solutions of mixtures of cellulose and synthetic polymers in <Emphasis Type="Italic">N</Emphasis>-methylmorpholine-<Emphasis Type="Italic">N</Emphasis>-oxide

Phase state and morphological features of solutions of cellulose blends with rigid-chain thermotropic LC copolyesters and isotropic poly(m-phenyleneisophthalamide) in the highly polar donor solvent N-methylmorpholine-N-oxide are studied by DSC and polarization microscopy. The ternary phase diagram for the cellulose-copolyesters-N-methylmorpholine-N-oxide system is constructed. Rheological characteristics of the prepared solutions are studied using capillary and rotary rheometers under the regimes of continuous and periodic shear deformation. Rheological characteristics of cellulose solutions with copolyesters in N-methylmorpholine-N-oxide with their different phase states are shown to change in accordance with the traditional mechanism of flow for solutions with high specific interactions between their components. However, the character of the rheological behavior of mixtures of cellulose with poly(m-phenyleneisophthalamide) in N-methylmorpholine-N-oxide primarily stems from structural-morphological transformations in solutions taking place upon deformation.     

Discoloration of cellulose solutions in <Emphasis Type="Italic">N</Emphasis>-methylmorpholine-<Emphasis Type="Italic">N</Emphasis>-oxide (Lyocell). Part 2: Isolation and identification of chromophores

The Lyocell process is a modern green industrial fiber-making technology, which employs N-methylmorpholine-N-oxide monohydrate (NMMO) to directly dissolve cellulose. One problem in Lyocell processing is the discoloration of the spinning dope due to chemical side reactions. Two different methods were elaborated to isolate chromophores, which are present in minute amounts only, from Lyocell fibers, the first one using hydrogen chloride in alcoholic solution, the second one employing boron trifluoride – acetic acid complex. Several chromophores were unambiguously identified by a combination of analytical techniques and comparison to authentic samples. Carbohydrate condensation products, such as catechols, were shown to dominate in early phases of chromophore formation. In later stages, these initial chromophores undergo further condensation reactions with degradation products of NMMO and NMMO itself, leading to nitrogen-containing heterocycles and quinoid products, among others. The incorporation of nitrogen into the chromophores and thus the participation of the solvent in chromophore formation were proven.     

Copolymer of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diallyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylammonium chloride with maleic acid as drug carrier

A copolymer of N,N-diallyl-N,N-dimethylammonium chloride with maleic acid of constant composition was prepared under the conditions of radical initiation. The possibility of the functionalization of the copolymer with drugs containing amino groups by polymer-analogous transformations was examined. Conditions were found for preparing conjugates of the copolymer with isoniazid. The structures and the quantitative compositions of the conjugates were determined by ¹³С NMR spectroscopy, and the possibility of preparing conjugates with controlled drug content was demonstrated.     

Molecular properties of the copolymers of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diallyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylammonium chloride and maleic acid

The hydrodynamic and conformational properties of molecules of poly(N,N-diallyl-N,N-dimethylammonium chloride) and N,N-diallyl-N,N-dimethylammonium chloride-maleic acid copolymers of different compositions in solutions with various ionic-strength and pH values, as well as of the polyelectrolyte complex based on the copolymer with dodecyl sulfate anions in chloroform, are studied. For poly(N,N-diallyl-N,N-dimethylammonium chloride) molecules in a 1 M NaCl solution, the Kuhn segment length and the hydrodynamic diameter of the chain are estimated as A = 3.9 nm and d = 0.48 nm, respectively. In acidic solutions with pH 3.5, the copolymers demonstrate behavior typical for polyelectrolytes. In an alkaline solution with pH 13, when 1 M NaCl is added to the solution of the copolymer containing 29 mol % maleic acid units, there is an antipolyelectrolyte effect that manifests itself as an increase in the intrinsic viscosity of the copolymer and in the hydrodynamic radius of its molecules. It is found that an increase in the fraction of maleic acid units in the copolymer from 12 to 42 mol % brings about a reduction in the equilibrium rigidity of its macromolecules from 4.1 to 2.2 nm. The equilibrium rigidity of polyelectrolyte-complex molecules is higher than that of initial copolymer molecules owing to steric interactions arising between the aliphatic chains of dodecyl sulfate anions. In an electric field, the molecules of the complex are oriented owing to the induced dipole moment resulting from the displacement of dodecyl sulfate anions along the chain contour.     

Morphology of polysaccharide blend fibers shaped from NaOH, <Emphasis Type="Italic">N</Emphasis>-methylmorpholine-<Emphasis Type="Italic">N</Emphasis>-oxide and 1-ethyl-3-methylimidazolium acetate

The aim of this study was to find newly structured biopolymer blends bearing those adjustable features able to produce innovative materials. Apart from cellulose derivatives (cellulose carbamate and carboxymethyl cellulose), mannans (guar gum, locust bean gum, and tragacanth gum), xylan, starch (cationized), ι-carrageenan, and xanthan were chosen as blend polysaccharides for cellulose as matrix. In order to study their integration into the cellulose skeleton, fibers were shaped from three different solvents: NaOH by a special wet-spinning process, as well as N-methylmorpholine-N-oxide (NMMO) and 1-ethyl-3-methylimidazolium acetate (EMIMac) via Lyocell technology. The structure and morphologies of the fibers were analyzed by X-ray wide-angle scattering and atomic force microscopy. Hydrophilic/hydrophobic properties were determined by means of a contact angle, as well as moisture content and water retention values, while the surface properties throughout zeta-potential measurements. Being very different processes, the wet spinning in NaOH solution and the dry–wet spinning are deeply impacted by the types of solvent and polysaccharide. The X-ray results for NMMO fibers revealed the highest orientation compared with EMIMac having the lowest orientation of NaOH fibrous types. AFM images also show the lowest surface roughnesses for NMMO and EMIMac fibers. The moisture content and water retention values support these trends, while the water contact angle results show insignificant differences between the samples from EMIMac and NaOH, even though the values calculated for NMMO fibers were the lowest.     

A cautionary note on thermal runaway reactions in mixtures of 1-alkyl-3-methylimidazolium ionic liquids and <Emphasis Type="Italic">N</Emphasis>-methylmorpholine-<Emphasis Type="Italic">N</Emphasis>-oxide

N-Methylmorpholine-N-oxide (NMMO) cannot be completely separated by extraction from mixtures with common 1,3-dialkylimidazolium ionic liquids (ILs) due to strong ionic interactions between the two components. At elevated temperatures, above approx. 90 °C, especially under dry conditions and in the presence of acid, alkylating or acylating agents, remaining NMMO in ILs tends to undergo autocatalytic degradation. This is a highly exothermic, unstoppable process that results in explosions, flames, and complete charring of the reaction mixtures. Thus, caution must be exercised when drying or heating ILs that were in previous contact with NMMO, and the absence of amine oxide must be confirmed to avoid potential danger.     

<Emphasis Type="Italic">Z</Emphasis>-and <Emphasis Type="Italic">E</Emphasis>-conformers of <Emphasis Type="Italic">N</Emphasis>-chloroacetylcytisine

N-Chloroacetylcytisine was synthesized by acylation of (–)-cytisine. Stable Z- and E-conformers with respect to rotational isomerism around the N-12–CO bond were found in PMR spectra at room temperature. The point at which PMR resonances of the Z- and E-conformers coalesced upon heating was measured. The transition barrier between the conformers was estimated.     

Thiocyanation of <Emphasis Type="Italic">N</Emphasis>-arylsulfonyl-, <Emphasis Type="Italic">N</Emphasis>-aroyl-, and <Emphasis Type="Italic">N</Emphasis>-[(<Emphasis Type="Italic">N</Emphasis>-arylsulfonyl)benzimidoyl]-1,4-benzoquinone imines

Reactions of thiocyanate ion with N-aroyl-, N-arylsulfonyl-, and N-(N-arylsulfonylbenzimidoyl)-1,4-benzoquinone imines follow the 1,4-addition pattern, and the adducts undergo intramolecular cyclization to give the corresponding N-substituted 5-amino-1,3-benzoxathiol-2-ones as final products.     

Synthesis of amino acid conjugates of glycyrrhizic acid using <Emphasis Type="Italic">N</Emphasis>-hydroxyphthalimide and <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>'-dicyclohexylcarbodiimide

Synthesis of amino acid conjugates of glycyrrhizic acid with the use of N-hydroxyphthalimide, N,N'-dicyclohexylcarbodiimide, and tert-butyl esters of L-amino acids (valine, isoleucine, phenylalanine, and methionine) was performed followed by deprotection with trifluoroacetic acid. The target amino acid conjugates were isolated by column chromatography on silica gel in 40–45% yield. The structure of the prepared compounds was confirmed by IR and ¹³C NMR spectroscopy.     

Reactions of 1-nitrocyclohexene with <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-binucleophiles

A modification of 1-nitrocyclohexene synthesis is proposed; its reaction with phenylhydrazine and benzoic acid hydrazide is shown to afford monoadducts, and with hydrazine hydrate, bisaduct. With diphenylguanidine occurs heterocyclization to 1-phenyl-2-N-phenylamino-4,5,6,7-tetrahydrobenzimidazole, whose structure is confirmed by the X-ray diffraction data. The analysis performed for this compound of the electron density distribution function in the crystal made it possible to estimate the charge distribution, π-electrons delocalization nature, and the role of N-H…N, C-H…H-C and C-H…C interactions in the formation of the crystal packing.     

Reactions of <Emphasis Type="Italic">N</Emphasis>-Allyl- and <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Diallyltrifluoromethanesulfonamides with Carboxylic Acid Amides under Oxidizing Conditions

Reactions of acetamide and benzamide with N-allyltrifluoromethanesulfonamide in the presence of t-BuOCl–NaI afforded exclusively 2,5-bis(chloromethyl)-1,4-bis(trifluoromethanesulfonyl)piperazine. Analogous reaction with N,N-diallyltrifluoromethanesulfonamide gave mixed halogenation product at only one C=C double bond of the substrate.     

<Emphasis Type="Italic">N</Emphasis>-halohexamethyldisilazanes

The review is devoted to N-halohexamethyldisilazanes, perspective but scantily studied halogenating agents. Methods of preparation, physiochemical characteristics, and synthetic potential are considered. Mechanisms of a number of reactions are presented.     

Equilibrium Compositions of HF Solutions in <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Dimethylformamide

For HF solutions in DMF, concentration-dependent fractions of DMF molecules (α(DMF)) that remain unassociated and that enter heteroassociates (HAs) of 1 : 1, 4 : 1, and 12 : 1 molecular stoichiometries were obtained by two independent methods, namely, from an analysis of IR spectra and by calculating the material balance. The experimental way was shown to be enough exact in determining the ratio between the solvent molecules in four different states up to ~83 mol % HF. The equilibrium compositions of HF–DMF solutions were estimated over the entire range of concentrations. Starting with [HF] of ~25 mol %, more than one-half HF molecules are associated, and at [HF] of ~50–92 mol %, at least 90% of the HF molecules are associated. The equilibrium composition of HF–organic solvent (Solv) solutions in which HAs of 1 : 1, 1 : 4, and 1 : 12 molecular stoichiometries are formed, can be described by a single set of α(HF–Solv) versus concentration plots.     

<Emphasis Type="Italic">N</Emphasis>-allyl and <Emphasis Type="Italic">N</Emphasis>-propargyl trifluoromethanesulfonimides. Theoretical analysis

Tautomers of N-allyl- and N-propargyl-substituted trifluoromethanesulfonimides (CF₃SO₂)₂NR (R = CH₂CH=CH₂, Z/E-CH=CHMe, CH₂C≡CH, CH=CH=CH₂, C≡CCH₂) were calculated by the DFT (B3LYP, wB97XD, PBE1PBE), MP2, and CBS-QB3 methods. The results were compared with the theoretical data for the corresponding amines and amides NHRR¹ (R¹ = H, CF₃SO₂). It was shown that there is no conjugation between the nitrogen atom and C=C bond and that conjugation exists with the C≡C bond with electron density displacement toward the nitrogen atom. The calculations of anions derived from N-allyl- and N-propargyl-trifluoromethanesulfonimides revealed the possibility of their rearrangement with elimination of trifluoromethanesulfinate anion and formation of its H-complex with N-(prop-2-en-1-ylidene)trifluoromethanesulfonamide or N-(prop-2-yn-1-ylidene)trifluoromethanesulfonamide.     

Pathways of decomposition of <Emphasis Type="Italic">N</Emphasis>-cyclopropyl <Emphasis Type="Italic">N</Emphasis> nitrosoureas in methanol

Decomposition of a series of N-cyclopropyl-N-nitrosoureas (CNU) in CD₃OD was studied. These decompose much more rapidly than N-methyl-N-nitrosourea, one of the decomposition pathways being denitrosation, which is atypical of alkylnitrosoureas under the reaction conditions used. The nature of substituents in the cyclopropane ring has a great effect on the stability of CNU and the product ratio. In the presence of H₂ SO₄, decomposition occurs much more rapidly. Possible pathways of the formation of the major decomposition products of CNU are proposed based on the experimental data.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 359–370, February, 2005.     

Conformations and properties of <Emphasis Type="Italic">O</Emphasis>-Alkyl-<Emphasis Type="Italic">S</Emphasis>-(2-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dialkylamino)-ethylmethylthiophosphonates

Conformers of the biologically active compounds CH₃P(O)(OR)(SCH₂CH₂NR ₂ ^′ ), where (I) R = i-C₄H₉, R′ = C₂H₅ and (II) R = C₂H₅, R′ = i-C₃H₇, are calculated within the AM1 level of theory. The elongated and twisted forms with maximum and minimum distances between a nitrogen atom and those of a phosphorus tetrahedron, respectively, and bearing a syn and anti oriented alkoxy group relative to a phosphoryl oxygen, are studied. It is found that the differences between the energy, electronic, and geometric parameters of these forms are apparent in differences between their properties, e.g., the ability to participate in complexation and protonation, reactions that to some extent simulate the interaction between a substance and a biological object.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-and <Emphasis Type="Italic">C</Emphasis>-trimethylsilyl-substituded anililes

N-Metallation of bromoanilines with ethylmagnesium bromide followed by a reaction with trimethylchlorosilane provided N-mono and N-bis(trimethylsilyl)bromoanilines depending on the structure of substrate. The metallation of bissilylated bromoanilines with butyllithium permitted the introduction of a trimethylsilyl substituent in the aromatic ring. Previously unknown 2-bromo-N,N-bis(trimethylsilyl)aniline, 2,6-dibromo-N-trimethylsilylaniline, 2,6-dibromo-N,N-bis(trimethylsilyl)aniline, 2-bromo-6-trimethylsilylaniline, 2-bromo-6-trimethylsilyl-N,N-bis(trimethylsilyl)aniline, 2-bromo-6-trimethylsilyl-N-trimethylsilylaniline, 2,4,6-tribromo-N-trimethylsilylaniline, and 2,4,6-tribromo-N,N-bis(trimethylsilyl)aniline were prepared. The structures of the compounds obtained were established by the chromato-mass spectrometry and ¹H, ¹³C, and ²⁹Si NMR spectroscopy.