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.     

<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.     

Synthesis and structure of <Emphasis Type="Italic">N</Emphasis>-(diaminomethylidene)- and <Emphasis Type="Italic">N</Emphasis>-[bis(cyclohexylamino)methylidene]trifluoromethanesulfonamides

N-Trifluoromethylsulfonyl-substituted guanidines CF₃SO₂N=C(NHR)₂ (R = H, cyclohexyl) were synthesized in nearly quantitative yield by reactions of N-sulfinyltrifluoromethanesulfonamide CF₃SO₂N=S=O with urea and of trifluoromethanesulfonamide with N,N′-dicyclohexylcarbodiimide. N-[Bis(cyclohexylamino)-methylidene]trifluoromethanesulfonamide was subjected to protonation with trifluoromethanesulfonic acid and bis(trifluoromethanesulfonyl)imide, and the structure of the resulting salts and initial N-trifluoromethylsulfonylguanidines was studied by NMR and IR spectroscopy and DFT quantum-chemical calculations.     

Halogenophilic and classical <Emphasis Type="Italic">Ad</Emphasis><Subscript><Emphasis Type="Italic">N</Emphasis></Subscript><Emphasis Type="Italic">E</Emphasis> mechanisms in nucleophilic vinylic substitution reactions involving the anions of transition metal carbonyls

The mechanism of the reaction of carbonylate anions ([M(CO) _n L]^–) with highly activated vinyl halides (Hal = Cl, Br, I) was investigated by the method of “anion traps” – the effect of proton donors on the composition of the reaction products. It was demonstrated that the reactions with PhCHal=C(Z)₂ (Hal = Br, I;Z=CN, CO₂Et) and PhCN=CClI take place through initial attack by the carbonylate at the halogen atom, the reactions with PhCCl=C(CO₂Et)₂ and PhCOCH=CHHal (Hal = Cl, I) take place through attack by the carbonylate at the π bond (Ad_NE mechanism), and in the case of E-and Z-PhCN=CHI the two mechanisms operate concurrently. The main laws determining the reaction mechanisms are analyzed.     

Determination of epoxides by high-performance liquid chromatography following derivatization with <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diethyldithiocarbamate

A reversed-phase, high-performance liquid chromatography (RP-HPLC) method that allows quantitation of low levels of epoxides has been described. The method involved derivatization of epoxides using 100- to 1,000-fold excess N,N-diethyldithiocarbamate (DTC) at 60 °C for 20 min at neutral pH. The unreacted DTC was then decomposed to CS₂ and diethyl amine by acidification of the reaction mixture to pH 2 using orthophosphoric acid. The first two steps could be performed in the same reaction vessel by sequential addition of reagents. In the final step, an aliquot (20 μL) of the derivatized sample was analyzed for the presence of stable esters of DTC by RP-HPLC using a Supelcosil LC-18-S (150 × 4.6-mm) column and a mobile phase consisting of 40% (v/v) acetonitrile in water at a flow of 1 mL min⁻¹. Using UV detection at 278 nm, the epoxides gave linear responses in the concentration range of 0.25 to 50 μM. The method is robust, and as low as 5 pmol of the analyte could be successfully detected and quantified with recoveries of ≥94%. Following a minimal pretreatment such as ultrafiltration (molecular weight cutoff 5,000 Da), the method is suitable for analysis of epoxides in complex physiological fluids (e.g., fetal bovine serum). The method has been rigorously evaluated and adapted in our laboratory for routine analysis and determination of stability of epoxides of 1,3-butadiene and other alkenes added to cell cultures.     

The application of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylhydroxylamine as reductant for the separation of plutonium from uranium

Both single stage and multi-stages experiments on stripping plutonium with N,N-dimethylhydroxylamine (DMHAN) as reductant with methylhydrozine (MMH) as supporting reductant were carried out. The effect of contact time, temperature, acidity, concentration of DMHAN on back-extraction rate of plutonium was investigated in the single stage experiment. The results demonstrated that the reaction of stripping Pu(IV) in the organic phase (30% TBP–kerosene) 1BF solutions by DMHAN exhibits excellent stripping efficiency. Under the given conditions, the back-extraction rate of plutonium reaches 90% within 2 min. Higher temperature, lower acidity and the increased concentration of DMHAN benifit the stripping reaction. The concentration profile of HNO₃, uranium and plutonium were determined in a multi-stages mixer-settler after the steady state of the back-extraction, and the multi-stages results show that the plutonium can be separated effectively from uranium. The recovery of plutonium and uranium reach 99.995% or over 99.99% respectively. The separation factor of U from Pu (SF_Pu/U) is about 2 × 10⁴.     

Thermodynamic characteristics of the complexation between Pb<Superscript>2+</Superscript> and <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Bis(carboxymethyl)aspartic acid in aqueous solution

The enthalpies of complexation between N,N-bis(carboxymethyl)aspartic acid (H₄Y) and the Pb²⁺ ion at 298.15 K were determined from calorimetric data for a wide range of the ionic strengths (KNO₃). The thermodynamic characteristics ΔH, ΔG, and ΔS, of formation of the complexes PbHY⁻ and PbY²⁻ were calculated for zero and fixed ionic strengths. The results obtained were interpreted.     

<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.     

Synthesis and structure of Pt(II) acetamidate complexes containing <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethyl-substituted ethylenediamine and trimethylenediamine

Reactions of acetamide with platinum(II) diamines [Pt(N,N-DimeEn)Cl₂], [Pt(Tm)Cl₂], and [Pt(N,N-DimeTm)Cl₂] (N,N-DimeEn = (CH₃)₂N(CH₂)₂NH₂, Tm = NH₂(CH₂)₃NH₂, N,N-DimeTm = (CH₃)₂N(CH₂)₃NH₂) with preliminary precipitation of chlorine ions by silver salts gave binuclear Pt(II) acetamidates [Pt₂(CH₃)₂N(CH₂)₂NH₂)₂(μ-NHCOCH₃)₂](NO₃)₂ · H₂O (I), [Pt₂(NH₂(CH₂)₃NH₂)₂)(μ-NHCOCH₃)₂](NO₃)₂ · H₂O (II), and [Pt₂(CH₃)₂N(CH₂)₃NH₂)₂(μ-NHCOCH₃)₂](HSO₄)₂ (III), whose crystal structures were determined. Crystals of I are monoclinic: a = 14.459(2) Å, b = 17.197(3) Å, c = 9.822(2) Å, β = 105.923(10)°, V = 3348.6(8) ų, space group P2(1)/c, Z = 4, R _hkl = 0.0419 for 6663 reflections. Complex I is a binuclear acetamidate with bridging (NHCOCH₃)^? ligands, one of which is bound to two Pt atoms through the N and O atoms, and the other ligand is bound only through the N atom. The Pt-Pt distance is 2.987(1) Å. Crystals of II are monoclinic: a = 10.213(7) Å, b = 13.373(9) Å, c = 16.533(11) Å, β = 97.971(9)°, V = 2236(3) ų, space group P2(1)/n, Z = 4, R _hkl = 0.557 for 6462 reflections. The Pt-Pt distance is 3.057(1) Å. Crystals of III are monoclinic: a = 10.557(12) Å, b = 18.531(2) Å, c = 14.4744(17) Å, β = 108.705(2)°, V = 2682(5) ų, space group P2(1)/n, Z = 4, R _hkl = 0.569 for 8506 reflections. The Pt-Pt distance is 3.202(1) Å. Complexes II and III are binuclear acetamidates, in which two chelating Pt(Tm) or Pt(N,N-DimeTm) moieties are coordinated through the N and O atoms of (NHCOCH₃)^? cis-bridges.     

Reactions of <Emphasis Type="Italic">N</Emphasis>-aroxycarbonyltrichloroacetimidates with nucleophilic phosphorus derivatives

Aryl N-aroxycarbonyltrichloroacetimidates (Ar = Ph, 4-FC₆H₄) react with diphenylphosphinite according to the scheme of the aza-Perkow reaction to give the corresponding aryl N-(1-aroxy-2,2-dichloro-vinyl)-N-diphenylphosphinoylcarbamates. The structure of one of these compounds was confirmed by single crystal X-ray diffraction analysis. In the case of electron-accepting substituents (Ar = 4-O₂N₆H₄), the primary product undergoes mild -elimination to give nitrophenyl diphenylphosphinate and 1-nitrophenoxy-2,2-dichlorovinyl isocyanate. The reaction of trichloroacetimidates with triethyl phosphite yields a mixture of O- and N-phosphorylation products.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 11, 2004, pp. 1797–1803.Original Russian Text Copyright © 2004 by Rassukanaya, Onysko, Sinitsa, Bolbut, Chernega.This revised version was published online in April 2005 with a corrected cover date.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-(2-chloroethyl)glycine and -<Emphasis Type="SmallCaps">DL</Emphasis>-alanine esters

Two methods for the synthesis of N-(2-chloroethyl)glycine and-DL-alanine esters are proposed: 1) reductive amination of the C=O group of glyoxilic or pyruvic acids upon treatment with 2-chloroethylamine and sodium cyanoborohydride in methanol and 2) alkylation of 2-chloroethylamine with α-haloalkanoic acid esters in K₂CO₃-MeCN two-phase system. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2372–2374, December, 2007.     

Synthesis and properties of <Emphasis Type="Italic">N</Emphasis>-nitro-<Emphasis Type="Italic">O</Emphasis>-(4-nitrophenyl)hydroxylamine

Salts of N-nitro-O-(4-nitrophenyl)hydroxylamine were synthesized by a new method of oxidative nitration, involving the reaction of O-(4-nitrophenyl)hydroxylamine with KNO₂ or NaNO₂ in the presence of PhI(OAc)₂ or PhIO as oxidants. When using Na¹⁵NO₂, the samples containing the nitro group labeled with the ¹⁵N isotope were obtained. Acidification of the appropriate salt gave N-nitro-O-(4-nitrophenyl)hydroxylamine. It is the first N-nitrohydroxylamine isolated in the H-form. Its thermal stability was investigated and the probable mechanism of decomposition was suggested. From a comparison of the ¹⁴N and ¹⁵N NMR spectra of N-nitro-O-(4-nitrophenyl)hydroxylamine with those of its O- and N-methylated derivatives, its equilibrium with the aci-form (N=NOOH) was inferred.     

Hydrogen bonding interactions between <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylformamide and cysteine: DFT studies of structures,properties, and topologies

The hydrogen bonding interactions between cysteine and N,N-dimethylformamide (DMF) were studied at the extended hybrid functional DFT-X3LYP/6-311++G(d,p) level regarding their geometries, energies, vibrational frequencies, and topological features of the electron density. The quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses were employed to elucidate the interaction characteristics in the complexes. The results show that two intermolecular hydrogen bonds (H-bonds) are formed in one complex except few complexes with one intermolecular H-bond. The H-bonds involving O atom of DMF as H-bond acceptor usually are red-shifting H-bonds, while the blue-shifting H-bond usually involve methyl of DMF or methenyl of cysteine moiety as H-bond donors. Both hydrogen bonding interaction and structural deformation play important roles in the relative stabilities of the complexes. Due to the π-bond cooperativity, the strongest H-bond is formed between hydroxyl of cysteine moiety and O atom of DMF, however, the serious deformation counteract the hydrogen bonding interaction to a great extent. The complex involves a stronger hydrogen bonding interaction as well as the smaller deformation is the most stable one. The electron density (ρ_b) as well as its Laplacian (∇²ρ_b) at the H-bond critical point predicted by QTAIM is strongly correlated with the H-bond structural parameter (δR _H···Y) and the second-perturbation energies E(2) in the NBO scheme.     

Mechanochemical synthesis of <Emphasis Type="Italic">N</Emphasis>-triethylborazine

Reactions of ethylamine hydrochloride C₂H₅NH₂HCl with MBH₄ (M = Li, Na, K) under mechanical activation of mixtures of crystalline substances in a vacuum vibratory ball mill are studied. The step-by-step pyrolysis of the reaction products at 90 and 240°C is found to yield N-triethylborazine. The maximum yields of N-triethylborazine are 78.9, 60.3, and 73.8% for LiBH₄, NaBH₄, and KBH₄, respectively. The target product is characterized by various physicochemical methods. The melting point, density, refractive index, and other properties correspond to the literature data for N-triethylborazine.     

Redox Behavior of Neptunium(V) in Tributyl Phosphate and <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Dihexyl Octanamide Extractants Dissolved in <Emphasis Type="Italic">n</Emphasis>-Dodecane

Spectrophotometric investigations have been carried out on the disproportionation of Np(V) to form Np(IV) and Np(VI) in 1.1 mol⋅L⁻¹ solutions of tributyl phosphate (TBP) and in N,N-dihexyl octanamide (DHOA) in n-dodecane medium. The Np(V) was found to coordinate with Np(IV) in 1.1 mol⋅L⁻¹ TBP solution in n-dodecane to form a mixed valence “cation–cation” complex by bonding through an axial oxo group on Np(V). By contrast, this interaction was less prominent in the case of 1.1 mol⋅L⁻¹ DHOA solutions. The effect of 1-octanol, added as phase modifier, on the disproportionation behavior of Np(V) was also investigated. An attempt was made to calculate the disproportionation/reduction rate constants for Np(V) under the conditions of these studies. Absorbance measurements on the Np stripped from organic phases revealed the occurrence of Np(V) in the aqueous phase.     

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.     

Synthesis and properties of <Emphasis Type="Italic">N</Emphasis>-(alkenylidene)trifluoromethanesulfonamides

N-Alkenylidenetrifluoromethanesulfonamides TfN=CH–CR=C(Me)R′ (R, R′ = H, Me) have been synthesized by reaction of N-sulfinyltrifluoromethanesulfonamide TfNSO with (E)-but-2-enal, (E)-2-methylbut- 2-enal, and 3-methylbut-2-enal. Despite greater stability of N-alkenylidenetrifluoromethanesulfonamides relative to their propargyl isomers TfNHCH₂C≡CR, no rearrangement of the latter into the former occurs due to the presence of an acidic NH proton, which hampers formation of carbon-centered anion.     

Homolytic reactions of <Emphasis Type="Italic">N</Emphasis>-bromohexamethyldisilazane with trialkyl(phenylalkoxy) derivatives of silicon and tin

The main product of the photoinduced reaction of N-bromohexamethyldisilazane with trialkyl-(benzyloxy)derivatives of silicon and tin R₃MO(CH₂) _n Ph (R = Me, Et; M = Si, Sn; n = 1) is N,N-dibenzylidene-C-phenylmethanediamine (hydrobenzamide). For M = Si, with increase of the length of the methylene chain between the oxygen atom and the phenyl group (n = 2, 3), the similar reaction affords the product of bromination of the benzylic carbon atom R₃MO(CH₂) _n−1CHBrPh. For M = Sn, the reaction results in the formation of 2-phenyloxacycloalkanes PhCHO(CH₂) _n−1.     

Molecular structure of <Emphasis Type="Italic">N</Emphasis>-(<Emphasis Type="Italic">o</Emphasis>-and <Emphasis Type="Italic">p</Emphasis>-hydroxybenzyl)cytisine

The molecular structures of N-(o-and p-hydroxybenzyl)cytisine were investigated by NMR spectroscopy, x-ray structure analysis, and molecular modeling. It was found that NMR resonances of the OH and aromatic protons in N-(o-hydroxybenzyl)cytisine were doubled because of the presence of two conformers in solution. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 165–168, March–April, 2008.