首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Shi  M. K.  Graff  G. L.  Gross  M. E.  Martin  P. M. 《Plasmas and Polymers》1999,4(4):247-258
Residual gas analysis (RGA) and optical emission spectroscopy have been evaluated as potential in situ techniques for the detection of plasma-induced polymer surface etching. The detection is based on the measurement of CO and CO2 species formed in the gas phase following oxidation of the etching fragments released from the polymer surface. Experiments were performed on poly(ethylene terephthalate) and UV-cured acrylic (tripropylene glycol diacrylate) films exposed to O2 RF (13.56 MHz) plasmas. A linear correlation is obtained between the formation of CO and the polymer etching rate over the entire experimental range, but discrepancies appear for the formation of CO2 at high treatment powers (etching rate > 1.0 g/min.cm2). This behavior is attributed to a deficit of oxidizing agents relative to the generation of etching fragments. The results suggest that both RGA and optical emission spectroscopy can be used to monitor in situ and in real-time the etching of polymer surfaces during plasma treatment.  相似文献   

2.
Solvent effects on the phase separation of poly(-benzyl L-glutamate) to liquid crystal and isotropic solution have been observed in various helicogenic solvents. The temperature-composition phase diagrams have been determined for each solution. The critical concentrations, 2 * , at which the phase separation occours have been compared in various solvents. In dimethylformamide in which the polymer is molecularly dispersed, the observed 2 * value has agreed with that calculated by Flory's theory. In some solvents in which the polymer aggregates in a head-to-tail mode such as chloroform, the observed 2 * values have been considerably small. It is assumed that the polymer aggregates behave as longer particles than the original particles. In dioxane in which the polymer aggregates highly both in a head-to-tail and a side-by-side modes, the 2 * value has been a little larger than that in chloroform. In this case the relationship between the aggregation and the liquid crystal formation is so complicated that further investigation is necessary. In aromatic solvents such asm-cresol that dissolves the polymer almost molecularly, the 2 * is smaller than that in dimethylformamide. Therefore, the intermolecular interactions between the phenyl groups in the side groups of the polymer and those in solvent molecules must be considered.The author is grateful to Mr. K. Sano and Mr. M. Watanabe for their observation of the liquid crystal formation.  相似文献   

3.
Summary 3-Aryl-7-(2-deoxy--D-erythro-pentofuranosyl)-3,7-dihydro-4H-pyrrolo[2,3-d]-pyrimidin-4-imines (4) as well as 4-arylamino-7-(2-deoxy--D-erythro-pentofuranosyl)-2-methyl-5-phenyl-7H-pyrrolo[2,3-d]pyrimidines (7) have been synthesized by glycosylation of the sodium salt of the corresponding nucleobases with 2-deoxy-3,5-di-O-p-toluyl--D-erythro-pentofuranosyl chloride (2) followed by subsequent deprotection with sodium methoxide in methanol. The deprotected nucleoside4 undergoes aDimroth rearrangement on reflux for 24 h in water to furnish the 4-arylamino nucleoside7.
Synthese und Reaktionen von 2-Deoxy--D-ribofuranosylderivaten von 3-Aryl-4H-pyrrolo[2,3-d]pyrimidin-4-iminen
Zusammenfassung 3-Aryl-7-(2-deoxy--D-erythro-pentafuranosyl)-3,7-dihydro-4H-pyrrolo[2,3-d]-pyrimidin-4-imine (4) und 4-Arylamino-7-(2-deoxy--D-erythro-pentofuranosyl)-2-methyl-5-phenyl-7H-pyrrolo[2,3,-d]pyrimidine (7) wurden durch Glycosylierung der Natriumsalze der entsprechenden Nucleosidbasen mit 2-Deoxy-3,5-di-O-p-toluyl--D-erythro-pentofuranosylchlorid (2) und anschließende Entfernung der Schutzgruppe mit Natriummethoxid in Methanol hergestellt. Das entschützte Nucleosid4 ergibt bei 24-stündigem Erhitzen in Wasser unter Rückfluß über eineDimroth-Umlagerung das 4-Aminonucleosid7.
  相似文献   

4.
The kinetics of the nitrosation ofN-methylacetamide have been studied using spectrophotometry. Significant differences with respect to the mechanism of nitrosation of amines were observed: the absence of catalysis by halides, the existence of general basic catalysis by acetate and its chlorated derivatives obeyingBrønsted's law (with =0.49), and the primary isotopic effect (with a ratio of 7.9 between the rate constants for the elementary process in H2O and D2O). All this indicates that the slow step of the mechanism must be the transfer of a proton from the protonated nitrosamide to the reaction medium.
Kinetische Untersuchungen zur Bildung von N-Nitroso-Verbindungen, 10. Mitt.: Die Nitrosierung vonN-Methylacetamid und die Unterschiede in bezug auf die Nitrosierung von Aminen
Zusammenfassung Die Kinetik der Nitrosierung vonN-Methylacetamid wurde mittels Spektrophotometrie untersucht. Es wurden signifikante Unterschiede zum Mechanismus der Nitrosierung von Aminen beobachtet: die Abwesenheit einer Katalyse durch Halogenide, die Existenz einer generellen basischen Katalyse durch Acetat und dessen chlorierten Derivaten unter Übereinstimmung mit demBrønstedschen Gesetz (mit =0,49) und einem beobachtbaren Isotopeneffekt (mit einem Verhältnis von 7,9 zwischen den Geschwindigkeitskonstanten in H2O und D2O). All das zeigt an, daß der geschwindigkeitsbestimmende Schritt im Mechanismus der Transfer eines Protons vom protonierten Nitrosamid zum Reaktionsmedium sein muß.
  相似文献   

5.
The relative stabilities and molecular structures of the geometrical isomers of seven ,-dioxa derivatives of cycloalkylidenecycloalkanes with 3to 6-membered rings have been studied by DFT calculations at the B3LYP/6-31G* level of theory. In each case, the E form was calculated to have the lower total energy. The relative energy of the Z isomer proved to increase regularly with increasing sizes of the two heterocyclic rings, ranging from 1.1 to 13.8 kJ mol–1 on going from the 3,3to the 6,6-membered rings. Intermediate values of the relative energy were calculated for the Z forms of compounds containing two dissimilar rings. The relative energy of the Z isomer was found to be proportional to d –9.3, where d = the distance separating the two O atoms of the Z compound. The molecular structures, electric dipole moments, and atomic charges on the O atoms are also discussed.  相似文献   

6.
Hydrodynamic properties of 10 samples of poly(1-trimethylsilylpropyne) of various molecular weights, obtained with NbCl5 catalyst and containing 60-70% cis C = C bonds, were studied by sedimentation, translation diffusion, and viscometry techniques. The equilibrium rigidity of the polymer molecules was estimated from the viscometric data using the formalism of the intrinsic viscosity theory as applied to the worm-like coil model with excluded-volume effects. For the polymer macromolecules, the Kuhn segment length, thermodynamic parameter , and hydrodynamic diameter of the chain d were estimated.  相似文献   

7.
The cohydrolysis of-cyanoethyl- and-cyanopropylmethyldichlorosilanes with dimethyldichlorosilane has been studied and the optimum conditions ensuring the maximum yield of rings containing cyanoalhyl groups have been determined.B is(-cyanoethyl)hexamethylcyclotetrasiloxane,-cyanopropylpentamethylcyclotetrasiloxane, and bis(-cyanopropyl)hexamethylcyclotetrasiloxane have been obtained for the first time and characterized.  相似文献   

8.
Under electron impact, 6-thiotheophyllines eliminate various fragments from the pyrimidine moiety. In a retro Diels-Alder reaction, they lose the fragment X?C?NCH3 from positions 1 and 2 of the pyrimidine ring. In 6-sulfinyltheophyllines, the sulfinyl group is the main target for fragmentation; it can lose either oxygen or sulfur, and the abundance of [M—16]+ and [M—32]+ is much higher than the abundance of the molecular ion. Elimination of the sulfur atom of the 6-sulfinyl substituent, with retention of its oxygen, may be explained by intermediate formation of a ring. All further fragmentations of the 6-sulfinyl derivatives proceed by a primary loss of oxygen or sulfur, followed by elimination of fragments from the pyrimidine moiety, similar to the primary processes, observed in the mass spectra of the 6-thiotheophyllines.  相似文献   

9.
Four sulfated steroid compounds were isolated from the Kuril population of the starfish Aphelasterias japonica. The structure of a new glycoside, aphelasteroside D, was elucidated as (24R)-29-O-[2-O-sulfo--D-glucopyranosyl]-24-ethyl-5-cholestane-3,5,6,8,15,29-hexol sodium salt. Other three substances were identified as the known pycnopodioside C, 3-O-sulfo-24,25-dihydromarthasterone, and 3-O-sulfothornasterol A, the latter compound being isolated as a tyrammonium salt for the first time.  相似文献   

10.
The title compound 4,8-bis(2-Hydroxybenzyl)-cis-octahydro [1,4]-oxazino [3,2-b]-1,4-oxazine (1) has been synthesized by the reaction of N-(2-hydroxybenzyl)-2-amino-1-ethanol with glyoxal. This novel compound was characterized by elemental analysis, IR, and 1H NMR. The structure was also confirmed by a single crystal X-ray study. The compound crystallizes in monoclinic C2/C space group with unit cell dimensions: a = 18.318(4), b = 8.6110(17), c = 13.267(3) Å, = 119.90(3), V = 1814.1(6) Å3, Z = 4. The two fused six-membered rings in 1 adopt chairlike conformations slightly flattened around the nitrogen atoms. In the central fusion bond, the geometry is a staggered conformation, with the two angular hydrogen atoms in the cis positions with respect to the rings, the nitrogen atoms antiperiplanar to each other, while the oxygen atoms remain gauche to each other and antiperiplanar to the hydrogen atoms. The ring conformations in 1 have been discussed on the basis of the anomeric effects and the presence of two strong intramolecular hydrogen bonds between the phenolic hydrogens and the amino groups.  相似文献   

11.
N,N-DicyclohexylpiperazineN,N-dioxide octahydrate, C16H46N2O10,M r=426.55, monoclinic, space groupC2/m (No. 12),a=12.961(4),b=11.533(4),c=7.907(1) Å, =98.37(2)o,V=1169.3(6) Å3,Z=2. The structure was solved by the direct method and refined toR=0.045 for 1192 observed MoK reflections. TheN,N-dioxide molecule occupies a site of symmetry 2/m. The piperazine ring takes the chair form with the two N–O bonds oriented axially in atrans configuration. Hydrogen bonding between the water molecules, as well as between theN-oxide groups and water molecules, gives rise to a puckered layer composed of edge-sharing four-membered, five-membered, six-membered, and eight-membered rings. Adjacent layers are cross-linked by theN,N-dicyclohexylpiperazine moieties lying between them, thereby generating a sandwich structure consolidated by covalent and hydrogen bonding. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82062 (8 pages).  相似文献   

12.
Tamm  J.  Johanson  U.  Marandi  M.  Tamm  T.  Tamm  L. 《Russian Journal of Electrochemistry》2004,40(3):344-348
Experimental and theoretical methods have been used for characterization of the properties of polypyrrole films. The AFM studies show that the morphology of polypyrrole (PPy) films on polycrystalline gold electrodes at the first stages of synthesis depends on the structure of the metal surface. It was established that mobility of anions depends remarkably on the rate of electrodeposition of the polymer film. If PPy film was deposited at relatively low current density, mobility of ClO- 4 anion was not high enough to guarantee electroneutrality during redox cycling and cations take part in this process especially when Li+ cations were replaced by more mobile + cations. Semiempirical (AM1 and PM3) quantum-chemical methods were used for theoretical studies. It was established that different size and charge of the anions together with the variation in doping levels give rise to a different optimal conformation of oligopyrrole cations which, in turn, define the resulting polymer to be either all-anti (common linear chains) or all-syn (formation of helical structures) or a combination of the two.  相似文献   

13.
    
Continuing investigations in the field of the synthesis of condensed heterocyclic systems containing pyrrole and indole fragments ¦1–3¦, we have condensed of 2-aminopyrrole derivatives with various 1, 3-dicarbonyl compounds. The reaction took place at the boil in solutions in pyridine or acetic acid, and also without a solvent at 150–160° C, forming in a single stage derivatives of pyrrolo[1, 2-a]pyrimidine (I–III) and pyrrolo[2, 1-b]-tetrahydroquinazoline (IV–VI). The condensation of 2-aminopyrrole with acetoacetic and substituted acetoacetic esters led to 4-oxo derivatives of pyrrolo[1, 2-]pyrimidine (VII and VIII).  相似文献   

14.
Four new polyhydroxysteroids, 5-cholesta-3,5,6,15,16,25,26-heptaol, 24-ethyl-5-cholesta-3,5,6,15,28,29-heptaol-29-sulfate, (22E)-24-methyl-5-cholest-22-ene-3,5,6,15,25,26-hexaol-26-sulfate, 24-propyl-5-cholesta-3,5,6,8,15,28,29-heptaol, and the known 5-cholesta-3,5,6,15,16,26-hexaol, have been isolated from the starfishCtenodiscus crispatus.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1821–1825, October, 1994.  相似文献   

15.
Conclusions The synthesis of the heptapeptideN -BOC-N -pelargonyl-L-lysyl-N -Z-L-lysyl-D-phenylalanyl-L-leucyl-N -Z-L-lysyl-N -Z-L-lysyl-L-threonine, a linear analog of the cyclopeptide part of the antibiotic polymixin B, has been effected (yield 63%). The possibility of using this method for the synthesis of peptides on a polymer support without protecting the hydroxyl group of threonine has been shown.Khimiya Prirodnykh Soedinenii, Vol. 6, No. 3, pp. 359–361, 1970  相似文献   

16.
Comparative analysis of the curing performance of epoxy-containing cross-linking agents of different structure in vulcanization of a promising binder for energetic systems, poly-N-methyl-5-vinyltetrazole prepared by the modification procedure and containing residual N–H-unsubstituted tetrazole fragments, was made. Cross-linking of polymer chains of the binder is a result of alkylation of the residual N–H-unsubstituted tetrazole rings in poly-N-methyl-5-vinyltetrazole macromolecules with oxirane rings of the second reactant. Curing of poly-N-methyl-5-vinyltetrazole in the presence of macromolecular curing agents, carbon-chain polymers containing oxirane rings in pendant chains, at temperatures lower than 100°С occurs in a considerably narrower time interval compared to curing with low-molecular-mass epoxy resin.  相似文献   

17.
Isobaric expansibilities P and isothermal compressibilities T have been determined at 25 and 45°C for binary mixtures of ethylbenzene + n-tetradecane and + n-hexadecane and the corresponding excess functions (V E /T)P and (V E /P)T have also been obtained. With these data and supplementary literature values, the following second order mixing properties are also reported at 25°C: S E , (V E /P)T, CV and (VT). All mixing quantities have been compared with the results obtained at 25°C by using the Prigogine-Flory-Patterson theory of liquid mixtures. The predicted values suggest that the ability of ethylbenzene as a breaker of the pure n-Cn orientations is similar to what we found for toluene and higher than for p-xylene.  相似文献   

18.
Conclusions Using Cp2Zr(H)Cl, 1,6-anhydro-2-desoxy-2-C-methyl-3-O-benzyl-4-methylene--D-xylohexapyranose has been reduced with a high degree of stereospecificity to 1,6-anhydro-2,4-didesoxy-2,4-di-C-methyl-3-Obenzyl--D-galactopyranose, which was then converted into the C9-C13 fragments of erythronolide Band oleandonolide.Short communication [1]; previous communication [2].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2568–2572, November, 1982.  相似文献   

19.
The geometry of silatrane HSi(OCH2CH2)3N has been determined by gas electron diffraction, ab initio calculations, and vibrational spectroscopy of crystal. Using the scaled force field from DFT calculations the amplitudes and perpendicular corrections were calculated. It was assumed that the silatrane molecule has C 3 symmetry. The following values (r g bond lengths in Å and a bond angles in deg. with three standard deviations from the least-squared refinements using a diagonal weight matrix) are: SiN 2.406(27); NC 1.443(7); OC 1.399(11); SiO 1.648(3); CC 1.504(15); NSiO 78.8(21); SiOC 128.1(11); SiNC 105.4(14); CCO 117.0(26); CCN 108.2(30); CNC 113.2(17); OSiO 116.3(13). The 5-membered rings are flattened. The sum of its bond angles is equal to 537.5(42). It is shown that a very large difference is found for Si—N distance from ab initio and DFT calculating.  相似文献   

20.
The interactions ofp-tert.-butylcalix[4]arene bearing polyoxyethylene chains (C3) with pyrene (Py), 1-anilino-8-naphthalenesulfonate (ANS) andN-phenyl-naphthylamine (NPN) in aqueous solution were studied by absorption and fluorescence measurements. Absorption spectral changes and fluorescence enhancements reveal that C3, which has a hydrophobic cavity, can include organic molecules and ions in aqueous solution and form 11 host-guest complexes with ANS and NPN. C3 forms inclusion complexes with Py at different stoichiometries depending on the host: guest molar ratio. Binding constants of 2.2×104, 2.0×104 and 3.6×105 dm3 mol–1 were calculated for the C3Py, C3ANS and C3NPN complexes (11), respectively, based on the Benesi-Hildebrand equation.Author for correspondence.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号