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  • kinetics  (77)
  • crystal structure  (60)
  • Springer  (137)
  • American Chemical Society
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  • 2000-2004  (137)
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  • Springer  (137)
  • American Chemical Society
  • American Physical Society
  • Springer Nature
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Synthesis and structure of tetrakis(2,6-dichlorophenoxide) bis(THF) uranium(IV) (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 7-10 
    Details
    ISSN: 1572-8854
    Keywords: crystal structure ; uranium (IV) ; dichlorophenoxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The reaction of UCl4 with KO-2,6-Cl2C6H3 in tetrahydrofuran results in the preparation of the title compound. The six-coordinate complex possesses pseudo-octahedral geometry about uranium, with U-O(phenoxide) bond lengths in the range 2.161(11) to 2.178(10) Å and U-O(THF) bond lengths of 2.467(10) and 2.475(11) Å. This complex crystallizes in the monoclinic space group P21/n (a = 11.169(2), b = 11.588(2), c = 35.119(5) Å, β = 92.11(1)°, V = 4542.2(13) Å3, and Z = 4).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009594612946
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and crystal structure of hexakis(N-methylimidazole) iron(II) pyridine-2-sulfonate (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 23-26 
    Details
    ISSN: 1572-8854
    Keywords: iron ; crystal structure ; synthesis ; N-methylimidazole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The compound [Fe(C4H6N2)6][C5H4NSO3]2 crystallized in the monoclinic space group, P21/n with unit cell parameters: a = 13.676(3), b = 8.345(2), c = 18.663(4) Å, β = 106.40(3)° and Z = 2. The title compound consists of a [Fe(C4H6N2)6]+2 hexacoordinated iron(II) cation and two C5H4NSO− 3 anions. In the cation the iron atom is coordinated to six N-methylimidazole imine nitrogen atoms in a distorted octahedral arrangement. The N1,N5,N1i,N5i atoms are coplanar and the iron lies in this plane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009537830693
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  • 3
    Electronic Resource
    Electronic Resource
    Crystal structure of [Cu2(II)(dmpa)2(p-Cl-C6H5COO)2] (Hdmpa = N,N-dimethyl-3-amino-1-propanol) (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 35-38 
    Details
    ISSN: 1572-8854
    Keywords: copper(II) ; aminoalcoholato ; hydrogen bonding ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The copper complex, [Cu2(II)(dmpa)2(p-Cl-C6H5COO)2], has been prepared and its structure determined using X-ray crystallography. The dimer is a di-μ2-alkoxo complex which is a five-coordinate copper dimer with unsupported alkoxo bridges. The complex crystallizes in the triclinic space group P-1 with a = 11.384(2), b = 14.636(5), c = 9.609(2) Å, α = 100.07(2), β = 104.33(3), γ = 72.79(2)°, V = 1471.8(7) Å3, and Z = 2. The structure is comprised of discrete binuclear clusters in which the metal atoms are bridged by two alkoxo oxygens of the dmpa− ligands. The Cu-O and Cu-N distances are in good agreement with those found for other copper(II) aminoalcoholato complexes. The Cu···Cu distance is 2.9765(6) Å. In the crystal, every two dimeric coordination molecules are combined together by the recognition through intermolecular hydrogen-bonding interactions between the apical water molecule and the non-coordinated O atom from the p-chlorobenzoato ligand, forminga tetramer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009542031602
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis and crystal structure of manganese(III) hydroxyl-containing Schiff base complexes: [Mn(III)(Hvanpa)2]N3 (H2vanpa = 1−(3-hydroxysalicylaldeneamino)-3-hydroxypropane) (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 39-42 
    Details
    ISSN: 1572-8854
    Keywords: manganese(III) ; Schiff base ; hydrogen bonding ; crystal structure ; Jahn-Teller distortion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The manganese complex, [Mn(III)(Hvanpa)2]N3 has been prepared and the crystal structure determined using x-ray crystallography. The mononuclear complex has a six-coordinate octahedral geometry. The complex crystallizes in the monoclinic space group P21/c with a = 9.867(1), b = 13.316(2), c = 9.0110(1) Å, β = 107.870(1)°, V = 1126.8(2) Å3, and Z = 2. The Mn-O and Mn-N distances in the equatorial plane are in good agreement with those found for other manganese(III) Schiff base complexes. In the axial direction, the Mn-O distances of 2.274(2) Å is about 0.3 Å longer than those in the equatorial plane due to a Jahn-Teller distortion at the d4 manganese(III) center. In the crystal, each azido ion is linked through hydrogen bonding with two hydrogen atoms from the coordinate hydroxyl groups at the apical site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009594015672
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  • 5
    Electronic Resource
    Electronic Resource
    Preparation, characterization and crystal structure of an intermolecular compound based on H3PMo12O40·nH2O and diethylamine (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 43-48 
    Details
    ISSN: 1572-8854
    Keywords: molybodophosphoric acid ; crystal structure ; diethylamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An intermolecular compound, H3PMo12O40·5(CH3CH2)2NH·H2O, between the heteropolymolybdate α-H3PMo12O40 and the organic substrate diethylamine, has been synthesized and characterized. Light yellow crystals of the title compound were crystallized from a mixed solvent of water and acetonitrile with formula H3PMo12O40·5(CH3CH2)2NH·H2O. Spectroscopic data support the presence of a sizable electronic interaction between the organic substrate and the inorganic anion in the solid state. The single crystal x-ray structure analysis of the title compound revealed that it crystallized in the triclinic system, space group P $$\overline 1$$ with a = 12.0786(13), b = 12.102(5), c = 21.416(3) Å, α = 94.87(2), β = 94.755(9), γ = 113.81(2)°, V = 2830.3(13) Å3, and Z = 2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009546132511
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis and crystal structure of K3Sb4BO13 (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 53-53 
    Details
    ISSN: 1572-8854
    Keywords: boroantimonate ; borate ; antimonate ; crystal structure ; 49
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract K3Sb4BO13, Mr = 823.11 g.mol−1, crystallizes in the triclinic system, space group P $$\overline 1$$ , Z = 2. The lattice parameters are a = 7.133(1) Å, b = 7.232(1) Å, c = 13.259(2) Å, α = 82.00 (1)°, β = 99.77(1)° and γ = 117.08(1)°, V = 598.7(2) Å3, Dx = 4.566 Mg m−3. The final R index and weighted Rw index are 0.0251 and 0.0623, respectively. The three-dimensional network of the title compound is constituted by layers (Sb3O9)n, similar to that of hexagonal bronze of Magneli. These layers are linked together, in the c direction, alternatively by edge-sharing pairs of SbO6 octahedra and BO3 triangles. This framework has interconnected tunnels, running approximately along the a and b directions, in which the K+ ions are located.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009598116581
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  • 7
    Electronic Resource
    Electronic Resource
    Crystal structure of a (25R)-2α,3α-epoxy-5α-spirostan-6, 23-dione hemi-ethyl acetate solvate (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 693-697 
    Details
    ISSN: 1572-8854
    Keywords: brassinosteroids ; steroids ; natural products ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The compound (25R)-2α,3α-epoxy-5α-spirostan-6,23-dione, crystallizes as a hemi-ethyl acetate solvate, having two host molecules of similar conformation per molecule of ethyl acetate, in the asymmetric unit. The O atom of the epoxy group is α-oriented. The presence of the epoxy group disturbs the chair conformation in the ring A of the steroidal nucleus. Ring A has a C5α,C10β half-chair conformation. The six-membered rings B, C, and F have chair conformation as expected. The D ring adopts a C14α-envelope conformation and the E ring is midway between a C22α,O3β half-chair and a C22α-envelope conformations. The A/B, B/C, and C/D ring junctions are trans. Crystal data: C27H38O5·1/2C4H8O2, Monoclinic, space group P21, a = 7.7363(18) b = 28.769(12) c = 12.038(6) Å, β = 90.88(5), V = 2679.0(10) Å3, Z = 4. The packing of the molecules is assumed to be dictated by van der Waals interactions and by intermolecular C—H ··· O hydrogen bonds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012277425969
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  • 8
    Electronic Resource
    Electronic Resource
    X-ray crystal structure of trans-bis(monoethanolamine) bis(saccharinato)nickel(II) (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 767-771 
    Details
    ISSN: 1572-8854
    Keywords: saccharin ; monoethanolamine ; nickel(II) complex ; hydrogen bonding ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of trans-bis(monoethanolamine)bis(saccharinato)nickel(II), [Ni(C7H4NO3S)2(C2H7NO)2], has been determined from X-ray diffraction data. The metal complex is monoclinic, with a = 11.0555(5), b = 8.9103(4), c = 11.3890(5) Å, β = 105.0230(10)°, Z = 2, and space group P21/c . The structure consists of individual molecules. Two monoethanolamine molecules and two saccharinate anions coordinate the nickel atom forming a distorted octahedron. The monoethanolamine molecules act as a bidentate ligand and form five-membered trans chelate rings, which constitute the plane of the coordination octahedron, while two saccharinate ions behave as a monodentate ligand occupying the axial positions. Intermolecular hydrogen bonds link the molecules to form a three-dimensional infinite structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013292406687
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  • 9
    Electronic Resource
    Electronic Resource
    Novel Cu–Te Clusters Synthesised from tBuTeSiMe3: [Cu18Te6(TetBu)6(PPh2Et)7], [Cu19Te6(TetBu)7(PEt3)8], [Cu27Te15(PiPr2Me)12] and [Cu58Te32(PtBu2nBu)14] (2000)
    Springer
    Journal of cluster science 11 (2000), S. 135-151 
    Details
    ISSN: 1572-8862
    Keywords: copper telluride clusters ; copper telluro-tellurolato clusters ; crystal structure ; influence of phosphine ligands ; Frank-Kasper polyhedron
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The reactions of CuCl and tBuTeSiMe3 in the presence of phosphine ligands result in the formation of four new Cu/Te cluster complexes, [Cu18Te6(TetBu)6(PPh2Et)7], [Cu19Te6(TetBu)7(PEt3)8], [Cu27Te15(PiPr2Me)12] and [Cu58Te32(PtBu2 nBu)14], which have been structurally characterized by single crystal structural analysis. The former two clusters show a layer-type tellurium frameworks in which the copper atoms are asymmetrically spread. The latter two clusters possess a tellurium framework in a body-centered Te14-Frank-Kasper polyhedron or a Te28 polyhedron with four interstitial tellurium atoms and belong to mixed-valence Cu/Te compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009016832159
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  • 10
    Electronic Resource
    Electronic Resource
    Cluster Build-up Reactions using Di-gold Cationic Fragments: Synthesis and Structural Characterization of [Os7(CO)19(Au2dppm)] (2000)
    Springer
    Journal of cluster science 11 (2000), S. 217-226 
    Details
    ISSN: 1572-8862
    Keywords: gold ; osmium ; cluster ; carbonyl ; phosphine ; heteronuclear ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The reaction of the di-gold cation [Au2(dppx)]2+ with the heptanuclear cluster dianion [Os7(CO)20]2− affords the mixed metal cluster [Os7(CO)20{Au2(dppx)}] (x=m (1), e (2), b (3)). On standing, in solution, this complex undergoes decarbonylation to give the cluster [Os7(CO)19{Au2(dppx)}] (x=m (4), e (5), b (6)). The complexes have been characterised spectroscopically, and an X-ray structure determination of the dppm derivative shows that it contains a metal core based on an Os7 edge-bridged bicapped tetrahedron with the two μ 3-Au atoms capping adjacent triangular Os3 faces of the central tetrahedron. In an analogous reaction, the carbido anion [Os7(H)C(CO)19]− affords the neutral cluster [Os7C(CO)19{Au2(dppm)}] (7) when treated with [Au2(dppm)]2+ in the presence of base.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009025101208
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  • 11
    Electronic Resource
    Electronic Resource
    Crystal structure of 2,2,3-trimethyl-3-(2′,4′,5′-tricyanophenyl) cyclopentyl-1-acetic acid, methyl ester, C20H21N3O2 (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 589-592 
    Details
    ISSN: 1572-8854
    Keywords: Phenylcyclopentaneacetate derivative ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound crystallizes in space group P21/n, with a = 14.600(2), b = 7.091(2), c = 18.211(5) Å, and β = 103.67(2)°. Owing to the centric space group, both C(1) and C(3) chiral centers are either R or S. The acetate group is equatorial, the H(1) and the methyl group at C(3) are axial and reciprocally trans.
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    URL: http://dx.doi.org/10.1023/A:1011358327087
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  • 12
    Electronic Resource
    Electronic Resource
    The crystal and molecular structure of spiro[1-(S)-Br-3-(S)-H-4-(R)-l-(1′ R,2′ S,5′R)-menthyloxy-5-oxo-6-oxa-bicyclo[3.1.0]hexane-2,3′-(R)-(4′-(R)-diphenylmethoxy-5′-l-(1′ R,2′ S,5′ R)-menthyloxy-butyrolactone)] (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 737-741 
    Details
    ISSN: 1572-8854
    Keywords: crystal structure ; asymmetric synthesis ; spiro-cyclopropane derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Crystal structure of C41H53O7Br has been determined by single-crystal X-ray diffraction. The compound crystalline in the orthorhombic space group P212121, with a = 11.264(2), b = 12.058(2), c = 29.337(6) Å, Z = 4. The bond angles of cyclopropane moiety in the molecule are approximate to 60° and agree with theoretic values of the internal angles in a cyclopropane, and two chiral menthyloxy groups are located above and under the whole chiral molecule, respectively. The configuration of the pentacyclic lactone is shown as envelope form.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012254312765
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  • 13
    Electronic Resource
    Electronic Resource
    Structural Redetermination of Rh4(CO)12 at 293 and 173 K and Analysis of the Thermal Motion in Relation to the Dynamical Behavior (2000)
    Springer
    Journal of cluster science 11 (2000), S. 39-53 
    Details
    ISSN: 1572-8862
    Keywords: thermal motion ; crystal structure ; rhodium carbonyl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The structure of Rh4(CO)12 (1) has been redetermined at room temperature and at 173 K. Crystallographic data for 1 at 293 K are as follows: C12O12Rh4, space group P21/c, a=9.209(3), b=11.790(7), c=17.721(8) Å, β=90.46(3)°, V=1924.0(16) Å3, Z=4, 5570 reflections to θ=30.0°, and R=0.030. For 1 at 173 K the data are as follows: space group P21/c, a=9.127(3), b=11.672(6), c=17.492(13) Å, β=90.64(5)°, V=1863.3(18) Å3, Z=4, 3782 reflections to θ=26.3°, and R=0.033. There was no detectable phase change on cooling to 173 K. Crystals of 1 are twinned by pseudo-merohedry, but a satisfactory refinement was obtained by assuming a (100) twinning mirror plane. TLS analysis of the anisotropic displacement parameters at both temperatures has been undertaken. Investigation of the mean square displacement difference between the observed and the rigid body displacement parameters reveals there is a signficant internal motion of the carbonyl ligands relative to the metal skeleton. This motion is consistent with a normal mode or modes of C 3 symmetry.
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    URL: http://dx.doi.org/10.1023/A:1009000428525
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  • 14
    Electronic Resource
    Electronic Resource
    A Novel Cluster Consisting of Seven Fused MX6 Octahedra, Li14(THF)8[Ni7Cl17(μ-formamidinate)3(μ-Cl)]2 (2000)
    Springer
    Journal of cluster science 11 (2000), S. 87-94 
    Details
    ISSN: 1572-8862
    Keywords: nickel cluster ; fluorinated formamidine ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract When a THF solution made from equimolar amounts of methyllithium and N,N′-bispentafluorophenyl formamidine, C6F5NC(H)N(H)C6F5, was added to a suspension of NiCl2 in THF and the mixture refluxed for 12 h, a bright yellow-green solution was formed, from which a bright green crystalline compound was obtained in 〉60% yield upon partial evaporation of the solvent. This compound, Li14(THF)8[Ni7Cl17(μ-formamidinate)3(μ-Cl)]2·9.4THF, crystallizes in the tetragonal space group P4 2/mnm (No. 136) with Z=2. The core consists of two Ni7 units bridged by two Cl atoms.
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    URL: http://dx.doi.org/10.1023/A:1009008630342
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  • 15
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    Electronic Resource
    Organically Templated Vanadium Oxide Phases: Synthesis and Structures of [H3NCH2CH2NH3][V2O6] and [HN(CH2CH2)3NH][VV2VIV4O14]·H2O (2000)
    Springer
    Journal of cluster science 11 (2000), S. 433-447 
    Details
    ISSN: 1572-8862
    Keywords: crystal structure ; vanadium oxide ; organic template ; mixed valence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The synthesis and crystal structures of [H3NCH2CH2NH3][V2O6] (1) and [HN(CH2CH2)3NH][VV 2VIV 4O14]·H2O (2) are described. The structure of the oxidized compound 1 consists of parallel stacks of vanadium oxide chains of corner sharing {VO4} tetrahedra. The chains are stabilized by extensive hydrogen bonding involving oxide ligands of the chains and ethylenediammonium ions which fill the space between the stacks of chains. The structure of compound 2 consists of vanadium oxide layers separated by doubly protonated 1,4-diazabicyclo[2.2.2]octane and lattice water. The vanadium oxide layers, containing mixed-valence vanadium (VV and VIV) centers, are composed of zigzag ribbons of edge-sharing {VO5} square pyramids interconnected by {VO4} tetrahedra. Crystal data. C2H10N2O6V2 , 1: monoclinic, space group P21/c (No. 14), a=5.5359(5), b=12.9430(12), c=5.6856(5) Å, α=90, β=97.460(2), γ=90°, V=403.93(6) Å3, Z=2. A total of 2506 reflections (θ max=27.89°) was collected, of which 954 were used to resolve the structure. The structure was solved by direct methods and least-squares refinement converged at R=0.0592. C6H16N2O15V6, 2: monoclinic, space group C2 (No. 5), a=19.303(4), b=6.667(2), c=7.579(2) Å, α=90, β=111.31(2), γ=90°, V=908.4(4) Å3, Z=2. A total of 1779 reflections was collected, of which 1591 unique reflections were used for structural elucidation. The structure was solved by direct methods and least-squares refinement converged at R=0.0314.
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    URL: http://dx.doi.org/10.1023/A:1009051500265
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  • 16
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    Electronic Resource
    Crystal and molecular structure studies of tris(2-hydroxy-3-t-butyl-5-methylbenzene)-methane trihydrate and N-benzyl-N-phenyl benzamide (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 255-258 
    Details
    ISSN: 1572-8854
    Keywords: THBMBM ; BPB ; crystal structure ; helical packing ; columnar packing ; mesophase transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structures of the title compounds, tris(2-hydroxy-3-t-butyl-5-methylbenzene)-methane)C34H46O3.3H2O, 3) and N-benzyl-N-phenylbenzamide (C20H17NO, 6), have been investigated by X-ray crystallography. Compound 3 crystallizes in the trigonal space group $$P\bar 3 $$ with cell parameters a = 14.090(5) Å, b = 14.090(5)Å, c = 10.485(5)Å, Z = 2. Compound 6 crystallizes in the monoclinic space group C2/c with cell parameters a = 24.533(4)Å, b = 9.176(4)Å, c = 16.711(5)Å, β = 125.88(2)°, Z = 8. Compound 3 has both intra-and intermolecular hydrogen bonds. It also exhibits a helical columnar arrangement of the molecules and goes into mesophase before melting into an isotropic liquid.
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    URL: http://dx.doi.org/10.1023/A:1009595123416
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  • 17
    Electronic Resource
    Electronic Resource
    Synthesis and crystal structure of 4-(p-methoxyphenyl)-3, 5-bis(4-pyridyl)-1,2,4-triazole (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 429-432 
    Details
    ISSN: 1572-8854
    Keywords: Triazole ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The 4-(p-methoxyphenyl)-3,5-bis(4-pyridyl)-1,2,4-triazole has been synthesized and its crystal structure has been determined by X-ray diffraction methods. It crystallizes in the monoclinic space group P21/n, with a = 12.5832(6) Å, b = 7.0512(5) Å, c = 18.4669(12) Å, β = 96.826(1)°, and Dcalc = 1.345 g cm−1 for Z = 4. In the structure, two pyridyl rings, phenyl ring, and triazole ring do not share a common plane. The most favored orientation of the pyridyl rings in the crystal is that their planes are inclined toward opposite directions with respect to the triazole ring.
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    URL: http://dx.doi.org/10.1023/A:1009542208264
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  • 18
    Electronic Resource
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    Crystal structure and spectroscopy of the low-spin iron(II) compound: tris(bipyrimidine)iron(II) bis(triflate), [Fe(bipym)33](CF3SO3)2 (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 441-444 
    Details
    ISSN: 1572-8854
    Keywords: 2,2′-Bipyrimidine ; low-spin ; iron ; crystal structure ; infrared
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The compound [Fe(bipym)33](CF3SO3)2 (in which bipym = 2,2′-bipyrimidine) crystallizes in the space group P21/c, with a = 13.7641(11), b = 18.7557(19), c = 12.3627(11) Å, β = 103.085(8)° and Z = 4. The low-spin Fe(II) atom is octahedrally surrounded by six nitrogen atoms of three bipyrimidine groups with Fe—N distances that vary from 1.968(4) to 1.975(4) å. In the far-infrared region the Fe—N vibrations are observed at 359 and 372 cm-1.
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    Crystal structure of a novel bis(guanidiniums) compound incorporated by sulfate anion (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 483-487 
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    ISSN: 1572-8854
    Keywords: Bis(guanidiniums) ; sulfate anion ; hydrogen bond ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Crystal structure of a novel bis(guanidiniums) compound 1 by sulfate anion and water, C11H20N6OċSO4ċH2O, was measured by X-ray crystallographic analysis with an “imaging plate” method. It possesses space group P21/c, with a = 7.6433(15), b = 19.447(4), c = 12.115(2) Å, β = 107.81(3)°, and φcalc = 1.420 mg/m3 for Z = 4. Crystal data indicate that the architecture network is formed through hydrogen bonds, electrostatic interactions, and arene–arene stacking interaction among the bis(guanidiniums) compound, the sulfate anion and water molecule.
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    Redetermination of the structure of bis[chloro-2-(2-hydroxy-4,5-dimethylphenylazo)-5,5-dimethyl-4,5,6,7-tetrahydrobenzothiazol-7-on] copper(II) complex (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 505-507 
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    ISSN: 1572-8854
    Keywords: Bis[chloro-2-(2-hydroxy-4,5-dimethylphenylazo)-5,5-dimethyl-4,5,6,7-tetrahydrobenzothiazol-7-on]copper(II) ; thiazolylazo dye ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of C17H18ClCuN3O2S (M = 854.78, monoclinic, P21/c, a = 8.316(2), b = 18.461(4), c = 11.774(2) Å, β = 99.64(3)°, V = 1782.0(7) Å3, Z = 4) is formed by dimeric molecules [C17H18ClCuN3O2S]2 with two monomeric units linked together by two chlorine atoms. The Cu atom is coordinated by two chlorine atoms, an oxygen atom, the azo nitrogen atom attached to the benzene ring, and the nitrogen atom of the thiazole ring, in the form of a distorted tetragonal pyramid.
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    Synthesis and crystal structure of the perchlorate salt of diprotonated N,N′-bis(1-methylimidazole-2-methyl)1,5-diazacyclooctane (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 531-534 
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    ISSN: 1572-8854
    Keywords: 1,5-Diazacyclooctane (DACO) ; crystal structure ; boat/chair configuration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The diprotonated perchlorate salt of a new 1,5-diazacyclooctane (DACO) mesocycle functionalized by two imidazole pendants, N,N′-bis(1-methylimidazole-2-methyl)-1,5-diazacyclo-octane (C16H28N6Cl2O8), has been synthesized and the structure determined by X-ray diffraction analysis. The title compound crystallizes in the monoclinic system, space group P21/c with a = 11.964(2), b = 13.251(3), c = 14.741(3) Å, β = 106.00(3)°, Mr = 503.34, V = 2246(1) Å3, Z = 4. The crystal structure of the title compound reveals that the DACO ring is also folded up into the “chair/boat” configuration, which is consistent with the configuration in most of the transition metal complexes of DACO and its derivatives. The two imidazole pendants of the compound are in cis position with a dihedral angle of 16.0(4)°.
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    Structural and spectroscopic characterization of tris (o-phenanthroline)iron(II) disaccharinate monosaccharin hexahydrate (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 539-544 
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    ISSN: 1572-8854
    Keywords: Iron(II) ; o-phenanthroline ; saccharinate ; crystal structure ; spectroscopic properties ; thermal behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of the title compound, for short [Fe(o-phen)3](sac)2·(Hsac)·6H2O, has been determined by X-ray diffraction methods. It crystallizes in the monoclinic space group P21/n with a = 16.3190(1), b = 19.2890(1), c = 17.4490(2) Å, β = 92.586(1)°, V = 5486.95(8) Å3 and, Z = 4. The investigated compound constitutes the first example of a species in which uncoordinated saccharin and saccharinate anions are present in the structure. The crystallographic results reveal the subtle differences between the structure of the neutral molecule and its anion. The complex was also characterized by means of infrared, electronic, and 57Fe-Mössbauer spectroscopy. Its magnetic susceptibility was determined at room temperature and its thermal behavior investigated by means of thermogravimetric and differential thermal analytical techniques.
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    Synthesis and X-ray structure of [(H3O)(C14H20O5)2][Me2NH2]2 [PMo12O40] · 2C14H20O5 (C14H20O5 = benzo-15-crown-5; Me2NH = dimethylamine) (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 577-581 
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    ISSN: 1572-8854
    Keywords: Oxonium ions ; crystal structure ; molybdophosphate ; crown ether
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract [(H3O)(C14H20O5)2][Me2NH2]2 [PMo12O40] · 2C14H20O5 1 was synthesized from benzo-15-crown-5 and H3PMo12O40·24H2O in N,N′-dimethylformamide for the first time. 1 crystallizes in the monoclinic space group C2/c with a = 18.583(4), b = 25.510(5), c = 19.904(4) Å, β = 94.66(3)° D c = 2.124 mg/m3 for Z = 4. Refinement based on 7358 observed reflections led to a R1(wR2) = 0.0378(0.0761). The complex cation, [(H3O)(C14H20O5)2]+, exhibits a sandwich structure by hydrogen-bonding in the mean distance of 2.955 Å. The anion, PMo12O40 3−, is a α-Keggin structure.
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    Synthesis, spectroscopy, and X-ray structure of the polymer catena-[bis(azido-N)-copper(II)-μ-bis(2-benzimidazolyl)butane] (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 69-72 
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    ISSN: 1572-8854
    Keywords: azido ; crystal structure ; copper(II) ; infrared ; polymeric
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound, catena-[bis(azido-N)-copper(II)-μ(bis(2-benzimidazolyl)butane), [Cu(C18H18N4)(N3)2]n, was obtained from the reaction of the ligand bis(2-benzimidazolyl)butane and Cu(N3)2. The x-ray crystal structure is reported. The compound crystallizes in the monoclinic space group P21/c with a = 8.2524(10), b = 12.765(5), c = 9.1125(15) Å, β = 106.423(12)°, Z = 2. The Cu(II) ions are square-planar coordinated with trans-oriented end-on binding azido ligands. The structure is a polynuclear chain with the benzimidazole bridging at each end. In addition a N(ligand)-H···N(azido) H-bridge [N(ligand)···N(azido) = 2.994(7) Å] is present, resulting in a pseudo 2-dimensional lattice. The characteristic azido infrared vibrations are found at 2060 and 2077 cm−1 (νas(N3)) and 1284 and 1297 cm−1 (ν(N3)).
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    Synthesis and crystal structure of [Tb4(H2O)2](C2O4)2(C5H6O4)4 (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 633-639 
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    ISSN: 1572-8854
    Keywords: Lanthanide ; oxalate ; glutarate ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A terbium complex associating two ligands, oxalate and glutarate, was prepared under hydrothermal conditions at 200°C by treating an aqueous suspension of terbium oxalate decahydrate with glutaric acid and guanidinium carbonate. Its structure was solved by X-ray diffraction on a single crystal. It crystallizes in the monoclinic space group P21 with lattice constants, a = 9.514(1) Å, b = 9.0681(8) Å, c = 19.702(2) Å, and β = 97.90(1)°. The terbium atoms and the oxalate ligands build dense chains which are connected by one side of the carboxylic group of some glutarate ligands, thus forming a sheet at the c level ≅ 0 and 1/2. These sheets are bridged by glutarate groups. The terbium atoms are ninefold coordinate with nine oxygen atoms of the ligands or with one water molecule and eight oxygen atoms of the ligands. Each polyhedron of the terbium atoms share one edge and one face of oxygen atoms with the two neighboring ones. The oxalate ligands are bischelating and bismonodentate. The coordination scheme of glutarate differs: either they are bismonodentate from one side and chelating and monodentate from the other side or they are chelating and monodentate from both sides.
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    Terbium and holmium trans-2,3-dimethylacrylic acid complexes with 1,10-phenanthroline (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 777-782 
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    ISSN: 1572-8854
    Keywords: terbium complex ; holmium complex ; crystal structure ; trans-2,3-dimethylacrylic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Novel dinuclear complexes, [REL3(phen)]2 (where RE = Tb, Ho; HL = trans-2,3-dimethylacrylic acid; phen = 1,10-phenantheoline), were synthesized and determined by elemental analysis, infrared absorption spectra (IR), thermogravimetric analysis (TGA), and X-ray diffraction. The Tb complex crystallizes in space group P21/n with the cell dimensions a = 12.939(2) Å, b = 13.018(2) Å, c = 15.400(3) Å and β = 94.72(1)°. The Ho complex crystallizes in P (9) with a = 12.406(3) Å, b = 13.280(3) Å, c = 9.823(2) Å, α = 110.80(2)°, β = 103.42(2)°, γ = 63.67(1)°. The Tb atom is nine coordinate and the separation of Tb...Tb* is 3.97 Å. The Ho atom is eight coordinate and the separation of Ho...Ho* is 4.01 Å.
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    Synthesis and crystal structure of 1-(1′,3′-dimethyl-5′-chloropyrazol-4′-carbonyl′-3-(2′-chlorophenyl)-5-amino-4-cyanopyrazole (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 789-792 
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    ISSN: 1572-8854
    Keywords: crystal structure ; pyrazolide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound 1-(1′,3′-dimethyl-5′-chloropyrazol-4′-carbonyl)-3-(2′-chlorophenyl)-5-amino-4-cyanopyrazole (C16H12Cl2N6O) has been synthesized and characterized by X-ray diffraction: Triclinic, space group P1, with a = 8.6712(8) Å, b = 9.5091(10) Å, c = 11.2170(11) Å α = 71.531(2)°, β = 84.683(2)°, γ = 74.099(2)° Z = 2; V = 843.7(14) Å3. C(10), O(1), C(11), and N(2) atoms are coplanar with the average deviation of 0.0071 Å, which form 11.03° and 43.93° dihedral angles with pyrazole planes (I) and (II), respectively.
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    URL: http://dx.doi.org/10.1023/A:1013224308504
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    Structure, thermal behavior, and IR investigation of bis(3-amino-1,2,4-triazolium)monohydrogen monophosphate (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 805-809 
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    ISSN: 1572-8854
    Keywords: organic phosphate ; crystal structure ; DTA/TG/DSC ; IR spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Chemical preparation, calorimetric studies, crystal structure, and IR spectrometric investigation of (C2H5N4)2HPO4, denoted ATZP, are described. The compound crystallizes in the monoclinic system with C2/c space group. Its unit cell dimensions are a = 13.589(2) Å b = 11.105(2) Å c = 15.734(3) Å β = 104.68(2)°, V = 2296.8(7) Å3, and Z = 8. The structure of the title compound consists of a three dimensional network of H-bonds connecting all its components. The IR spectrum of ATZP is reported and discussed on the basis of group theoretical analysis.
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    Crystal structure of [WI2(CO)2{P(OiPr)3}(η2-EtC2Et)] (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 181-184 
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    ISSN: 1572-8854
    Keywords: tungsten(II) ; diiodo ; dicarbonyl ; triisopropylphosphite ; 3-hexyne ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract [WI2(CO)2{P(OiPr)3}(η2-EtC2Et)] crystallizes in the monoclinic space group P21/n, with a = 11.101(12), b = 16.272(18), c = 14.892(17) Å, β = 93.27(1), Z = 4. The geometry can be considered to be pseudo-octahedral, with the 3-hexyne ligand occupying one site, with two iodo-groups, and the P(OiPr)3 ligand completing the equational plane of ligands, with two trans-carbonyl groups occupying the axial sites.
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    Synthesis, crystal structure and molecular modeling (AM1) of two 5-arylidene derivatives of Meldrum's acid (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 189-194 
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    ISSN: 1572-8854
    Keywords: crystal structure ; AM1 ; x-ray diffraction ; Meldrum's acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The synthesis and structural characterization of two 5-Arylidene derivatives of Meldrum's acid (2,2-dimethyl-1,3-dioxane-4,6-dione) are described: 5-(4-Nitrobenciliden)-2,2-dimethyl-1,3-dioxane-4,6-dione (3a), and 5-(4-Methoxybenciliden)-2,2-dimethyl-1,3-dioxane-4,6-dione (3b). The structure of 3a was refined to R1 = 0.0421 for 2148 reflections (with I 〉 2σ (I)). Crystal data for 3a: C13H11NO6, orthorhombic, space group Pbca, a = 16.008(3), b = 6.137(1), c = 25.281(5) Å, V = 2483.6(8) Å3, Z = 8. The structure of 3b was refined to R1 = 0.0496 for 4681 reflections (with I 〉 2σ(I)). Crystal data for 3b: C14H14O5, triclinic, space group P1, a = 9.131(2), b = 9.922(2), c = 14.490(3)Å, α = 85.076(6), β = 84.80(3), γ = 89.37(2)°,V = 1302.4(5) Å3, Z = 4. The results of crystallographic and molecular modeling (AM1) were compared. The molecules in the crystal are held together, in both compounds, by van der Waals forces and C—H···O hydrogen bond interactions.
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    Separation of rosin acids by molecular recognition: crystal structure of the complex of neoabietic acid with 2-amino-6-methyl-pyridine (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 195-198 
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    ISSN: 1572-8854
    Keywords: neoabietic acid ; amino(methyl)pyridine ; crystal structure ; molecular recognition ; H-bonding ; rosin acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Neoabietic acid has been separated from gum rosin mixture by the aid of molecular recognition using 2-amino-6-methyl-pyridine as recognition reagent. The complex of neoabietic acid with 2-amino-6-methy-pyridine crystallizes from ether solution in the monoclinic, space group P21 with cell parameters of a = 7.370(1), b = 8.692(1), c = 18.365(2) Å, β = 92.53(1)°,V = 1175.3(2) Å3 and Z = 2. X-ray structure analysis shows that an extensive H-bonding network exists between neoabietic acid and amino(methyl)pyridine, which is considered as one of the factors resulting in successfully separating the neoabietic acid from the gum rosin mixture.
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    Crystal structure of a novel tertiary phosphine coordination complex: dichlorobis(tribenzylphosphine)nickel(II) (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 173-176 
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    ISSN: 1572-8854
    Keywords: phosphine ; nickel(II) complexes ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound dichlorobis(tribenzylphosphine)nickel(II), Ni[P(CH2C6H5)3]2Cl2, belongs to a type of tertiary phosphine coordination complex, M(PR3)2X2. There are two molecules in the unit cell which do not appear to interact chemically. Both molecules have a trans-square planar configuration with each nickel atom on a center of symmetry. Three benzyl groups are bonded to each phosphorus atom as rotors in a propeller, and the threefold axis is along the P—Ni bond, which has a mean length of 2.23(1) Å. Crystal data: C42H42Cl2NiP2, Triclinic, space group $$P\bar 1 $$ , a = 10.4892(15) b = 10.5249(12) c = 19.453(2) Å, α = 83.872(8), β = 76.839(9), γ = 62.241(8)°, V = 1850.5(4) Å3, Z = 2. There is an intramolecular hydrogen bond between the C3 and C11 atoms.
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    Why Does the Linear Driving Force Model for Adsorption Kinetics Work? (2000)
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    Adsorption 6 (2000), S. 137-147 
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    ISSN: 1572-8757
    Keywords: adsorption ; kinetics ; linear driving force model ; process design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The Linear Driving Force (LDF) model for gas adsorption kinetics is frequently and successfully used for analysis of adsorption column dynamic data and for adsorptive process designs because it is simple, analytic, and physically consistent. Yet, there is a substantial difference in the characteristics of isothermal batch uptake curves on adsorbent particles by the LDF and the more rigorous Fickian Diffusion (FD) model. It is demonstrated by using simple model systems that the characteristics of the adsorption kinetics at the single pore or the adsorbent particle level are lost in (a) evaluating overall uptake on a heterogeneous porous solid, (b) calculating breakthrough curves from a packed adsorbent column, and (c) establishing the efficiency of separation by an adsorptive process due to repeated averaging of the base kinetic property. That is why the LDF model works in practice.
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    Effect of K, Cs and Ba on the kinetics of NH3 synthesis over carbon-based ruthenium catalysts (2000)
    Springer
    Catalysis letters 68 (2000), S. 163-168 
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    ISSN: 1572-879X
    Keywords: ammonia synthesis ; kinetics ; ruthenium catalysts ; promotional effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of NH3 synthesis over carbon-based ruthenium catalysts promoted with barium or alkali was studied. Both the ammonia partial pressure dependencies of the reaction rates (T = 400°C, p = 63 bar, H2 : N2 = 3 : 1) and the pressure variations of the activity (T = 370°C, p= 4–63 bar, H2 : NN2 = 3 : 1) were found to be different for Ba and for the alkali (K, Cs). Ba–Ru/C proved to be more sensitive to the NH3 content and to the total pressure. The rate of synthesis over the alkali-promoted catalysts is, in turn, much stronger influenced by the ruthenium dispersion. TOFs of NH3 synthesis for the promoted samples at 370°C and 4 bar (Ba 0.085 1/s, Cs 0.05 1/s, K 0.035 1/s) are significantly higher than that for the Ru(0001) basal plane (0.0085 1/s results from the literature data at 370°C, 2 bar). The most active Ru/C samples (Ba or Cs) exceed significantly the fused iron catalyst, especially at high conversions.
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    A dinuclear cyanide-bridged complex, [(DMF)4(H2O)3LuCo(CN)6]·H2O (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 671-675 
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    ISSN: 1572-8854
    Keywords: Synthesis ; crystal structure ; lutetium(III) ; cobalt(III) hexacyanide ; cyanide bridging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of the bimetallic cyanide bridged complex [(DMF)4(H2O)3LuCo(CN)6]·H2O (1) was obtained by single-crystal X-ray diffraction. The central lutetium(III) ion is eight coordinate arranged in a square antiprism while the cobalt(III) ion is six coordinate, oriented octahedrally. Molecules in the crystal lattice are held together by a network of hydrogen bonding. Crystallization of 1 occurs in the centrosymmetric monoclinic space group P21/c (No. 14) with a = 13.875(2), b = 8.8352(9), c = 24.633(2) Å β = 96.392(8)° and Z = 4.
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    Identification of a new family of diphosphate compounds, AI2BII3(P2O7)2: Structures of Ag2Co3(P2O7)2, Ag2Mn3(P2O7)2, and Na2Cd3(P2O7)2 (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 705-716 
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    ISSN: 1572-8854
    Keywords: mixed metal diphosphates ; AI 2BII 3(P2O7)2 ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Syntheses and single-crystal X-ray structural results are reported for three new mixed diphosphates of the family AI 2BII 3(P2O7)2; Ag2Co3(P2O7)2 (I), Ag2Mn3(P2O7)2 (II), and Na2Cd3(P2O7)2 (III). All crystallize in the triclinic system, space group P1 bar: (I) a = 5.351(4), b = 6.375(4), c = 16.532(4) Å, α = 80.83(6) β = 81.45(4), γ = 72.87(5)°, V = 528.9(6) Å3, Z = 2, D calc = 4.649 mg/m3, R/Rw = 0.0428/0.0548 for 3949 obs. reflns; (II) a = 5.432(7), b = 6.619(6), c = 16.51(3) Å, α = 80.78(8) β = 82.43(9), γ = 72.82(7)°, V = 557.7(13) Å3, Z = 2, D calc = 4.338 mg/m3, R/Rw = 0.0679/0.1303 for 2100 obs. reflns and (III) a = 5.67(3), b = 7.08(4), c = 7.90(4) Å, α = 77.0(2), β = 82.5(2), γ = 67.8(2)°, V = 286(3) Å3, Z = 2, D calc = 4.249 mg/m3, R/Rw = 0.0307/0.0342 for 1945 obs. reflns. (I) and (II) are isostructural but (III) is of a different type. All three structures are characterized by layers of P2O7 groups alternating with layers of mixed metal atoms. Differences are seen in the conglomerate bonding patterns of B atoms and in the irregular geometry of Ag in (I) and (II) compared to the octahedral bonding seen for Na in (III). The differences in structure may be understood in terms of the ratios of the ionic radii of A and B atoms.
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    Crystal structure of diethoxynitrobenzene-p-tert-butylcalix [4]arene⋅2(CH3)2C=O: Evidence of intra- and intermolecular CH/π interactions forced by crystal packing (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 717-720 
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    ISSN: 1572-8854
    Keywords: calix[4]arene ; CH/π interaction ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Diethoxynitrobenzene-p-tert-butylcalix[4]arene⋅2(CH3)2C=O crystallized in the monoclinic system, space group P21/c, with cell dimensions a = 16.1437(2) Å, b = 21.0292(2) Å, c = 18.9685(3) Å and β = 110.308(1)°. The asymmetric unit consists of a diethoxynitrobenzene-p-tert-butylcalix[4]arene molecule and two solvated acetone molecules. Besides the usual CH/π interaction between p-tert-butylcalix[4]arene π cavity and a solvated acetone, this structure shows the intra- and intermolecular CH/π interactions among a nitrobenzene ring, ethylene bridge of the ethoxynitrobenzene side chain and a solvated acetone molecule.
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    Crystal structure of a 26-membered hexaaza macrocycle bearing hydroxyethyl pendants containing p-xylyl spacers (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 743-747 
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    ISSN: 1572-8854
    Keywords: macrocycle ; hydroxyethyl pendant ; crystal structure ; hydrogen bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The new macrocyclic compound bearing hydroxyethyl pendant arms containing p-xylyl spacers, 3,6,9,16,19,22-hexaaza-6,19-bis(2-hydroxyethyl)-tricyclo[22,2,2,211,14] triaconta-1,11,13,24,27,29-hexaene, crystallizes in the monoclinic space group P21/c with a = 8.700(2) Å, b = 18.301(4) Å, c = 11.766(2) Å, β = 108.57(2)°. The two hydroxyethyl pendants are at the opposite sides of the macrocyclic plane. Benzene rings in macrocycle are parallel and exist the π-π weak interaction with distance of 4.28 Å. The crystal packing of the macrocycle is stabilized by the hydrogen bonds.
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    Crystal structure, thermal analysis, and IR spectrometric investigation of bis(tert-butylammonium) sulfate (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 799-804 
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    ISSN: 1572-8854
    Keywords: organic sulfate ; crystal structure ; DTA/TG/DSC ; IR spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Chemical preparation, X-ray single crystal, thermal analysis, and IR spectrometric investigation of (C4H12N)2SO4, denoted tBAS, are described. The compound crystallizes in the monoclinic system with C2/c space group. Its unit cell dimensions are a = 11.1585(5) Å, b = 6.2148(4) Å, c = 20.070(1) Å, β = 102.004(4)°, V = 1361.4(1) Å3, and Z = 4. The crystal structure of tBAS can be described as a typical thick layered organization built by all the components of the structure and centered by planes z = 1/4 and 3/4. Connection in these layers are established by N—H···O hydrogen bonds. Thermal analysis shows a reversible weak phase transition.
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    Crystal structure and spectroscopy of bis-[bis(2-benzimidazolyl)propane]copper(II) bis(triflate)monohydrate, a copper complex with a geometry intermediate between tetrahedral and square planar (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 793-797 
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    ISSN: 1572-8854
    Keywords: copper ; bis(benzimidazoles) ; crystal structure ; infrared
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure of a mononuclear copper(II) compound with the ligand bis(2-benzimidazolyl)propane (abbreviated as tbz) is reported. The compound [Cu(tbz)2](CF3SO3)2(H2O) crystallizes in the triclinic space group P $$\bar 1$$ , with a = 12.363(6), b = 13.218(9), c = 15.365(8) Å, α = 82.74(5), β = 68.04(4), γ = 65.30(5), and Z = 2. The Cu(II) atom has a geometry intermediate between tetrahedral and square planar, consisting of four nitrogen atoms of two tbz ligands. The Cu—N—Cu angles are about 135°, while the dihedral angle between them amounts to 62° (0° for square planar and 90° for a tetrahedron). Ligand field bands are observed at 10.2 × 103, 13.8 × 103, and 20.3 × 103 cm−1, while the most characteristic infrared vibrations of the triflate anion are observed at 1273, 1260, 1238, 1221, 1171, and 1157 cm−1.
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    Crystal structure and thermal analysis of 1,5-diammonium-2-methyl pentane sulfate monohydrate (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 95-98 
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    ISSN: 1572-8854
    Keywords: organic sulfate ; crystal structure ; DTA/TG/DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Chemical preparation, x-ray single crystal, and thermal analysis of C6H18N2SO4·H2O (denoted DMPS) are described. The compound crystallizes in the triclinic system with P $$\overline 1$$ space group. Its unit cell dimensions are a = 5.826(1) Å, b = 10.014(1) Å, c = 11.221(1) Å, α = 66.716(1)°, β = 84.395(1)°, γ = 83.759(1)°, V = 596.7(1) Å3, and Z = 2. The DMPS structure is built up from inorganic chains parallel to the a axis and linked via O(W)-H···O hydrogen bonds. These chains are interconnected by organic groups. Thermal analysis reveals the presence of one water molecule in the structure and shows a reversible weak phase transition.
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    Molecular structure and 1H, 13C NMR assignments of 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 115-118 
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    ISSN: 1572-8854
    Keywords: 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene (titmb); crystal structure; hydrogen bonding; 2D NMR ; crystal structure ; hydrogen bonding ; 2D NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The molecule 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene (titmb) crystallizes as a monohydrate in the monoclinic space group C2/c with a = 20.888(4), b = 13.220(2), c = 14.385(2) Å, β = 90.36(1)°. Two of three imidazole groups are on one side of the central benzene ring, and the other one is on the opposite side. The crystal packing of titmb is stabilized by O-H--N hydrogen bonding between the water molecule and nitrogen atoms of the imidazole group. The complete 1H and 13C NMR assignments for titmb were carried out by 2D NMR spectral measurements.
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    Crystal structure of 2,6-dimethylpyridinium hydrogen phthalate (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 119-122 
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    ISSN: 1572-8854
    Keywords: phthalic acid ; 2, 6-dimethylpyridine ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A new crystal of 2,6-dimethylpyridinium hydrogen phthalate (DPMHP) has been prepared and characterized by x-ray crystallography. DPMHP crystallizes in the monoclinic space group C2/c with a = 26.105(3), b = 8.2250(10), c = 13.8750(10) Å, β = 116.02(1)°, V = 2677.2(5) Å3, and Z = 8. The 2,6-dimethylpyridinium (DPM) is held with the hydrogen phthalate ion (HPI) by intermolecular hydrogen bond of N-H-O. A noncentered hydrogen atom is involved in the short intramolecular hydrogen of O-O [2.398(2) Å] between the neighboring carboxylic groups. The phenyl ring of the HPI appears to be deformed in comparison with the original. The entity of HPI in itself and DMPMHP as a whole are arranged in a rumple pattern. The geometrical arrangement in the crystal structure is characterized by the formation of laminar ribbons of DPMHP.
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    The crystal structures of two reaction products of α-halopyruvamide with nitrogen and sulfur nucleophiles (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 109-113 
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    ISSN: 1572-8854
    Keywords: α-halopyruvamide derivatives ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Two compounds have been prepared during the investigation of the reactivity of α-halopyruvamides. The reaction products: 3-(4-chlorophenyl)imidazo[1,2-a]pyridine-2-carboxamide (1) and 7-carbamoyl-5-phenyl-2,3-dihydro[1,3]thiazolo[4,3-b][1,3]thiazol-4-ium chloride (2) were structurally characterized by x-ray crystallography. Compound 1 crystallizes in the orthorhombic space group Pca21 with a = 28.813(2), b = 9.369(1), and c = 9.361(1) Å. The structure contains two crystallographically different molecules. Compound 2 crystallizes in the monoclinic space group P21/c with the following cell parameters: a = 8.5895(8), b = 22.499(2), c = 7.4133(6) Å, and β = 110.204(1)°.
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    Synthesis and molecular structure of N-[3-(p-bromophenyl)-1,2,4-oxadiazol-5-yl]methylphthalimide. III. (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 131-134 
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    ISSN: 1572-8854
    Keywords: 1,2,4-Oxadiazole ; crystal structure ; phthalimide derivative ; AM1 method ; STO-3G basis set
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The synthesis, spectroscopic studies and crystal structure of the title compound is described. The crystallographic studies showed that the p-bromophenyl group is very nearly coplanar with the 1,2,4-oxadiazole ring. The nearly planar phthalimide group makes an angle of about 98° with the bromophenyloxadiazole plane. Semi-empirical (AM1) and ab initio (STO-3G, 6-31G) molecular orbital calculations have been carried out for this compound and a comparison of bond angles, bond lengths and torsion angles has been made with the experimental values, which are remarkably close to each other. This compound crystallizes in the monoclinic space group P21/c with a = 13.6299(2),b = 13.9836(2), c = 8.4817(2) Å, β = 101.9070(10)°, V = 1581.79(5) Å3, and Z = 4.
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    Crystal and molecular structure of augustamine (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 135-138 
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    ISSN: 1572-8854
    Keywords: alkaloid ; tazettine type ; amaryllidaceae ; crystal structure ; molecular mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of augustamine (1), C17H19NO4 an amaryllidaceae alkaloid of the tazettine group has been determined by direct methods from single crystal x-ray diffractometer data and refined by full-matrix least squares. The alkaloid (1) crystallizes in the space group P212121, with cell parameters: a = 7.833(8) b = 11.08(2) å, c = 16.69(6) Å, Z = 4, Dc = 1.381 g/cm−3, R = 7.6% for 1115 observed reflections. The molecule, having a hexacyclic ring system, is very rigid with the ring B in a chair conformation. Molecular mechanics calculations have been made using MM3(2000) force field.
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    Synthesis, crystal structure of a one-dimensional cobalt—azide complex through hydrogen bond (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 159-162 
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    ISSN: 1572-8854
    Keywords: crystal structure ; cobalt (II) complex ; one-dimensional chain ; hydrogen bond
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A one-dimensional chain complex, {[Co(bpm)2(N3)2][Co(bpm)2(H2O)2]} (ClO4)2, (bpm being bis(pyrazol-l-yl)methane), has been synthesized and characterized by X-ray diffraction: triclinic, space group P - 1 with a = 8.805(2) Å, b = 8.902(2) Å, c = 13.621(3) Å, α = 84.27(3)°, β = 84.63(3)°, γ = 80.05(3)°, V = 1043.2(4) Å3, Z = 1. Two cobalt atoms have ideal octahedral environments with different coordination atoms. One cobalt atom is six-coordinated with nitrogen atoms from two bpm ligands and two azide ligands, while the other cobalt atom is coordinated by four nitrogen atoms from bpm and two oxygen atoms from water molecules. The complex forms one-dimensional chain through hydrogen bonds.
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    Syntheses, characterization, and structural analyses of several f-block isothiocyanatonitrato complexes (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 301-309 
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    ISSN: 1572-8854
    Keywords: Synthesis ; crystal structure ; dioxouranium(VI) ; lanthanide(III) ; thiocyanate ; nitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Reactions of tetra-n-butylammonium thiocyanate with lanthanide and uranyl nitrates yield complexes of the general type [(Bu)4N]x[M(NCS)y(NO3)z]. Samples of [(Bu)4N]2 [UO2(NCS)3( NO3)] (1), [(Bu)4N]3[Yb(NCS)4(NO3)2] (2), and [(Bu)4N]3[Nd(NCS)4(NO3)2rsqb; (3) were prepared from alcohol solutions. Crystallization of 1 occurs in the centrosymmetric monoclinic space group C2/c (No. 15) with a = 17.949(4) Å, b = 16.587(3) Å, c = 16.763(3) Å; β = 99.77(3)°; and Z = 4. The seven-coordinate uranium(VI) ion exhibits a pentagonal bipyramid coordination environment. Crystallization of 2 occurs in the centrosymmetric orthorhombic space group Pnnn (No. 48) with a = 12.530(2) Å, b = 12.9440(10) Å, c = 21.203(2) Å; Z = 2. The eight-coordinate ytterbium(III) ion expresses a dodecahedral coordination environment. Crystallization of 3 occurs in the noncentrosymmetric monoclinic space group Cc (No. 9) with a = 16.556(2) Å, b = 18.130(2) Å, c = 23.984(4) Å; Z = 4. The 10-coordinate neodymium(III) ion exhibits a dodecahedral coordination environment. Characterization includes physical property determinations, conoscopic studies, IR spectroscopic identifications, and UV spectral data. Details of the syntheses along with selected bond distances and angles are presented and discussed.
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    A dimeric pervanadyl (VO2+) complex with a tridentate Schiff base ligand (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 329-333 
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    ISSN: 1572-8854
    Keywords: Pervanadyl complex ; Schiff base ; di(μ-oxo)-bridged dimer ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A di(μ-oxo)-bridged dinuclear complex, [VO2(pamh)]2 was isolated by reacting bis(acetylacetonato)vanadium(IV) and the Schiff base, N-(anisoyl)-N′-(picolinylidene)-hydrazine (Hpamh) in acetonitrile. The complex crystallizes in the space group $$P\bar 1 $$ ;1; (#2) on crystallographic inversion center. Crystal data: a = 8.2202(12) Å, b = 9.8389(19) Å, c = 10.1907(17) Å, α = 68.245(15)°, β = 74.47(2)°, γ = 66.710(19)°, V = 696.0(2) Å3, and Z = 1. The physical properties of the complex and the structural parameters are consistent with the +5 oxidation state of the metal ions. The monomeric VO2(pamh) unit is square-pyramidal. The planar mononegative ligand (pamh−) coordinates the metal ion via the pyridine-N, the imine-N, and the amide-O atoms. One of the oxo groups completes the NNOO basal plane and also participates in the Vndash;Ondash ;V bridge formation. The other oxo group satisfies the fifth apical coordination site. The molecular structure of the dimeric complex, [VO2(pamh)]2 can be described as two edge-shared distorted VO4N2 octahedra.
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    Crystal structure and spectroscopy of a hydrogen-bridged one-dimensional Cu(II) complex containing both octahedral and square pyramidal geometries in the same unit cell (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 351-357 
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    ISSN: 1572-8854
    Keywords: Helical hydrogen-bridged one-dimensional Cu(II) complex ; trans-4-styrylpyridine ; crystal structure ; IR and electronic spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Single crystals of the helical hydrogen-bridged one-dimensional Cu(II) complex, [Cu(stpy)2(CH3COO)2(H2O)2] (1) [Cu(stpy)2(CH3COO)2(H2O)] (2), are prepared and characterized by elemental and thermal analyses, IR, electronic and X-ray crystal structure determination. The crystals are monoclinic, of space group C2/c, with unit cell parameters a = 31.842(7) Å, b = 5.9829(10) Å, c = 30.970(14) Å, β = 111.78(3)°, Z = 4. The asymmetric unit contains two different types of Cu(II) polyhedra, namely, octahedron and square pyramid within the same unit cell. 1 has elongated octahedral geometry with two nitrogen atoms from stpy and two oxygen atoms from synmonodentate acetate ligands, transcoordinated to Cu(II) in the basal plane. The oxygen atoms of the two water molecules occupy the axial positions. 2 has Cu(II) coordination polyhedra similar to 1, except that only one of the apical positions is occupied by a water molecule. The structure consists of two independent linear chains, one involving octahedral (1) and the other involving square-pyramidal (2) polyhedra, held by hydrogen bridges. The Cu–Cu intra- and interchain separations in both 1 and 2 are 5.983 and 8.214 Å. The unit cell packing shows weak π-stacking between adjacent coordinated stpy ligands in the chain, resulting in ladder-type structure. Further, the extended packing reveals helical arrangement of Cu(II) polyhedra in the lattice.
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    Crystal structure of [Yb(L(NO3)2(H2O)2](NO3), L = bromo-N,N,N′,N′-tetraethylmalonamide (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 455-458 
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    ISSN: 1572-8854
    Keywords: Ytterbium ; malonamide ; crystal structure ; extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract [Yb(L(NO3)2(H2O)2](NO3), L = bromo-N,N,N′,N′-tetraethylmalonamide crystallizes in the triclinic spacegroup P-1 with cell dimensions a = 9.030(9), b = 12.036(12), c = 12.392(13) Å, α = 84.52(1), β = 77.58(1), γ = 67.21(1)° , dcalc = 1.935 g cm-3 for Z = 2. The ytterbium atom in the complex cation is nine-coordinate being bonded to two oxygen atoms from the malonamide ligand, two nitrate anions, and three water molecules.
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    N-Arylmaleimide derivatives (2000)
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    Journal of chemical crystallography 30 (2000), S. 563-571 
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    ISSN: 1572-8854
    Keywords: Maleimide ; crystal structure ; photopolymerization ; monomer ; conformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Nine phenyl substituted N-phenylmaleimide monomers for photopolymerization studies have been characterized by x-ray crystallography. Structures for N-(2′-t-butylphenyl)maleimide (1), P21/n, a = 10.197(3) Å, b = 11.904(4) Å, c = 10.496(5) Å, β = 100.61(3)° N-(2′-trifluoromethylphenyl)maleimide (2), P21/c, a = 11.763(8) Å, b = 10.699(9) Å, c = 8.284(5) Å, β = 90.02(5)° N-(2′,6′-diisopropylphenyl)maleimide hemibenzene solvate (3), Pc, a = 16.747(6) Å, b = 8.552(3) Å, c = 12.899(4) Å, β = 105.08(3)° N-(2′,6′-diisopropylphenyl) maleimide (unsolvated) (4), C2/c, a = 28.146(10) Å, b = 8.434(4) Å, c = 12.881(4) Å, β = 92.20(4)° N-(2′-bromo-3′,5′-bis(trifluoromethyl)phenyl) maleimide (5), P21/n, a = 8.7115(16) Å, b = 16.125(3) Å, c = 9.6707(19) Å, β = 99.757(15)° N-(2′-phenylphenyl)maleimide (6), P21/n, a = 8.519(4) Å, b = 13.742(5) Å, c = 11.147(4) Å, β = 92.25(3)° N-(4′-methoxyphenyl)maleimide (7), P21/n, a = 9.320(3) Å, b = 6.621(2) Å, c = 16.059(6) Å, β = 99.58(3)° N-(2′-trifluoromethylphenyl)-2-methylmaleimide (8), Fdd2, a = 43.362(12) Å, b = 8.202(2) Å, c = 12.720(4) Å and N-(2′-trifluoromethylphenyl)-2-methanosuccinimide (9), Cc, a = 7.708(2) Å, b = 22.191(9) Å, c = 7.137(2) Å, β = 115.76(2)° are described. Molecules with bulky 2′-substituents show larger rotations between the mean phenyl and maleimide ring planes, and varying degrees of distortion to the imide group.
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    Mechanism of the hydrodenitrogenation of o-toluidine and methylcyclohexylamine over NiMo/γ-Al2O3 (2000)
    Springer
    Topics in catalysis 11-12 (2000), S. 327-333 
    Details
    ISSN: 1572-9028
    Keywords: hydrodenitrogenation ; toluidine ; methylcyclohexylamine ; kinetics ; nickel-promoted molybdenum sulphide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hydrodenitrogenation (HDN) of o-toluidine and its reaction intermediates was studied over a NiMo/γ-Al2O3 catalyst. The kinetics of the HDN of methylcyclohexylamine and of the hydrogenation of cyclohexene were also studied. Hydrogenation of o-toluidine alone produces methylcyclohexene and methylcyclohexane. When a sufficient quantity of cyclohexene is added during the HDN of toluidine, methylcyclohexylamine, the first intermediate in the hydrogenation of toluidine, becomes detectable. Because of its strong adsorption constant and high rate constant for reacting further to methylcyclohexene and methylcyclohexane, methylcyclohexylamine is not observed in the HDN of toluidine. Adding cyclohexene decreases the adsorption of methylcyclohexylamine, thus enabling its detection. The rate and adsorption constants of methylcyclohexylamine and cyclohexene in the HDN of methylcyclohexylamine were calculated by fitting the kinetic data to a Langmuir–Hinshelwood equation. A two-site model was used to describe the surface reactions, with one site for the methylcyclohexylamine reactions and the other for the cyclohexene reaction.
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    Static and Kinetic Studies on the Adsorption Behavior of Sulfadiazene (2000)
    Springer
    Adsorption 6 (2000), S. 349-357 
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    ISSN: 1572-8757
    Keywords: sulfadiazene ; adsorption ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract To investigate the nature of interactive forces between sulfadiazene molecules and alumina surface the experiments were performed for the adsorption of sulfadiazene (SD) from its aqueous sulution onto the alumina surfaces at 25 ± 0.2°C and the influence of factors such as increasing concentration of SD (4.0–20.0 × 10−3 mol cm−3), the time required for adsorption equilibrium, pH (2.0–12.0) and temperature (5–45°C) of the adsorption medium, the presence of ions like Cl−, SO2− 4 and PO3− 4 (0.01–0.30 M) and organic solvents (5% v/v) were observed on the course of adsorption of SD. Various adsorption and kinetic parameters such as adsorption coefficient, the rate constants for adsorption and desorption were also evaluated. The results of the above cited studies facilitated to formulate the mechanisms of interaction between SD and alumina surfaces. From application view point the present work may be a potential tool for an effective chromatographic separation of sulfa drugs from industrial effluents.
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    NO reduction over La2O3 using methanol (2000)
    Springer
    Catalysis letters 64 (2000), S. 65-75 
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    ISSN: 1572-879X
    Keywords: NO reduction ; CH3OH ; La2O3 ; methyl nitrite ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Nitric oxide (NO) reduction by methanol was studied over La2O3 in the presence and absence of oxygen. In the absence of O2, CH3OH reduced NO to both N2O and N2, with selectivity to dinitrogen formation decreasing from around 85% at 623 K to 50–70% at 723 K. With 1% O2 in the feed, rates were 4–8 times higher, but the selectivity to N2 dropped from 50% at 623 K to 10% at 723 K. The specific activities with La2O3 for this reaction were higher than those for other reductants; for example, at 773 K with hydrogen a specific activity of 35 μmol NO/s m2 was obtained whereas that for methanol was 600 μmol NO/s m2. The Arrhenius plots were linear under differential reaction conditions, and the apparent activation energy was consistently near 14 kcal/mol with CH3OH. Linear partial pressure dependencies based on a power rate law were obtained and showed a near‐zero order in CH3OH and a near‐first order in H2. In the absence of O2, a Langmuir–Hinshelwood type model assuming a surface reaction between adsorbed CH3OH and adsorbed NO as the slow step satisfactorily fitted the data, and the model invoking two types of sites provided the best fit and gave thermodynamically consistent rate constants. In the presence of O2 a homogeneous gas‐phase reaction between O2, NO, and CH3OH occurred to yield methyl nitrite. This reaction converted more than 30% of the methanol at 300 K and continued to occur up to temperatures where methanol was fully oxidized. Quantitative kinetic studies of the heterogeneous reaction with O2 present were significantly complicated by this homogeneous reaction.
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    Oxidation of dicyclopentadiene catalyzed by palladium(II) acetate and p-benzoquinone in the presence of inorganic acid (2000)
    Springer
    Catalysis letters 69 (2000), S. 103-107 
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    ISSN: 1572-879X
    Keywords: dicyclopentadiene ; Wacker oxidation ; Pd(AcO)2 ; benzoquinone ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxidation of dicyclopentadiene catalyzed by palladium(II) acetate and benzoquinone in the presence of perchloric acid was studied. Tricyclodecenone in high selectivity (85–98%) at a conversion of dicyclopentadiene up to 76% was obtained. The kinetic model assumed the significant inhibition complexation between dicyclopentadiene and tricyclodecenone with the catalytic species.
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    Oxygen Configuration in the Superconductor (Hg0.7Mo0.3)Sr2(Ca1−xRx)Cu2Oz (R = Nd and Pr) (2000)
    Springer
    Journal of superconductivity 13 (2000), S. 111-119 
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    ISSN: 1572-9605
    Keywords: superconductivity ; Hg-based cuprate ; Hg-1212 (Hg,Mo)Sr2(Ca,R)Cu2O z ; neutron diffraction ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Two series of Hg-based oxides (Hg0.7Mo0.3)Sr2(Ca1−x R x )Cu2O z (R = Nd and Pr, 0.2 ≤ x ≤ 0.7) have been synthesized. Electrical-resistivity measurements show that these compounds are superconductors with maximum onset T c of 107 and 102 K for Nd- and Pr-containing samples, respectively. The neutron powder diffraction experiments on both as-prepared and O2-annealed samples of R = Nd revealed that the O(3) site at the HgOδ sheets are fully occupied and shifted towards the Hg/Mo site to form Mo–O bonds.
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    Kinetic Analysis of the Decomposition of Chelates of Di-alkyldithiocarbamate of Cd(II) (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 633-642 
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    ISSN: 1572-8943
    Keywords: cadmium ; dialkyldithiocarbamate ; kinetics ; thermal decomposition ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal decomposition kinetics of the solid complexes Cd(S2 CNR2 )2 , where R =C2 H5 , n -C3 H7 , n -C4 H9 or iso -C4 H9 , was studied by using isothermal and non-isothermal thermogravimetry. The superimposed TG/DTG/DSC curves revealed that thermal decomposition reactions occur in the liquid phase. The kinetic model that best fitted the experimental isothermal TG data was the one-dimensional phase-boundary reaction-controlled process R1 . The thermal analysis data suggested the thermal stability sequence Cd(S2 CNBun 2 )2 〉Cd(S2 CNPrn 2 )2 〉Cd(S2 CNBui 2 )2 〉Cd(S2 CNEt2 )2 , which accords with the sequence of stability of the apparent activation energies.
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    Kinetic and Thermodynamic Studies of Facial and Meridional uns-cis-[Co(eddp)gly] Complexes (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 807-814 
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    ISSN: 1572-8943
    Keywords: facial and meridional Co(III) complexes ; kinetics ; thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal properties of facial and meridional uns-cis-[Co(eddp)gly]0.5H2O complexes were investigated by means of DSC and TG techniques. It wasshown that the processes of thermal decomposition of these complexes are multi-stepdegradation processes, which can also be well separated into individual steps, depending onthe molecular symmetry. Thus, the process of thermal degradation of the meridional isomerof the above complex consists of 4 well-separated steps in the temperature interval from 100to 500°C. The corresponding kinetic and thermodynamic parameters of this process weredetermined, and a possible mechanism is discussed.
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    Thermal Decomposition Kinetics of Some Metal Complexes of N,N-diethyl-n '-benzoylthiourea (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 955-965 
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    ISSN: 1572-8943
    Keywords: kinetics ; metal complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermogravimetry (TG) and differential thermal analysis (DTA) were performed on the complexes with general formula (M(DEBT)n (where M =Fe, Co, Ni, Cu or Ru; n =2, or 3 and DEBT=N,N-diethyl-N'-benzoylthiourea). Derivative thermogravimetric (DTG) curves were also recorded in order to obtain decomposition data on the complexes. The complexes of Fe(III), Co(II), Ni(II), Cu(II) and Ru(III) displayed two- or three-stage decomposition patterns when heated in a dynamic nitrogen atmosphere. Mass loss considerations relating to the decomposition stages indicated the conversion of the complexes to the sulfides or to the corresponding metal alone (Cu, Ru, NiS, CoS or FeS). Mathematical analysis of the TG and DTG data showed that the order of reaction varied between 0.395 and 0.973. Kinetic parameters such as the decomposition energy, the entropy of activation and the pre-exponential factor are reported.
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    Fast Gas Adsorption Measurements For Complicated Adsorption Mechanisms (2000)
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    Journal of thermal analysis and calorimetry 62 (2000), S. 429-433 
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    ISSN: 1572-8943
    Keywords: adsorption ; fast measurement ; gravimetry ; kinetics ; sorption ; kw6
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Jäntti introduced a method to reduce the time required for the stepwise measurement of adsorption isotherms. After each pressure change he measured the adsorbed mass three times and calculated its equilibrium value at the new pressure. In the present paper, we discuss the applicability of this method in a broader scope without starting from a given combination of sorptive and adsorbent and the influence of measuring inaccuracies. The method is applied to detect whether the adsorption process is based on more than one adsorption mechanism or not.
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    Study of Thermal Decomposition Kinetics of Low-temperature Reaction of Ammonium Perchlorate by Isothermal TG (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 375-386 
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    ISSN: 1572-8943
    Keywords: activation energy ; ammonium perchlorate ; decompositon ; isothermal ; kinetics ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of the thermal decomposition of ammonium perchlorate at temperatures between 215 and 260°C is studied, in this work, by measuring the sample mass loss as a function of time applying the isothermal thermogravimetric method. From the maximum decomposition rate – temperature dependence two different decomposition stages, corresponding to two different structural phases of ammonium perchlorate, are identified. For the first region (215–235°C), corresponding to the orthorhombic phase, the mean value of the activation energy of 146.3 kJ mol–1, and the pre-exponential factor of 3.43⋅1014 min–1 are obtained, whereas for the second region (240–260°C), corresponding to the cubic phase, the mean value of the activation energy of153.3 kJ mol–1, and the pre-exponential factor of 4.11⋅1014 min–1 are obtained.
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    Theoretical and Experimental Investigations of The Decomposition of 10-methylacridinium Halides (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 35-43 
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    ISSN: 1572-8943
    Keywords: kinetics ; 10-methylacridinium halides ; thermodynamics ; thermogravimetric investigations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 10-Methylacridinium chloride, bromide and iodide were prepared in crystalline forms (the first two salts as monohydrates) and subjected to thermogravimetric investigations. Decomposition of the compounds is initially accompanied by the liberation of water (in case of monohydrates), halomethanes and acridine molecules. As decomposition proceeds, side reactions occur which are reflected in a complex pattern of thermogravimetric curves. TG traces corresponding to the initial decomposition stage were used to determine the kinetic characteristics of the thermal dissociation of the salts. MNDO/d, AM1 and PM3 methods were employed independently to examine reaction pathways and to predict thermodynamic and kinetic barriers for the thermal decomposition of the compounds. These data were subsequently supplemented with theoretically determined crystal lattice energies, which enabled the relevant characteristics for the decomposition of crystalline phases to be predicted. The theoretically predicted characteristics are qualitatively comparable with those originating from thermogravimetric investigations, which allows one to believe that both are valid.
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    Thermal Decomposition of Triazine Herbicides. I. 1,2-(4-chloro-6-ethylamino-1,3,5-triazin-2-ylamino)-2-methylpropionitrile (cyanazine) (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 103-110 
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    ISSN: 1572-8943
    Keywords: cyanazine ; DSC ; kinetics ; thermal stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cyanazine was taken as an example for investigations under the influence of different conditions on thermal decomposition of triazine herbicides. DSC measurements were carried out under atmospheric pressure and hermetically closed, under pressure 1.3 kPa. The influence of the pressure on the constant reaction rate of decomposition of cyanazine was discussed. It was also proved that the predicted reaction constant rates from isothermal and non-isothermal measurements are consistent.
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    Influence of Gas Atmosphere on Removal of Sulphate Groups From Titanium Oxide (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 247-255 
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    ISSN: 1572-8943
    Keywords: desulfuration ; gas atmosphere ; kinetics ; thermal decomposition ; titanium dioxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The studies were devoted to determination of the effect of gas atmosphere and its pressure on the second step of decomposition of hydrated titanium dioxide (HTD) promoted by sulfate groups. It has been found that thermal decomposition of HTD at temperatures above 300°C consists of a number of processes such as dehydroxylation, desulfuration, recrystallization and sintering of solid grains, photochemical processes (if the decomposition proceeds in the presence of light) and adsorption of gas phase components (in the presence of air or SO2). Kinetic parameters characterizing this step of decomposition have been determined for processes carried out in vacuum and in argon or air atmospheres (at a pressure of 13.33hPa). The kinetic curves of decomposition carried out in the presence of gases capable of being adsorbed on the surface of partly dehydrated HTD are featured by local extrema due to simultaneous processes of decomposition and adsorption of gas components.
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    Solid State Coordination Chemistry. The quantitative thermoanalytical study of thermal dissociation reactions (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 9-15 
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    ISSN: 1572-8943
    Keywords: coordination compounds ; kinetics ; thermal dissociation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Physicalo-chemical importance of the quantitative study of kineticliability of coordination compounds in thermal dissociation processes is considered. Muchattention is given to the proof of the physicalo-chemical meaning and validity of kineticparameters calculated from thermoanalytical data. Experimental data (thermal dissociation ofcoordination compounds and clathrates with such a matrix) are discussed.
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    The Effect of Cross-linked Polyethylene As a Surface Modifier on Crystallization of Polypropylene (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 401-407 
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    ISSN: 1572-8943
    Keywords: cross-linking ; isothermal crystallization ; kinetics ; modification ; polypropylene ; silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of addition of silica on the parameters of isothermal crystallization of polypropylene has been investigated. It was found that the covering of the silica surface by a layer of low-density polyethylene leads to a deactivation of the filler regarding the positive effect on the polypropylene crystallization rate parameters. Cross-linking of the surface polyethylene layer results in a stronger attachment of the modifying polymer to the filler surface and the deactivation effect of the silica surface modification is more pronounced.
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    Formation of Cr(II) Species in the H2/CrO3 System. Parameter control (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 541-547 
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    ISSN: 1572-8943
    Keywords: Cr(II) ; chromium trioxide ; kinetics ; reduction ; thermal analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal behaviour of CrO3 on heating up to 600°C in dynamic atmospheres of air, N2 and H2 was examined by thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy and diffuse reflectance spectroscopy (DRS). The results revealed three major thermal events, depending to different extents on the surrounding atmosphere: (i) melting of CrO3 near 215°C (independent of the atmosphere), (ii) decomposition into Cr2(CrO4)3 at 340–360°C (insignificantly dependent), and (iii) decomposition of the chromate into Cr2O3 at 415–490°C (significantly dependent). The decomposition CrO3 → Cr2(CrO4)3 is largely thermal and involves exothermic deoxygenation and polymerization reactions, whereas the decomposition Cr2(CrO4)3 → Cr2O3 involves endothermic reductive deoxygenation reactions in air (or N2) which are greatly accelerated and rendered exothermic in the presence of H2. TG measurements as a function of heating rate (2–50°C min−1) demonstrated the acceleratory role of H2, which extended to the formation of Cr(II) species. This could sustain a mechanism whereby H2 molecules are considered to chemisorb dissociatively, and then spillover to induce the reduction. DTA measurements as a function of the heating rate (2–50°C min−1) helped in the derivation of non-isothermal kinetic parameters strongly supportive of the mechanism envisaged.
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    Evaluation of Kinetic Data for Crystallization of Tio2 Prepared by Hydrolysis Method (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 595-604 
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    ISSN: 1572-8943
    Keywords: crystal structure ; DSC ; oxides ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The formation of TiO2 prepared by hydrolysis method was presented. Thermodynamics and kinetics of anatase crystallization reaction were investigated. Differential method of kinetic data evaluation in non-isothermal conditions according toKissinger, Ozawa and Kazeev-Yerofeev was applied. Starting, crystallized and thermally treated powders were determined using X-ray powder diffraction analysis. The characteristic parameters (the activation energy, constant rate and formal kinetic order of reaction) of TiO2 formation were calculated using DSC data.
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    Kinetic Modeling of Advanced Inorganic Glass-ceramics Formation by Crystal Growth From Pre-existing Nuclei (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 667-674 
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    ISSN: 1572-8943
    Keywords: accommodation function ; crystal growth ; glass-ceramics ; kinetics ; number of nuclei ; thermal history
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Kinetic modeling of the crystal growth from pre-existing nuclei was reexamined to obtain a fundamental information about the controlled crystallization of glasses during formation of advanced inorganic glass-ceramics. Methods of kinetic analysis were reviewed by taking account of thermal history of the sample within the temperature range of nucleation. An accommodation function depending on the thermal history was introduced in the kinetic equation. The role of the accommodation function was reinvestigated when determining the activation energy from a series of kinetic curves. The kinetic description of the crystal growth in the samples with different thermal history was generalized by extrapolating the rate behavior to infinite temperature.
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    Temperature Modulated DSC. Theoretical interpretation (2000)
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    Journal of thermal analysis and calorimetry 60 (2000), S. 333-343 
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    ISSN: 1572-8943
    Keywords: base line ; DSC ; kinetics ; modeling ; thermodynamics ; TMDSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The application of non-linear heating program to a heat-flux DSC apparatus has attracted much attention. From thermodynamics viewpoint, it is shown that the variation of enthalpy of a sample changing with temperature change is due, to both the true heat capacity of the sample and the enthalpy of some transformations occurring in the sample, characterized by its degree of advance. Using the simple assumption that the rate of the transformation is proportional to the distance from the thermodynamic equilibrium, an electrical model of the thermal event is given. Using the coupled cell model of the DSC apparatus, we show how to obtain the rate of transformation of the sample and heat capacity, which is directly related to the base line of the experiment.
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    Practical Thermogravimetry (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 759-778 
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    ISSN: 1572-8943
    Keywords: decomposition temperature ; error sources ; gas-flow and vapor control ; kinetics ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The well-known divergence between the present ‘state of the art’ of thermogravimetry and industrial requirements is discussed. Sources of errors are analyzed and the optimization of measuring conditions is discussed regarding the problems associated with static and dynamic (flow) atmospheres, and interactions between materials and gases or vapors. Recommendations for gas-flow control systems and vapor sources are given. Thermal stability and the kinetics of gas-evolving, reversible, thermal decompositions of solids are discussed. The scope of TG-derived kinetics for practical use is examined. Some new characteristic points of TG curves are proposed and defined, e.g. ‘procedure-independent decomposition temperature’ and ‘augmented decomposition temperature’ (obtained at pseudo-equilibrium conditions).
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    The Thermodynamic Driving Force in the Kinetic Evaluation of Thermoanalytical Curves (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 879-886 
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    ISSN: 1572-8943
    Keywords: driving force ; kinetics ; rate equation ; reversible reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper outlines the different ways of taking the distance from thermodynamic equilibrium into account in kinetic studies based on thermoanalytical experiments. The three main approaches are: (i) avoiding or neglecting the effect of the reverse reaction, (ii) describing the influence of distance from equilibrium on apparent kinetic parameters, and (iii) incorporating a driving force factor in the rate equation. Finally, the contradiction of the microscopic nature of the processes and the macroscopic character of the usual rate equation are briefly discussed.
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    Kinetic Analysis of the Thermal Decomposition of Synthetic Malachite by CRTA (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 943-954 
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    ISSN: 1572-8943
    Keywords: CRTA ; kinetics ; self-generated atmospheric conditions ; synthetic malachite ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetic behavior of the thermal decomposition of synthetic malachite was investigated by means of CRTA under different conditions of reduced pressure, flowing gases and quasi-isobaric atmospheres. The thermal decomposition was found to proceed at lower temperatures under the influence of the self-generated gases, CO2 and H2O. From a viewpoint of chemical equilibrium, the normal and opposite effects on the overall kinetics were observed for the self-generated CO2 and H2O, respectively. The complexity of the present reaction is also reflected by the variations of the apparent kinetic parameters which depend on the applied and self-generated atmospheric conditions. The practical usefulness of CRTA when applied to a complicated thermal decomposition is discussed as exemplified by the kinetic approaches to the present reaction.
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    Thermal Studies on Some Lanthanide Complexes (2000)
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    Journal of thermal analysis and calorimetry 61 (2000), S. 151-156 
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    ISSN: 1572-8943
    Keywords: complexes ; kinetics ; TG-DTA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal behaviour of a few lanthanide complexes of the type ML3(I) [M=Eu,Gd; HL=4,4,4-trifluoro- 1-(2-napthyl)-1,3-butanedione and EuL30.5dmm dmm=2,6-dimethylmorpholine(II)], has been investigated. From thermogravimetric(TG) curves, the decomposition pattern of the compounds has been analysed on the basis of mass loss data. The order and activation energy of the thermal decomposition reactions have been elucidated. From differential thermal analysis (DTA) studies, the heat of reaction and rate of thermal decomposition reaction have been enumerated.
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    Non-isothermal Kinetic Study of the Heterogeneous Thermal Decomposition of a Mannich Compound (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 239-242 
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    ISSN: 1572-8943
    Keywords: kinetics ; Mannich compounds ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The authors present data concerning the evaluation of kinetic parameters of the decomposition of a Mannich compound by using the classical method of constant heating rate thermal analysis and the new one of controlled rate thermal analysis (CRTA). The data processed using the CRTA method allow to obtain more reliable kinetic parameters according to the proposed reaction mechanism.
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    URL: http://dx.doi.org/10.1023/A:1010197632277
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    Polypropylene Crystallization in an Ethylene-propylene-diene Rubber Matrix (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 437-450 
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    ISSN: 1572-8943
    Keywords: crystallization ; EPDM ; kinetics ; morphology ; PP ; rubber
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of the incorporation of an amorphous immiscible polymer (ethylene-propylene-diene- terpolymer) on the PP crystallization kinetics and thermodynamics is investigated by thermal analysis. The results of the investigation have shown that EPDM acts as a nucleant agent. A marked decrease of the half time of PP crystallization, τ1/2 , as well as a sensible increase of the overall crystallization rate, K n , has been observed in the presence of EPDM. Moreover, at any crystallization temperature, a minimum of τ1/2 , is obtained at 25% EPDM content in the blend. The Avrami model has been successfully applied to describe the crystallization kinetics of the blend. The kinetic curves obtained under non-isothermal conditions confirm the results obtained under isothermal conditions and demonstrate the nucleant action of the EPDM phase on the PP crystallization.
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    URL: http://dx.doi.org/10.1023/A:1010165317028
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    TG and DTA Study of the Thermal Dehydration of Metal-exchanged Zeolite-4A Samples (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 721-727 
    Details
    ISSN: 1572-8943
    Keywords: kinetics ; metal exchange ; thermaldehydration ; zeolite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zeolite-4A is a hydrated aluminosilicate which becomes more hydrated when exchanged with transition metals. In this work, the dehydration kinetics of cobalt, nickel and copper(II)-exchanged zeolite-4A were studied by means of TG and DTA over the temperature range from 20 to 500°C, and the numbers of water molecules in the metal-exchanged zeolite samples were calculated. It was observed that, as the ionic radius of the hydrated metal increased, the number of water molecules also increased. The loss of water from the zeolite samples generally occurred in the temperature range 100–300°C and was manifested in the DTA graphs by an extended endothermic effect. The DTA curves demonstrated that the peak position shifted towards lower temperatures as the metal concentration increased or, in other words, the water of hydration increased. The kinetic parameters (order of reaction and activation energy) were calculated via the Coats and Redfern method. The process of dehydration was found to follow first-order kinetics.
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    Kinetic Equations for Thermal Dissociation Processes. Part I. KEKAM equation (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 359-374 
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    ISSN: 1572-8943
    Keywords: KEKAM equation ; kinetics ; thermal dissociation of solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Relationships have been established between the average conversion degree and the dissociation time for polydisperse granular material, taking its grain size distribution into account. It has been checked in which cases the kinetic curves obtained by a numerical solution can be described in terms of KEKAM equation.
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    Critical Analysis of the Isoconversional Methods for Evaluating the Activation Energy. II. The activation energy obtained from isothermal data corresponding to two successive reactions (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 465-469 
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    ISSN: 1572-8943
    Keywords: isoconversional methods ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An analysis is presented of the consequences of the use of a one term equation containing apparent activation parameters, instead of the true rate equation to describe two successive decomposition reactions undergone by a solid compound. It is demonstrated that the apparent activation energy, obtained by means of isoconversional differential and integral methods, varies with the conversion degree for a relatively narrow temperature range and with temperature at a given value of the conversion degree. The activation energy values obtained with the isoconversional differential method are higher than the corresponding values obtained with the isoconversional integral method.
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    Kinetics of Thermal Decomposition of Plumbo-jarosite (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 869-875 
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    ISSN: 1572-8943
    Keywords: decomposition ; kinetics ; plumbo-jarosite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An investigation was carried out on the kinetics of thermal decomposition of plumbo-jarosite. The kinetic models of dissociation of the compounds in the ore were identified. The results of the kinetic studies and the mechanism of the process are discussed. The thermal decomposition of plumbo-jarosite occurs in three stages: the first up to 763, the second up to 1023 and the third up to 1223 K, the corresponding activation energy values being 62.2, 60.3 and 98.0 kJ mol–1 , respectively.
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    Thermal Characterization of Passivated Nanometer Size Aluminium Powders (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 805-818 
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    ISSN: 1572-8943
    Keywords: aluminium ; ARC ; DSC ; kinetics ; nanometric size ; SDT ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal properties of Alex, a nanosized Al powder, were determined using various techniques, including DSC, TG, simultaneous TG-DTA (SDT) and accelerating rate calorimetry (ARC). The results demonstrate that the specific heat capacities of nano and micron size Al powders are similar between 30 and 400°C. Dynamic and isothermal methods were used to determine the kinetic parameters for the oxidation reaction of Alex, which was detected at an onset temperature of 481°C. The results obtained were in good agreement with each other. From the ARC experiments, exotherms were detected near 340 and 260°C for experiments started at ambient pressure and at 0.72 MPa, respectively.
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    Thermal and Spectroscopic Studies on the Decomposition of Some Aminoguanidine Nitrates (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 861-871 
    Details
    ISSN: 1572-8943
    Keywords: DAGN ; kinetics ; mechanism and IR spectroscopy ; TAGN ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Diaminoguanidine nitrate (DAGN) and triaminoguanidine nitrate (TAGN),potential energetic materials in emerging propulsion technology with high mass impetus at low isochoric flame temperature have been studied as regards kinetics and mechanism of thermal decomposition using thermogravimetry (TG), differential thermal analysis (DTA),infrared spectroscopy (IR) and hot stage microscopy. Kinetics of thermolysis has been followed by isothermal TG and IR. For the initial stage of thermolysis of DAGN the best linearity with a correlation coefficient of 0.9976 was obtained for the Avrami-Erofe'evequation, n=2, by isothermal TG. The activation energy was found to be 130 kJ mol–1 and logA=11.4. The initial stage of thermolysis of TAGN also obeyed the Avrami-Erofe'ev equation, n=2, with a correlation coefficient of 0.9975by isothermal TG and the kinetic parameters are E=160.0 kJ mol–1 and logA=16.0. High temperature IR spectra showed exquisite preferential loss in intensity of the NH2, NH, N–N stretching and CNN bending. Spectroscopic and other results favour deamination reaction involving the rupture of the N–N bond as the primary step in the thermal decomposition.
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    URL: http://dx.doi.org/10.1023/A:1010113707251
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    Fractal Approach in the Kinetics of Solid-Gas Decompositions. Part II (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 979-984 
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    ISSN: 1572-8943
    Keywords: kinetics ; nucleation-growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The author presents some applications of the fractal geometry in the kinetics of heterogeneous decomposition of solids.
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    Study of The Mechanism and Kinetic Parameters of The Thermal Decomposition of Cobalt Sulphate Hexahydrate (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 935-942 
    Details
    ISSN: 1572-8943
    Keywords: CoSO46H2O ; kinetics ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermogravimetry (TG-DTG), and differential thermal analysis (DTA) were used in the study of the kinetics of decomposition of cobalt sulphate hexahydrate under an air atmosphere. The kinetics of the particular stages of CoSO4 6H2 O decomposition were evaluated from the dynamic mass loss data. The values of the kinetic parameters for each stage of the thermal decomposition were calculated from the α(T) data by using the integral method, applying the Coats-Redfern approximation.
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    Kinetic Study of the Accelerating Effect of Coal-burning Additives on the Combustion of Graphite (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 681-685 
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    ISSN: 1572-8943
    Keywords: coal-burning additive ; combustion ; graphite ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The catalytic and accelerating effects of three coal-burning additives (CBA) on the burning of graphite were studied with the help of thermogravimetric (TG) analysis. The kinetic study on the catalytic oxidation of the graphite doped with CBA was carried out and the results were presented. The results show that the CBA can change the carbon oxidation/combustion course by catalytic action and change the activation energy, thus improving the combustion efficiency.
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    Critical Analysis of the Isoconversional Methods for Evaluating the Activation Energy. I. Theoretical background (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 457-463 
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    ISSN: 1572-8943
    Keywords: isoconversional methods ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It is demonstrated that, if the activation energy depends on the degree of conversion, its values obtained by isoconversional differential and integral methods are different.
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    Modeling of the Phase Transformation Induced by Ball Milling in Anatase TiO2 (2000)
    Springer
    Journal of materials synthesis and processing 8 (2000), S. 139-144 
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    ISSN: 1573-4870
    Keywords: TiO2 ; phase transformations ; mechanical alloying ; kinetics ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A high-pressure and high-temperature phase of TiO2 : TiO2 II is formed transiently during room-temperature high-energy ball milling of anatase TiO2 : TiO2 anatase → TiO2 II → TiO2 rutile. Rutile is the only phase present after prolonged ball milling. The present paper focuses on the influences of physical and chemical processing conditions on the transformation kinetics. The effects of two milling parameters on the kinetics of phase transformation of anatase TiO2 were investigated: the nature of milling tools and the powder-to-ball weight ratio R. Granulometric characterizations and TEM observations have demonstrated that the transformation of TiO2 anatase into TiO2 II occurs without fracturing of particles and that TiO2 II nanograins form at the surface of anatase particles. The parameter R affects only the transformation rate. For a given R, the transformation rate is the largest with alumina grinding tools, intermediate with zirconia tools, and the smallest with steel tools. The parameters involved in current models of the mechanical alloying process do not suffice to explain the differences in transformation rates observed here. A parameter, which takes into account the influence of the mechanical properties of grinding materials, is considered.
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    URL: http://dx.doi.org/10.1023/A:1011351807629
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    Relating Single-Impact Events to Macrokinetic Features in Mechanical Alloying Processes (2000)
    Springer
    Journal of materials synthesis and processing 8 (2000), S. 271-277 
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    ISSN: 1573-4870
    Keywords: Comminution ; kinetics ; mechanical alloying ; phase transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract It has been shown that structural evolution occurring in powder mixtures subjected to mechanical treatment by milling follow well-defined conversion trends as a function of milling time. Sigmoidal curves were observed in the case of the mechanical alloying of transition metal mixtures, whereas a simpler kinetic course with a progressively decreasing transformation rate was found to characterize the disordering process of intermetallic equilibrium compounds by mechanical milling. Under the stipulation that collisions are the dominant energy transfer events, a kinetic model is developed to relate the observed macrokinetic features to the discrete powder fractions, which transform at each impact. Because of its intrinsic qualities, the milling process was regarded as discrete processing. A statistical approach was followed to work out a set of differential equations, solutions of which provide a sound description of the transformation kinetics in terms of conventional rate expressions. The model allows one to reproduce the different kinetic behaviors by means of a single, unifying mathematical formalism. Furthermore, quantifying the structural evolution rate by suitable kinetic constants permits the exploration of the reactive behavior of a system treated under different milling regimes or to compare, on an absolute basis, different systems processed under similar conditions.
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    High-Temperature Oxidation Behavior of the Co-Base Superalloy DZ40M in Air (2000)
    Springer
    Oxidation of metals 53 (2000), S. 351-360 
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    ISSN: 1573-4889
    Keywords: Co-base superalloy ; high-temperature oxidation ; kinetics ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of the Co-base superalloy DZ40M was studied in air at900–1100°C for times of up to 2000 hr. The results indicated thatthis alloy can grow a protective oxide scale at 900 and 1000°C duringisothermal oxidation, but not at 1100°C because of serious cracking andspalling of the oxide scales. Moreover, an internal-precipitate zone formedin the subsurface region of the alloy at all temperatures and times. Theprecipitates were rich in Cr in the vicinity of the alloy–scaleinterface and rich in Al deep in the alloy. The internal-precipitatemorphology changed from a granular to needlelike shape with increasingoxidation temperature.
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    Analysis of Aluminum—Yeast Hexokinase Interaction: Modifications on Protein Structure and Functionality (2000)
    Springer
    The protein journal 19 (2000), S. 199-208 
    Details
    ISSN: 1573-4943
    Keywords: Aluminum ; yeast hexokinase ; preferential interactions ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The aluminum and yeast hexokinase interaction was studied. Structural changes were correlated with variations in protein functionality. Results show two different behaviors: At low metal concentrations preferential adsorption of metal (and water exclusion) induces aggregate formation. No significant changes in the protein structure occur, but there is a continuous loss of activity (from the first concentration). At large salt concentrations a monomerization process and a conformational change in the secondary structure as well as in the three-dimensional structure take place. This change reduces the percentage of α-helix conformation, gives thermal stability to the protein, and allows the exposure of some tryptophan residue and hydrophobic regions. The protein inhibition increases. Conformational change and monomerization may allow access of the metal to the substrate site, mainly the ATP site. The inhibition in any case is of mixed type with a competitive component.
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    A Comparative Study of Human Muscle and Brain Creatine Kinases Expressed in Escherichia coli (2000)
    Springer
    The protein journal 19 (2000), S. 59-66 
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    ISSN: 1573-4943
    Keywords: Creatine kinase ; human ; expression ; brain ; muscle ; purification ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We report the expression of the human muscle (CK-MM) and brain (CK-BB) creatine kinases in Escherichia coli. The proteins have been purified to apparent homogeneity and several of their physical and kinetic properties investigated. In the process, we have conclusively verified the correct DNA sequence of the genes encoding the respective isozymes, and determined the correct primary structure and mass of the gene products. Alignment of the primary sequences of these two enzymes shows 81% sequence identity with each other, and no obvious gross structural differences. However, Western blot analyses demonstrated the general lack of antigenic cross-reactivity between these isozymes. Preliminary kinetic analyses show the K m and k cat values for the creatine and MgATP substrates are similar to values reported for other isozymes from various tissues and organisms. The human muscle and brain CKs do not, however, exhibit the synergism of substrate binding that is observed, for example, in rabbit muscle creatine kinase.
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    Stabilization of ammonium dinitramide in the liquid phase (2000)
    Springer
    Russian chemical bulletin 49 (2000), S. 1974-1976 
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    ISSN: 1573-9171
    Keywords: ammonium dinitramide ; thermal decomposition ; kinetics ; stabilization ; isotope composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of accumulation of the main products of thermal decomposition of ammonium dinitramide in the melt was investigated. The isotope composition of nitrogen-containing gases evolved by the decomposition of 15NH4N(NO2)2 and NH4 15N(NO2)2 was found. Easily oxidized salts, amines, amides, iodides, and other compounds soluble in the melt interfere with the liquid-phase decomposition of ammonium dinitramide.
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    The kinetics and mechanism of cyclodimerization of alkylthiopropenals (2000)
    Springer
    Russian chemical bulletin 49 (2000), S. 1977-1980 
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    ISSN: 1573-9171
    Keywords: 2-alkylthiopropenals ; Diels–Alder reaction ; kinetics ; reaction mechanism ; 2,5-dialkylthio-3,4-dihydro-2H-pyran-2-carbaldehyde ; IR spectroscopy ; ab initio calculations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of 2-alkylthiopropenals cyclodimerization was studied in the temperature range from -7 to +42 °C in heptane and at 20 °C in various solvents. The rate constants for cyclodimerization of 2-alkylthiopropenals are four orders of magnitude higher than those for dimerization of the oxygen-containing analogs, 2-alkoxypropenals, and are independent of the solvent polarity and substituent steric constant. The activation parameters for 2-butylthiopropenal cyclodimerization were estimated. The distribution of electron density in the 2-methoxy- and 2-methylthiopropenals molecules was calculated by the ab initio method. From comparison of the HOMO and LUMO energies for these aldehydes it was concluded that the ratio between the cyclodimerization rates for 2-alkylthio-, 2-ethoxypropenals, and propenal is determined by the HOMO–LUMO gap.
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    Cooperative Interactions in Photosensitized Modification of DNA with Oligonucleotide-derived Binary Reagents (2000)
    Springer
    Molecular biology 34 (2000), S. 814-822 
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    ISSN: 1608-3245
    Keywords: DNA ; kinetics ; oligonucleotide derivatives ; photomodification ; sensitization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Quantitative characteristics of thermodynamic and kinetic cooperativity arising in the process of photomodification of a single-stranded DNA fragment with binary systems of oligonucleotide conjugates forming an active site on the target were studied. Oligonucleotides of the binary system were complementary to adjacent segments of the DNA target, and contained arylazide (X) and perylene (S) residues covalently attached to their terminal phosphates. Upon irradiation at the perylene absorption wavelength, the target was modified by the arylazide residue, which was activated owing to the contiguity with the sensitizing perylene group in the tandem complex. Basing on the kinetic data, the constants of association of both derivatives of oligonucleotides with the target were determined: K x = 1.13 · 106 M–1, K s = 1.49 · 104 M–1. It was determined that association of both oligonucleotides with the target proceeded with a positive cooperativity characterized by parameter α = 45. The kinetic cooperativity parameter β was found to be approximately equal to 200; this characterized the acceleration of target modification in complex with the binary reagent versus that in the absence of sensitizer.
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    Functional Properties of Lactate Dehydrogenase from Dunaliella salina and Its Role in Glycerol Synthesis (2000)
    Springer
    Russian journal of plant physiology 47 (2000), S. 761-771 
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    ISSN: 1608-3407
    Keywords: Dunaliella salina ; lactate dehydrogenase ; kinetics ; glycerol synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The dependence of the catalytic properties of lactate dehydrogenase (LDH, EC 1.1.1.27) from a halophilic alga Dunaliella salina, a glycophilic alga Chlamydomonas reinhardtii, and from porcine muscle on glycerol concentration, medium pH, and temperature was investigated. Several chemical properties of the enzyme from D. salina differentiated it from the LDH preparation obtained from C. reinhardtii and any homologous enzymes of plant, animal, and bacterial origin. (1) V max of pyruvate reduction manifested low sensitivity to the major intracellular osmolyte, glycerol. (2) The affinity of LDH for its coenzyme NADH dropped in the physiological pH region of 6–8. Above pH 8, NADH virtually did not bind to LDH, while the enzyme affinity for pyruvate did not change considerably. (3) The enzyme thermostability was extremely low: LDH was completely inactivated at room temperature within 30 min. The optimum temperature for pyruvate reduction (32°C) was considerably lower than with the enzyme preparations from C. reinhardtii (52°C) and porcine muscle (61°C). (4) NADH greatly stabilized LDH: the ratio of LDH inactivation constants in the absence of the coenzyme and after NADH addition at the optimum temperature in the preparation from D. salina exceeded the corresponding indices of LDH preparations from C. reinhardtii twelve times and from porcine muscle eight times. The authors believe that these LDH properties match the specific metabolism of D. salina which is set at rapid glycerol synthesis under hyperosmotic stress conditions. The increase of cytoplasmic pH value produced in D. salina by the hyperosmotic shock can switch off the terminal reaction of the glycolytic pathway and thus provide for the most efficient utilization of NADH in the cycle of glycerol synthesis. As LDH is destabilized in the absence of NADH, this reaction is also switched off. In the course of alga adaptation to the hyperosmotic shock, glycerol accumulation and the neutralization of intracellular pH stabilize LDH, thus creating the conditions for restoring the complete glycolytic cycle.
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    Kinetic study of a thermostable β-glycosidase of Thermus thermophilus. Effects of temperature and glucose on hydrolysis and transglycosylation reactions (2000)
    Springer
    Glycoconjugate journal 17 (2000), S. 377-383 
    Details
    ISSN: 1573-4986
    Keywords: β-glycosidase ; temperature dependence ; kinetics ; glucose ; transglycosylation ; (Thermus thermophilus)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A β-glycosidase of a thermophile, Thermus thermophilus, belonging to the glycoside hydrolase family 1, was cloned and overexpressed in Escherichia coli. The purified enzyme (Ttβgly) has a broad substrate specificity towards β-D-glucoside, β-D-galactoside and β-D-fucoside derivatives. The thermostability of Ttβgly was exploited to study its kinetic properties within the range 25–80[emsp4 ]°C. Whatever the temperature, except around 60[emsp4 ]°C, the enzyme displayed non-Michaelian kinetic behavior. Ttβgly was inhibited by high concentrations of substrate below 60[emsp4 ]°C and was activated by high concentrations of substrate above 60[emsp4 ]°C. The apparent kinetic parameters (k cat and K m ) were calculated at different temperatures. Both k cat and K m increased with an increase in temperature, but up to 75[emsp4 ]°C the values of k cat increased much more rapidly than the values of K m . The observed kinetics might be due to a combination of factors including inhibition by excess substrate and stimulation due to transglycosylation reactions. Our results show that the substrate could act not only as a glycosyl donor but also as a glycosyl acceptor. In addition, when the glucose was added to reaction mixtures, inhibition or activation was observed depending on both substrate concentration and temperature. A reaction model is proposed to explain the kinetic behavior of Ttβgly. The scheme integrates the inhibition observed at high concentrations of substrate and the activation due to transglycosylation reactions implicating the existence of a transfer subsite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007104030314
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  • 98
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    Electronic Resource
    Tosyiate of ethyl 3-amino-2-phenyliodoniocrotonate: Synthesis, crystal structure, and synthesis of heterocyclic compounds based on it (2000)
    Springer
    Chemistry of heterocyclic compounds 36 (2000), S. 672-678 
    Details
    ISSN: 1573-8353
    Keywords: aminocrotonate ester ; pyridinium salts ; phenyliodonium salts ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ethyl 3-aminocrotonate, when reacted with hydroxy(tosyloxy)iodobenzene, forms the tosylate of ethyl 3-amino-2-phenyliodoniocrotonate which crystallizes well in up to 80% yield. X-ray analysis confirms the structure of the phenyliodonium salt, revealing intramolecular and unusual intermolecular hydrogen bonds, stabilizing the compound in the crystalline state. Reaction with pyridine, its 4-substituted derivatives, and 4,4′-bipyridine yields tosylates of 2-pyridinio-substituted ethyl 3-aminocrotonates.1H NMR and IR spectra support formation of an intramolecular hydrogen bond for the E-isomer, and iodonium salts in the case of pyridinium salts for the Z-isomer. The UV spectra of the pyridinium salts show an intramolecular charge transfer band.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02297675
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  • 99
    Electronic Resource
    Electronic Resource
    Statistical Properties of Stimulated Raman Scattering in a Nonlinear Regime (2000)
    Springer
    Journal of applied spectroscopy 67 (2000), S. 981-989 
    Details
    ISSN: 1573-8647
    Keywords: nonlinear regime of stimulated Raman scattering ; fluctuation ; Stokes radiation ; kinetics ; spectrum ; distribution function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Statistical properties of the Raman scattering of an intense step pulse are investigated by numerical solution of the equations of a semi-classical theory with assignment of a random Gaussian distribution of the initial polarization over the sample. The probability density functions of the intensity, energy, delay time, and width of a Stokes pulse and also of the position, height, and width of the spectral peaks of the first incidental Stokes component with the preservation of the phase memory of scattering centers are calculated. The influence of collisional dephasing on the fluctuation of these characteristics is considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004120404710
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  • 100
    Electronic Resource
    Electronic Resource
    Effect of Compaction Scheme on Property Distribution for Cumulative Charge Facings Formed from a Heterogeneous Powder Composite (2000)
    Springer
    Powder metallurgy and metal ceramics 39 (2000), S. 540-544 
    Details
    ISSN: 1573-9066
    Keywords: compaction ; facing ; cumulative charge ; powder ; composite ; heterogeneous structure ; particle ; kinetics ; surface ; die ; model ; xeroradiogram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental and numerical (finite element method) study is carried out for the effect of forming scheme on property distribution for cumulative charge facings made from composite heterogeneous powder material. An experimental procedure is developed for studying powder particle flow kinetics. It is shown that use of composite punches and partition of the moulded material into a number of sub-divisions with their successive compaction achieves a more uniform density distribution for an article. It is demonstrated how the direction of the force of friction on the die walls during compaction affects the compaction of articles with faces that are not perpendicular to the direction of the pressing. The results obtained make it possible to select the optimum compaction regime taking account of production features connected with powder material composition as well as service characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011359626701
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