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Moritz Ehrenstein Pawel Sikorski Edward Atkins Paul Smith 《Journal of Polymer Science.Polymer Physics》2002,40(23):2685-2692
Structural studies and morphological features of a new family of linear, aliphatic even–even, X 34‐nylons, with X = 2, 4, 6, 8, 10, and 12, are investigated with X‐ray diffraction and electron microscopy. Solution‐grown crystals were obtained by isothermal crystallization from N,N‐dimethylformamide solutions. The thickness of lamellar‐like crystals was orders of magnitude less than the chain lengths of the polymer samples used, implying that the chains fold to form chain‐folded lamellae. The results bear a close resemblance, with the noticeable exception of 2 34‐nylon, to those reported for nylon 6 6 and other even–even nylon chain‐folded lamellar crystals. The basic structure of the straight‐stem lamellar core is similar to that of the classic nylon 6 6 triclinic α structure, and the chains tilt ≈42° relative to the lamellar normal. In the case of 2 34‐nylon, the structure resembles the 2 Y nylon series, and the chain tilt angle reduces to 36.6°. These combined results suggest that, even with a relatively low frequency of amide units along the backbone of these molecules, hydrogen bonding is still the dominant element in controlling the behavior, structure, and properties of these polymers. In addition, gels were prepared in concentrated sulfuric acid, and gel‐spun fibers were studied using X‐ray diffraction. The data are interpreted in terms of a modified nylon triclinic α structure that bears a resemblance to the structure of even–even nylons at elevated temperatures. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2685–2692, 2002 相似文献
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The syntheses of the antimony analogue of betaine, Me3Sb+CH2COO? (1), of the precursor [Me3SbCH2COOH][Br] (2) and of [Me3SbCH2COOCH2CH3][Br] (3) are reported. A new method for the synthesis of solvent‐free Me3Sb is described. The structures of 1·H2O and 3 were determined by single crystal X‐ray diffractometry. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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Michael I. Bruce Julianne Davy Ben C. Hall Yvonne Jansen van Galen Brian W. Skelton Allan H. White 《应用有机金属化学》2002,16(10):559-568
Several trans‐platinum(II) complexes, of the type R′? {Pt(PBu3)2}? R″? {Pt(PR3)2}? R′, where R′ and R″ are groups derived from a series of aromatic alkynes and diynes, have been prepared and characterized. Extensive spectroscopic data for these and other known related complexes are presented. A more precise structural study of trans‐Pt(C≡CC6H4C≡CPh)2(PBu3)2 (cf. Z. Kristallogr. 1998; 213: 483) is reported. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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Solid solution phases Li7‐2xMgx[VN4] (0 < x ≤ 1) with varying Mg‐content are obtained as yellow microcrystalline powders from heat treatment of mixtures of VN, Li3N and Mg3N2 or from mixtures of Li7[VN4] and Mg3N2 at 1370 K in N2 atmosphere at ambient pressure. At substitution parameter values of x > 0.5 a subsequent distortion from the ideal cubic unit cell to an orthorhombic unit cell is observed. The crystal structure of Li7‐2xMgx[VN4] with x ≈ 1 was refined from neutron and X‐ray powder diffraction data (space group Pbca, No. 61, a = 963.03(3) pm, b = 958.44(3) pm, c = 951.93(2) pm, neutron pattern 14° — 156° 2θ, step non‐linear ≈ 0.0782° 2θ, No. of measured points 1816, Rp = 0.089, Rwp = 0.115, RBragg = 0.155, RF = 0.114; X‐ray pattern 10° — 98° 2θ, step 0.005° 2θ, No. of measured points 17600, Rp = 0.028, Rwp = 0.045, RBragg = 0.113, RF = 0.133, structure variables: 45). The crystal structure resembles a Li2O type superstructure with the atomic arrangement of β‐Li7[VN4] and with two crystallographic Li‐sites each substituted by Mg with statistical occupation factors of 0.5. Chemical analyses prove the composition and XAS spectroscopy at the V K‐edge support the +5 oxidation state assignment for vanadium. XAS data also support the tetrahedral coordination of vanadium by N as indicated by the structure refinements. 相似文献
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Dr. Thomas J. Demars Dr. Mrinal K. Bera Dr. Soenke Seifert Dr. Mark R. Antonio Dr. Ross J. Ellis 《Angewandte Chemie (International ed. in English)》2015,54(26):7534-7538
Ceric ammonium nitrate (CAN) is a single‐electron‐transfer reagent with unparalleled utility in organic synthesis, and has emerged as a vital feedstock in diverse chemical industries. Most applications use CAN in solution where it is assigned a monomeric [CeIV(NO3)6]2? structure; an assumption traced to half‐century old studies. Using synchrotron X‐rays and Raman spectroscopy we challenge this tradition, converging instead on an oxo‐bridged dinuclear complex, even in strong nitric acid. Thus, one equivalent of CAN is recast as a two‐electron‐transfer reagent and a redox‐activated superbase, raising questions regarding the origins of its reactivity with organic molecules and giving new fundamental insight into the stability of polynuclear complexes of tetravalent ions. 相似文献
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Syntheses and Crystal Structures of tBu‐substituted Disiloxanes tBu2SiX‐O‐SiYtBu2 (X = Y = OH, Br; X = OH, Y = H) and of the Adducts tBu3SiOH·(HO3SCF3)0.5·H2O and tBu3SiOLi·(LiO3SCF3)2·(H2O)2 The disiloxanes tBu2SiX‐O‐SiYtBu2 (X = Y = H, OH) are accessible from the reaction of CF3SO2Cl with tBu2SiHOH or tBu2Si(OH)2. By this reaction the disiloxane tBu2SiH‐O‐SiHtBu2 is formed together with tBu2SiH‐O‐SiOHtBu2. The disiloxanes tBu2SiX‐O‐SiYtBu2 (X = Y = Cl, Br) can be synthesized almost quantitatively from tBu2SiH‐O‐SiHtBu2 with Cl2 and Br2 in CH2Cl2. The structures of the disiloxanes tBu2SiX‐O‐SiYtBu2 (X = H, Y = OH; X = Y = OH, Br) show almost linear Si‐O‐Si units with short Si‐O bonds. Single crystals of the adducts tBu3SiOH·(HO3SCF3)0.5·H2O and tBu3SiOLi·(LiO3SCF3)2·(H2O)2 have been obtained from the reaction of tBu3SiOH with CF3SO3H and of tBu3SiO3SCF3 with LiOH. According to the result of the X‐ray structural analysis (hexagonal, P‐62c), tBu3SiOLi · (LiO3SCF3)2·(H2O)2 features the ion pair [(tBu3SiOLi)2(LiO3SCF3)3(H2O)3Li]+ [CF3SO3]?. The central framework of the cation forms a trigonal Li6 prism. 相似文献
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Chloro(trifluorophosphane)gold(I): [Au(PF3)Cl] X‐ray quality crystals of [Au(PF3)Cl] (orthorhombic, Pnma) are obtained from a toluene / pentane solution at 6 °C. According to the result of the X‐ray structural analysis, [Au(PF3)Cl] contains an almost linear F3P‐Au‐Cl unit. The shortest Au‐Au contacts between two of these units are 3.3495(9) Å. 相似文献
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《合成通讯》2013,43(15):2067-2077
Abstract We have synthesized and characterized a series of alkyl and aryl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amines through a high‐yield, three‐step procedure starting from 4‐methylquinolin‐2‐ol. Nitration using concentrated nitric/sulfuric acids, followed by chlorination in phosphorus oxychloride, yielded 2‐chloro‐4‐methyl‐6‐nitro‐quinoline. All of the intermediates and aminated products have been characterized by multinuclear (1H and 13C) NMR spectroscopy, elemental analysis, and, in the case of the two title compounds (ethyl and cyclohexyl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amine), a single crystal X‐ray structure was obtained to verify the nature of the new materials. 相似文献
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Paul V. Bernhardt Dr. Geoffrey A. Lawrance Brian W. Skelton Allan H. White 《无机化学与普通化学杂志》2007,633(7):1036-1039
Cations derived by protonation of the ligand title compound (L1) have been structurally characterized in their di‐ and tetra‐ protonated forms in the salts [H2L1][ClO4]2·2H2O and [H4L1][ZnCl4]2·4H2O. In both structures, one half of the formula unit comprises the asymmetric unit of the structure, the macrocycle being centrosymmetric, with the two macrocycles adopting similar conformations. In both salts, a pair of diagonally opposed macrocyclic secondary amine groups are protonated; in the [H4L1]4+ salt, the additional pair of protons are accommodated on the exocyclic pendant amine groups. The dispositions of the pendent amines differ between the two structures, being ‘equatorial’ with respect to the macrocyclic ring in the [H2L1]2+ salt, and ‘axial’ in the [H4L1]4+ salt. In other structurally characterized compounds containing [H4L1]4+ the equatorial disposition was found in the ferricyanide adduct, while in the tetraperchlorate salt the axial disposition was identified. The differences in disposition of the exocyclic groups are ascribed to the extensive H‐bonding in the lattices. 相似文献
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X‐ray standing wave (XSW) field generated under Bragg reflection condition in a periodic Mo/Si multilayer structure has been used to determine the concentration and location of various trace element contaminants embedded in different layers of that multilayer structure. We have used intense synchrotron X rays for XSW analysis. It is observed that various trace element impurities such as Cr, Fe, Ni and W get embedded unintentionally in the multilayer structure during the deposition process. Consequences of such impurity incorporation on the optical properties of the multilayer structure are discussed in hard and soft X‐ray regions. Present measurements are important in order to optimize the deposition methods on one hand and to better correlate the measured optical properties of a multilayer structure with theoretical models on the other. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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The antimony analogue of choline bromide, [Me3SbCH2CH2OH]Br ( 1 ), is formed by the reaction of Me3Sb with BrCH2CH2OH. Crystals of (Me3SbCH2COO)8(NaBr)7(MeOH)9(H2O) ( 2 ) are obtained from [Me3SbCH2COOH]Br and Na2CO3 in methanol. Crystals of 1 contain stibonium cations with intramolecular coordination of the ethanolic group. The structure of 2 features supramolecular units where the carboxylic groups of stiba betaine molecules are in bridging positions between sodium ions. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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The chemoselective reaction of hydrazine on the ketone rather than the ester in a gem diester system with a γ‐keto group by hydrazinium sulfate and a tandem deesterification of one of the esters in this system by N,N‐dimethylformamide are reported. 相似文献
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The reaction of Te(OH)6 with Ph3SnOH in ethanol leads to the formation of trans‐[(Ph3SnO)4Te(OH)2] ( 1 ). Compound 1 crystallizes triclinic in the space group Pbar{1} with a = 996.6(2) pm, b = 1365.4(3) pm, c = 1368.2(3) pm and α = 71.15(2)°, β = 71.48(2)°, γ = 74.81(3)° (at 220 K). The molecular structure of 1 consists of a tellurium atom, which is coordinated nearly octahedrally by four Ph3SnO units and two hydroxyl groups that are trans to each other. The Te–O bond lengths are in the range of 190.5(2) and 193.7(2) pm. Treatment of 1 with methanol under reflux yields trans‐[(Ph3SnO)2Te(OMe)4] ( 2 ). Compound 2 crystallizes triclinic in the space group Pbar{1} with a = 1012.8(1) pm, b = 1422.4(2) pm, c = 1618.1(2) pm, and α = 100.44(1)°, β = 107.92(1)°, γ = 110.66(1)° (at 220 K). 2 forms centrosymmetric molecules in which the tellurium atom is surrounded nearly octahedrally by four methoxy groups and two trans arranged Ph3SnO units. The Te–O bond lengths of 187.9(3)–194.5(3) pm are similar to those observed in 1 . 相似文献
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Basic structural data of two sequential poly(ester amide)s derived from glycolic acid, 1,6‐hexanediamine, and adipic acid or dodecanodioic acid have been determined by means of X‐ray and electron diffraction patterns from fibers and single crystals. Chain‐folded lamellar crystals were obtained by isothermal crystallization from diol or glycerine solutions, and the crystalline habit was investigated by real space electron microscopy. Polyethylene decoration techniques were applied to evaluate the regularity of the folding surfaces. Spherulites prepared from evaporation of formic acid solutions were also studied. The two sequential poly(ester amide)s crystallized according to triclinic and monoclinic unit cells, in which the a crystallographic parameter was close to the typical distance between hydrogen‐bonded chains. Projections viewed down the chain axis revealed differences in the packing mode since oblique and rectangular cells were found for the adipic acid and dodecanodioic acid derivatives, respectively. Both structures can be envisaged as a stacking of hydrogen‐bonded sheets although clear differences concerning the shift between consecutive sheets and the number of layers comprising the unit cell were found. The large unit cells that have been deduced seem to be a consequence of the different packing preferences of the diester and diamide moieties. Both polymers have a molecular conformation that deviates from the all‐trans conformation typical of aliphatic polyamides and polyesters with a large number of methylene groups. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 194–206, 2009 相似文献
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Reaction of Ti(OCH2CH2OR)4 (R?CH3 and C2H5) with 8‐hydroxyquinoline in benzene at room temperature resulted in the formation of Ti(C9H6NO)2(OCH2CH2OR)2, characterized by IR, 1H‐NMR, UV and mass spectroscopies. The molecular structure of Ti(C9H6NO)2(OCH2CH2OCH3)2 has been determined by single‐crystal X‐ray structure analysis. The geometry at titanium is a distorted octahedron, with the nitrogen atoms of quinolinate occupying the trans position with respect to oxygens of the 2‐methoxyethoxy groups. The prepared quinolinate derivatives of titanium alkoxides are very stable towards hydrolysis and harsh conditions are required for hydrolytic cleavage. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献