Chemical structure and surface properties of the polyurethane cationomers

Polyurethane cationomers were synthesised in the reaction of various diisocyanates with polyoxypropylene glycol and two N-alkyldiethanolamines. The obtained isocyanate prepolymers were then extended in the aqueous medium by means of 1,6-hexamethylenediamine; stable aqueous dispersions were thus obtained, which were applied to and distributed over the poly(tetrafluoroethylene) surface. After evaporation of water from those dispersions, thin polymer coatings were produced. The analyses with the use of ¹H, carbon-13 nuclear magnetic resonance and infrared spectroscopy methods confirmed chemical structures of synthesised cationomers. Also, attempts were made to quantitatively characterise polarities of those structures by means of factors that were defined especially for that purpose. Moreover, the physical model of van Oss–Good and wetting angles for coatings obtained from the polyurethane cationomers in question, measured with the use of standard liquids with various polarity specifications, were utilised to determine the surface free energy values for the obtained ionomers.     

Novel Synthesis,Characterization of N1,N1,N4,N4-tetrakis (2-hydroxyethyl) terephthalamide (THETA) and Terephthalic Acid (TPA) by Depolymerization of PET Bottle Waste Using Diethanolamine

Chemical depolymerization of poly(ethylene terephthalate) (PET) waste is a possible remedy to huge amount of solid waste generation as it results in degradation products that possess a potential of recyclability. PET bottle waste was depolymerized by aminolysis using diethanolamine. Novel synthesis of N¹, N¹,N⁴,N⁴-tetrakis (2-hydroxyethyl) terephthalamide (THETA) with 73-76% yield and terephthalic acid (TPA) with 78-82% yield was achieved. The purified products were analyzed by FTIR, melting point, DSC, DTG and ¹H-NMR. THETA has various applications in the synthesis of rigid polyurethane foam, unsaturated polyester resins and also as a cross linking agent/ hardener for epoxy resins.     

N-Oxides of polychloropyridines.13C NMR study

The effect ofN-oxidation of a series of polychloropyridines on¹³C NMR parameters has been studied. It has been established that inN-oxides of polychloropyridines an electric field through-space effect of theN-oxide group predominates in the shielding of the -carbon atom compared to the other carbon atoms. A linear correlation between¹³C NMR chemical shifts and total charge densities calculated by the MNDO method for the carbon atoms ofN-oxides of polychloropyridines has been found.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2425–2428, December, 1995.The authors are grateful to V. V. Kolchanov for help in the synthesis of compounds under study.     

An Easy Preparation of Chemically Pure,High-Activity Tritium-Labelled N-Propionylampicillin for the Analysis of Penicillin-Binding Proteins

Abstract

The laboratory preparation of chemically pure, ³H-labelled β-propionylampicillin suitable for studies of the mode of action of β-lactam antibiotics has been investigated. The chemical purity of the labelled antibiotic is a crucial factor for the quantitative determination of penicillin-binding proteins. Ampicillin (D-α-aminobenzylpenicillin) was N-[³H]propionylated by N-succinimidyl [³H]propionate, the labelled reaction products were analyzed by thin-layer chromatography followed by fluorography. The synthesis and the purification of the resulting N-[³H]propionylampicillin have been optimized, the best conditions for the acylation reaction were at pH 8.25 for 2 h, giving both a high yield of the labelled antibiotic and minimal amounts of unwanted by-products. The reaction mixture was fractionated by a two-step procedure, the purified radioactive antibiotic did not contain any residual reactant, especially free ampicillin, or degradation products such as D-α.-[³H]propionamidobenzylpenicilloic acid. This improved procedure allows an easy, fast and rather inexpensive preparation of a good quality radiolabeled antibiotic for studies of penicillin-interacting proteins.     

Mercury(II) cyanide complexes with alkyldiamines: solid-state/solution NMR,computational, and antimicrobial studies

Mercury cyanide complexes of alkyldiamines (1–6), [Hg(L)(CN)₂] (where L?=?en (1,2-diaminoethane), pn (1,3-diaminopropane), N-Me-en, N, N′-Me₂-en, N, N′-Et₂-en, and N, N′-ipr₂-en), have been synthesized and characterized by elemental analysis, IR, ¹³C, and ¹⁵N solution NMR in DMSO-d₆, as well as ¹³C, ¹⁵N, and ¹⁹⁹Hg solid-state NMR spectroscopy. Complexes 1 and 2 have been studied computationally, built and optimized by GAUSSIAN03 using DFT at B3LYP level with LanL2DZ basis set. Binding modes of en and bn (where bn?=?1,4-diaminobutane) toward Hg(CN)₂ are completely different. Complexes with en and pn show chelating binding to Hg(II), while bn behaves as a bridging ligand to form a polymeric structure, [Hg(CN)₂-bn]_∞ [B.A. Al-Maythalony, M. Fettouhi, M.I.M. Wazeer, A.A. Isab. Inorg. Chem. Commun., 12, 540 (2009).]. The solution ¹³C NMR of the complexes demonstrates a slight shift of the ?C≡N (0.9 to 2?ppm) and ?C–NH₂ (0.25 to 6?ppm) carbon resonances, while the other resonances are relatively unaffected. ¹⁵N labeling studies have shown involvement of alkyldiamine ligands in coordination to the metal. The principal components of the ¹³C, ¹⁵N, and ¹⁹⁹Hg shielding tensors have been determined from solid-state NMR data. Antimicrobial activity studies show that the complexes exhibit higher antibacterial activities toward various microorganisms than Hg(CN)₂.     

DMA水溶液的1H NMR研究

测量了N,N-二甲基乙酰胺(DMA)水溶液体系不同温度下全浓度范围的¹H NMR数据, 对体系中的缔合情况进行了讨论, 应用化学缔合模型求得了各缔合平衡常数K和缔合平衡的ΔH. 结合N,N-二甲基甲酰胺(DMF)和N-甲基乙酰胺(NMA)水溶液的研究结果, 发现酰胺自身结构和酰胺浓度是影响酰胺水溶液性质的主要因素.     

Formation of ionic liquid submicron particles. 1H and 19F nuclear magnetic resonance spectroscopic studies

We prepared novel ionic liquid submicron particles (ILSPs) in water by emulsifying the ionic liquid (IL) N-(2-methoxyethyl)-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr_12O1TFSI), which is immiscible with water, with the nonionic surfactants Tween 20 and Span 80. The mean particle size and zeta potential of the ILSPs were about 580?nm and ?30?mV, respectively. The ILSPs were characterized using ¹H and ¹⁹F nuclear magnetic resonance (NMR) spectroscopic methods. The chemical shifts of the Pyr_12O1⁺ cation and TFSI^? anion in the ¹H and ¹⁹F NMR spectra of the ILSP suspension were consistent with those corresponding to pure Pyr_12O1TFSI. This indicated that most of the Pyr_12O1TFSI was still in the IL state in the ILSP suspension. In addition, ¹H–¹H nuclear Overhauser effect correlated spectroscopic measurements showed that the ILSP droplets contained Pyr_12O1TFSI in the neat IL steric state even in the ILSP suspension, and Pyr_12O1TFSI species localized in the droplet surfaces interacted with the hydrophobic acyl side chains of the surfactants. These NMR spectroscopic results show that the ILSPs formed an IL-in-water microemulsion in which droplets of neat Pyr_12O1TFSI were surrounded by the two surfactants, that is, Tween 20 and Span 80.     

Interaction of cellulose with amine oxide solvents

Cellulose I, mainly as ramie or as Avicel microcrystalline cellulose, has been monitored by optical microscopy and by ¹³C CPMAS NMR, over the course of its dissolution in hot N-methylmorpholine N-oxide solvent. Its interaction with the near-solvent N-ethylmorpholine N-oxide and related non-solvents has also been investigated. NMR shows that N-methylmorpholine N-oxide partly converts crystalline cellulose I into amorphous solid cellulose. The changes in chemical shift imply increased flexibility at the glycosidic bonds. In contrast, N-ethylmorpholine N-oxide converts cellulose I to cellulose III_I, without dissolution. Microscopy shows that the ramie fibres swell laterally, and at least some also shorten longitudinally, during dissolution. Model studies using methyl--d-glucopyranose show no evidence from ¹³C chemical shifts for different modes of binding with different solvents. However, N-methylmorpholine N-oxide binds more strongly to methyl--d-glucopyranose in DMSO than does N-ethylmorpholine N-oxide, whereas N-ethylmorpholine N-oxide binds better to H₂O. Also, ¹³C T ₁ values for aqueous cellobioside show increasing rotational freedom of the –CH₂OH sidechains as N-methylmorpholine N-oxide is added. Together, these observations imply the initial penetration of solvents and near-solvents between the molecular cellulose sheets. Subsequently, N-methylmorpholine N-oxide breaks H-bonds, particularly to O-6, just sufficiently to loosen individual chains and then dissolve the sheets.     

Stereochemical studies, 73. Saturated heterocycles, 60

N-Substituted-2-carboxamido-1-cycloalkanols were cyclized with 1,1-carbonyldiimidazole to synthesizecis- andtrans-N-alkyl-,N-aralkyl- andN-aryl-2,4-dioxo tri- and tetramethyleneperhydro-1,3-oxazines. The structures of the compounds and theircis ortrans ring anellation were confirmed by IR,¹H- and¹³C-NMR spectroscopy, and thecis andtrans pairs of isomers were compared to establish the predominant conformation of the flexiblecis isomers. It was found that—similarly to the 1,3-oxazin-2- and -4-ones studied earlier—the O-endo conformers are preferred, in which the 1-oxygen atom isaxial to the alicyclic ring; this is independent of the number of ring atoms in the alicycle, and of the presence of an oxazinedione ring, even though this is more flexible that the ring of oxazinones.

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Synthese und Konformation voncis undtrans 2-substituierten kondensierten 1,3-Oxazin-2,4-dionen

Zusammenfassung cis- undtrans-N-Alkyl-,N-Aralkyl- undN-Aryl-2,4-dioxo-, tri- und tetramethylen-perhydro-1,3-oxazine wurden aus 2-Carboxamido-1-cycloalkanolen und 1,1-Carbonyldiimidazol dargestellt. Mit Hilfe der IR,¹H- und¹³C-NMR Spektroskopie wurden die Struktur, diecis- odertrans-Annellierung der Ringe und die bevorzugte Konformation der flexiblencis-Isomeren im Vergleich zumcis-trans Isomerenpaar nachgewiesen. Ähnlich zu den früher untersuchten 1,3-Oxazine-2- und -4-onen ist hier ebenfalls das O-endo Konformere bevorzugt; in diesem ist der Sauerstoffaxial angeordnet, und zwar unabhängig von der Zahl der alicyklischen Ringatome und dem flexibleren Oxazindionring.

     

Mechanism of thermal degradation of polyurethanes investigated by direct pyrolysis in the mass spectrometer

Direct pyrolysis in the mass spectrometer (MS) yielded unequivocal evidence regarding the mechanism of thermal decomposition of N-monosubstituted and N-disubstituted polyurethanes. It was ascertained that direct pyrolysis in the MS detects the primary thermal fragments that originate from polyurethane pyrolysis. This is particularly useful when, as in the thermal decomposition illustrated in eq. (1), it is necessary to distinguish between primary and secondary thermal fragments in order to assess the thermal degradation mechanism. Our results indicate that N-monosubstituted polyurethane V undergoes a quantitative depolycondensation process. Instead, the thermal decomposition of the N-disubstituted polyurethane VI which occurs selectively in eq. (1) is demonstrated by the detection of thermal fragments that contain secondary amine and olefinic end groups. Finally, polyurethane VI shows a higher thermal stability with respect to polymer V because of the absence of the depolycondensation process, which accounts for the thermal degradation of the N-monosubstituted polyurethane V.     

Synthesis and characterisation of coating polyurethane cationomers containing quaternary ammonium alkyl groups derived from built-in alkyl bromides

Polyurethane cationomers were synthesised in the reaction of 4,4′-methylenebis(phenyl isocyanate) with polyoxypropylene glycol (M = 450) and N-methyl diethanolamine. Amine segments were built-in to the urethane–isocyanate prepolymer in the reaction with 1-bromoalkanes (C₂–C₁₀), and then they were converted to alkyl-ammonium cations. The obtained isocyanate prepolymers were then extended in the aqueous medium. That yielded stable aqueous dispersions which were applied on the surfaces of test poly(tetrafluoroethylene) plates. After evaporation of water, the dispersions formed thin polymer coatings. ¹H and ¹³C NMR spectral methods were employed to confirm chemical structures of synthesised cationomers. Based on ¹H NMR and IR spectra, the factors κ and α₁ or α₁ were calculated, which represented the polarity level of the obtained cationomers. The differential scanning calorimetry method revealed decline of T _g for the hard urethane and urea segments from 60 °C to 46 °C when the number of carbon atoms increased in the alkyl radical attached to the ammonium cation. Changes were discussed in the surface free energy (SFE) and its components, as calculated independently according to the methods suggested by van Oss-Good and by Owens–Wendt, in relation to chemical structures of cationomers. The growing length (from C₂ to C₁₀) of the alkyl radical attached to the N atom in the cationomer chain was found to reduce the value of SFE of the polymer coating from 46 to 28 mJ/m². That is caused by gradual weakening of long-range interactions, within which the highest share is taken by dispersion interactions.     

Tetraalkylammonium Ions in Aqueous and Non-aqueous Solutions

Property data for tetraalkylammonium cations, [H(CH₂) _n ]₄N⁺, are reviewed. They pertain to the isolated cations and their transfer from the gas phase into aqueous solutions. Various properties of these cations in aqueous and non-aqueous solutions and data for their transfer between these are also reviewed. Emphasis is placed on the dependence of data on the length n of the alkyl chains rather than on the absolute values. Most of the data are available only for the first four members of the series. The properties of the isolated ions increase linearly with the chain length. Molar enthalpies of formation of the gaseous and aqueous cations, and absolute standard molar enthalpies of hydration, are derived. Standard molar entropies of dissolution of several salts in water are obtained from their solubilities and enthalpies of solution. The molar entropies of the crystalline iodides of the first four members of the series then give the standard partial molar entropies of the aqueous cations and their molar entropies of hydration. The standard partial molar volumes in aqueous and non-aqueous solutions are quite linear with n and in non-aqueous solutions the molar volume hardly depends on the nature of the solvent. On transfer from water to non-aqueous solvents the volume of Me₄N⁺ suffers some shrinkage, that of Et₄N⁺ appears to be unaffected, but from Pr₄N⁺ onwards an increasing expansion takes place. This unexpected result is tentatively explained by hydrophobic intra-molecular association of pairs of alkyl chains in aqueous solutions, resulting in a tightening of the structure. The transfer of the R₄N⁺ cations from water into non-aqueous solvents is governed by a large positive entropy change, outweighing the smaller positive enthalpy change. The transport properties of the aqueous R₄N⁺ cations are non-linear with n. A major impediment to movement is thus the sticking of the water molecules to the ice-like hydrophobic hydration sheaths of the larger cations. The number of water molecules affected by the hydrophobic cations is open to widely differing estimates resulting from various approaches, and constitute an open issue.     

Quantum Chemical Calculations on the Structure and Adsorption Properties of NO and N2O on Ag+ and Cu+ Ion-Exchanged Zeolites

Ab initio cluster quantum chemical calculations at the Hartree–Fock (HF/Lanl2dz) and correlated second-order Moller–Plesset perturbation theory (MP2/Lanl2dz) levels were performed for NO and N₂O interactions with Ag⁺ and Cu⁺ ion-exchanged zeolites. The interaction energies were estimated in a conventional way and also corrected for basis set superposition errors. It was shown that the highly dispersed Ag⁺ counterions establish twofold coordination to the lattice oxygens on the zeolite surface, similar to the case of Cu⁺ ions. However, both NO and N₂O bind relatively strongly to the Cu active sites of Cu⁺ ion-exchanged zeolites than those of the Ag⁺ site of the Ag⁺ ion-exchanged zeolites. Based on the results of these calculations, the two different forms of adsorption for these molecules on the catalyst surface, the nature of their binding and characteristics of the adsorption properties have been discussed. Finally, some comparisons with the results obtained by a variety of density functional theory calculations on target systems have been presented.     

1-(2′,2′,2′-Trifluoroethyl)-4-phosphopyrazoles: Synthese et Etude Spectroscopique ir et RMN 1H, 13C, 19F,et 31P

Seven new 1-fluorinated-4-phosphopyrazoles 2 have been prepared in 60–94% yield by cyclization of N-(2′,2′,2′-trifluoroethyl) phosphonyl β-hydrazones 1 with triethyl orthoformate in the presence of acetic acid. The IR data, the ¹H, ¹³C, ¹⁹F, ³¹P chemical shifts and coupling constants of the compounds 2 are reported.     

Solid state N and C NMR study of dioxomolybdenum (VI) complexes of Schiff bases derived from trans-1,2-cyclohexanediamine

The ¹³C, ¹⁵N CP MAS NMR and FT-IR spectra of dioxomolybdenum (VI) complexes of trans-N,N′-bis-(R-salicylidene)-1,2-cyclohexanediamine (R=H, R=3,5-diCl, R=3,5-diBr, R=4,6-diOCH₃), trans-N,N′-bis-(2-OH-naphthylidene)-1,2-cyclohexanediamine and trans-N-(salicylidene)-N′-(2-OH-naphthylidene)-1,2-cyclohexanediamine have been measured. Comparative analysis of the NMR and IR spectra of the complexes with those of the corresponding ligands has shown that the complexation of the di-Schiff bases leads to changes in the conformation of the ligands and the charge redistribution. The asymmetric structure and non-planar structure of the complexes have been suggested.     

CHEMISTRY OF CIS- AND TRANS-9-PHENYLSELENOXANTHENE-N-ARYLSULFONYLSELENILIMINES1

Abstract

cis- and trans-9-Phenylselenoxanthene-N-(arylsulfonyl)selenilimines were synthesized and isolated. Their stereochemistry was ascertained from the NMR spectra. Cis isomers reacted with chloramine-T or -B by an S_N 2 type substitution to form trans isomers, but the reverse reaction did not take place. When trans isomers were refluxed in toluene they underwent intermolecular 1,4 rearrangement to give 9-arylsulfonamido-9-phenylselenoxanthene. The cis isomers neither rearranged nor isomerized. On treatment with DABCO, both isomers rearranged intermolecularly to 9-(N-arylsulfonamido)selenoxanthenes at room temperature. Hydrolysis of both isomers yielded trans-9-phenylselenoxanthene 10-oxide. Reactions with p-methoxyphenylmagnesium bromide or methylmagnesium iodide afforded 9-(p-methoxyphenyl)-9-phenylselenoxanthene or 9-phenylselenoxanthene as a main product, respectively.     

Regioselectivity of fluorine substitution by alkoxides on unsymmetrical difluoroarenes

An efficient approach to unsymmetrical halogenated resorcinol diethers has been developed. This synthesis consists of two subsequent nucleophilic aromatic substitutions (S_NAr) of unsymmetrical difluoroarenes by alkoxides. The novelty of this approach is its control of regioselectivity during the first S_NAr, which occurs at room temperature. Interestingly, the reactivity of competing fluorines was correlated to their chemical shift in ¹⁹F NMR.     

Configurational and conformational preferences in stereoselective acylations of <Emphasis Type="Italic">N</Emphasis>-methyl-1,3-diaminopropane with acyl chlorides

Evidence for a stereoinduction profile of the reaction of N-methyl-1,3-diaminopropane with acyl chlorides has been provided. A possibility to engage in intramolecular CH₂⋯HN and Cl⋯H-N interactions and the proton migration process to the methylamino group leads to the E secondary amides carrying the N⋯H⁺⋯N or N-H⋯N bridges, that show unusual spectroscopic images. Empirical relations between the Δδ _C chemical shift differences, the polarizability of the CO(S) groups and hydrogen bonding strength have been found. Both ¹H-¹⁵N-GHSQC and GHMBC experiments provide insight into the nature of hydrogen bonding and confirm the cyclic array of atoms.     

CO LMR spectrum of14N16O and its analysis with spectra of14N17O and14N18O

LMR spectra for v=1←0 transitions of¹⁴N¹⁶O in X²II_{1/2, 3/2} states were observed at 5.6 μm and 5.4 μm of CO laser. Introducing the advanced isotopic molecular constant scaling function to Hund’s case (a) diatomic structure model, these spectra were analyzed and fitted together with all reliable previous spectral data of¹⁴N¹⁶O as well as¹⁴N¹⁷O and¹⁴N¹⁸O. A full set of precise molecular parameters and their vibrational dependencies have been determined with much higher precision (1–2 orders for most parameters). Many of them have been obtained for the first time. Using isotopic scaling function, the molecular constants of¹⁴N¹⁷O and¹⁴N¹⁸O were deduced.     

Synthesis, properties, and hepatic metabolism of strongly fluorescent fluorodipyrrinones

From non-fluorescent 8-H fluorophenyldipyrrinones, highly fluorescent (?_F 0.4-0.6) analogs have been synthesized by reaction with 1,1′-carbonyldiimidazole to bridge the dipyrrinone nitrogens and form an N,N′-carbonyldipyrrinone (3H,5H-dipyrrolo[1,2-c:2′,1′-f]pyrimidine-3,5-dione). Amphiphilic, water-soluble 8-sulfonic acid derivatives are then obtained by reaction with concd H₂SO₄. The resulting fluorinated and sulfonated N,N′-carbonyl-bridged dipyrrinones, isolated as their sodium salts, are potential cholephilic fluorescence and ¹⁹F MRI imaging agents for use in probing liver and biliary metabolism. After intravenous injection in the rat they were excreted rapidly and largely unchanged in bile. ¹⁹F NMR spectroscopy of a pentafluorophenyl-tosylpyrrolinone synthetic precursor exhibited rarely seen diastereotopicity.