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991.
M. J. Whitcombe A. Gilbert G. R. Mitchell 《Journal of polymer science. Part A, Polymer chemistry》1992,30(8):1681-1691
The syntheses of three methacrylate monomers with cinnamate ester side-chains and of a further monomer with a corresponding cinnamide side-chain are described. Two of the monomers, with isomeric structures, were thermotropic liquid crystals. Although the clearing points were very similar the crystal melting points differed by 8°C. One compound also exhibited a monotropic smectic phase, behavior not shown by its isomer. The other two monomers were not liquid crystalline. The monomers were polymerized by free radical polymerization, both as homopolymers and as copolymers with methyl methacrylate. In the case of one of the mesogenic ester monomers, copolymers with a cyanophenyl benzoate monomer were also prepared. Three of the four monomers formed thermotropic liquid crystalline homopolymers and the copolymers with the benzoate monomer were also liquid crystalline. The monomers were considered as photoactive components of polymeric liquid crystals. As a preliminary investigation of their photochemistry, copolymers with methyl methacrylate were prepared and irradiated in solution with a broad-band source. Under these conditions two of the materials show a facile photo-Fries rearrangement of the aryl cinnamate ester group. © 1992 John Wiley & Sons, Inc. 相似文献
992.
Preparation, Raman Spectra, and Crystal Structures of V2O3(SO4)2, K[VO(SO4)2], and NH4[VO(SO4)2] The oxo-sulfato-vanadates(V) V2O3(SO4)2, K[VO(SO4)2], and NH4[VO(SO4)2] have been prepared as crystals suitable for X-ray structure determination. In all structures sulfate acts as an unidentate ligand only toward a single vanadium atom. The structure of V2O3(SO4)2 consists of a threedimensional network of pairs of cornershared VO6 octahedra with one terminal oxygen atom each, and SO4 tetrahedra. All oxygen atoms of the sulfate ions are coordinated. NH4[VO(SO4)2] and K[VO(SO4)2] are isostructural. VO6 octahedra with one terminal oxygen atom and pairs of sulfate tetrahedra form infinite chains by corner sharing. The chains are weakly interlinked to layers. The sulfate ions are distorted towards planar SO3 molecules and single oxygen atoms attached to vanadium. This structural detail gives an explanation for the mechanism of the reversible reaction K[VO(SO4)2] ? K[VO2(SO4)] + SO3 at 400°C. Raman spectra of the compounds have been recorded and interpreted with respect to their structures. Crystal data: V2O3(SO4)2, monoclinic, space group P21/a, a = 947.2(4), b = 891.3(3), c? 989.1(4) pm, β = 104.56(3)°, Z = 4, 878 unique data, R(Rw) = 0.039(0,033); K[VO(SO4)2], orthorhombic, space group P212121, a = 495.3(2), b = 869.6(9), c = 1 627(1)pm, Z = 4, 642 unique data, R(Rw) = 0,11(0,10); NH4[VO(SO4)2], orthorhombic, space group P212121, a = 495.3(1), b = 870.0(2), c = 1 676.7(4)pm, Z = 4, 768 unique data, R(Rw) = 0.088(0.083). 相似文献
993.
On the Crystal Structure of Ba2ZnO3 Single crystals of Ba2ZnO3 were prepared by solid state reaction. It crystallizes monoclinic: space group C ? C12/c1; a = 5.833; b = 11.376; c = 12.585 Å; β = 93.63°; Z = 8. The crystal structure is characterised by [ZnO3] chains along [100]. They are connected by Ba2+ in seven fold oxygen coordination. 相似文献
994.
On the Reaction of Macrocycles with Lanthanoids. I. The Crystal Structure of [Li(thf)][(C22H22N4)2Ce] · THF In THF CeBr3 forms with [(TMTAA)Li2] the paramagnetic doubledecker complex [Li(thf)][(TMTAA)2Ce]. The complex crystallizes with 1 Mol THF per formula unit. The structure was characterized by X-ray single crystal structure analysis (space group C2 (No. 5), z = 6, a = 1741.8(2) pm, b = 1622.1(2) pm, c = 2540.4(3) pm, β = 104.72(1)°). The sandwich-like arrangement of the heterocyclic ligands leads to a quadratic-prismatic coordination of the Ce3+ ion. One macrocyclic ligand is additionally coordinated by a [Li(thf)]+ fragment. The coordination of the Li ion is square pyramidal. 相似文献
995.
A new molybdenum(V) diphosphate KMoP2O8 has been isolated. The single crystal X-ray diffraction study of this phase has shown that it is isotypic with KNbP2O8. It crystallizes in the P21/n space group a = 5.0862(4), b = 11.720(1), c = 11.486(1) Å, β = 90.91(1)°. The structure of this phase is compared with those of other molybdenum(V) diphosphates. This tunnel structure is described in terms of [MP2O8]8∞ ribbons running along ā, showing close relationships with the titanophosphate NaTiP2O7. The existence of one free apex for each MoO6 octahedron and each P2O7 group, respectively, is emphasized, allowing a great flexibility of the structure. 相似文献
996.
3-Diethylamino-5-phenyl-1,2,4-diselenazolium-tetrachloroniccolate(II) — Synthesis and Structure Bis-(N′, N′-diethyl-N-benzoylselenoureato)nickel(II) reacts with diphosgene in benzene to 3-diethylamino-5-phenyl-1,2,4-diselenazolium-tetrachloroniccolate(II). Its structure is confirmed by RKSA and ESCA. The compound consists of cations, which are planar fivemembered rings and of tetrahedral tetrachloroniccolate(II) anions. The complex is isomorphic with 3-diethylamino-5-phenyl-1,2,4-dithiazolium-tetrachloroniccolate(II). 相似文献
997.
Pt电极上吸附原子对仲丁醇电催化氧化性能的影响 总被引:1,自引:0,他引:1
运用电化学循环伏安和石英晶体微天平研究了HClO4溶液中仲丁醇在Pt电极及以Sb和S吸附原子修饰的Pt(Pt/Sbad和Pt/Sad)电极上的电催化氧化过程 .从电极表面质量变化可以看出 ,仲丁醇的氧化与电极表面的氧物种有着极其密切的关系 .Pt电极表面Sb吸附原子可在较低的电位下吸附氧 ,明显提高仲丁醇的氧化活性 .与Pt电极相比 ,Sb吸附原子修饰的Pt电极使仲丁醇氧化的峰电位负移约 10 0mV .相反 ,Pt电极表面S吸附原子的氧化会消耗表面氧物种 ,抑制仲丁醇的氧化 .从电极表面质量变化提供了吸附原子电催化作用的数据 相似文献
998.
Bredikhin A. A. Lazarev S. N. Bredikhina Z. A. Savel"ev D. V. Vandyukova I. I. Gubaidullin A. T. Litvinov I. A. 《Russian Chemical Bulletin》2003,52(4):846-852
Crystalline specimens of homochiral and racemic glycidyl p-toluenesulfonate were studied by IR spectroscopy, differential scanning calorimetry, and X-ray diffraction analysis. The melting phase diagram of glycidyl p-toluenesulfonate was constructed. The stacking effect in the crystals of the racemic sulfonate is responsible for a more dense molecular packing, with the result that a heterochiral type of crystallization becomes more favorable. 相似文献
999.
Zyuzin I. N. Golovina N. I. Fedorov B. S. Shilov G. V. Nechiporenko G. N. 《Russian Chemical Bulletin》2003,52(3):761-763
Alkylation of potassium salt of methylnitrosohydroxylamine with 1,7-dichloro-2,4,6-triaza-2,4,6-trinitroheptane afforded 2,3,6,8,10,13,14-heptaaza-6,8,10-trinitro-4,12-dioxapentadeca-2,13-diene 2,14-dioxide. The structure of the reaction product was established by X-ray diffraction analysis. 相似文献
1000.
Alan P Marchand Bishwajit GangulyCarolina I Malagón Huiguo LaiWilliam H Watson 《Tetrahedron》2003,59(10):1763-1771
Diels-Alder cyclodimerization of 1,2,3,4,5-pentachlorocyclopentadiene (1) affords 2a as the exclusive reaction product. Diels-Alder cycloaddition of 1 to norbornadiene also proceeds stereoselectively to produce a single [4+2] cycloadduct, 4c. The structures of 2a and 4c were established unequivocally via application of single crystal X-ray crystallographic techniques. The origins of the observed diastereofacial selectivity in each of these cycloaddition processes have been investigated by application of semiempirical (AM1 Hamiltonian) and ab initio (Hartree-Fock 3-21G*) calculations. The computational results thereby obtained, which are based upon consideration of the kinetically favored transition state for each of the two cycloaddition reactions studied, are consistent with experiment. These semiempirical and ab initio methods also have been used to investigate the mechanisms of the Diels-Alder reactions that have been used to prepare aldrin and isodrin (7 and 8, respectively). The results thereby obtained suggest that isodrin formation via Diels-Alder cycloaddition of cyclopentadiene to 1,2,3,4,7,7-hexachloronorbornadiene proceeds with kinetic control of product stereochemistry. 相似文献