Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1995-1999  (1,584)
  • 1920-1924
  • 1998  (696)
  • 1997  (888)
  • Theoretical, Physical and Computational Chemistry  (1,282)
  • Life Sciences (general)
  • crystal structure
Source
Material
Years
  • 1995-1999  (1,584)
  • 1920-1924
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Structure of a 1:1 complex between the anthelmintic drug mebendazole and propionic acid (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 11-15 
    Details
    ISSN: 1572-8854
    Keywords: Mebendazole–propionic acid complex ; molecular complex ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Recrystallization of the anthelmintic drug mebendazole from propionic acid yields a 1:1 molecular complex which crystallizes in the triclinic system space group $${P\bar 1}$$ , a = 5.928(2), b = 11.066(2), c = 14.337(6)Å, α = 94.89(3), β = 101.56(3), γ = 96.18(2)°, and Z = 2 complex units in the unit cell. An x-ray diffraction study revealed an R 2 2 (8) hydrogen bonding system in the complex, involving the unprotonated imidazole N and amide N–H function of the drug and the acid carboxylic group. Complex molecules form centrosymmetric dimers by intermolecular N–H···O hydrogen bonding involving the protonated imidazole N atom and the benzoyl O atom of the drug molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021766300133
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Crystal structure and EPR spectra of glycilglycilglycinocopper(II)bromide sesquihydrate (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 61-68 
    Details
    ISSN: 1572-8854
    Keywords: Cu(II) complex ; crystal structure ; EPR spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound, Cu(glyglygly)Br·1·5H2O, crystallizes in the space group C2/c, with a = 21.468(7), b = 6.716(5), c = 16.166(6) Å, β = 98.39°, and Z = 8. The tripeptide is bonded to one Cu(II) ion through the nitrogen [Cu–N=1.97(1)Å] and oxygen [Cu–O=2.019(8)Å] atoms of the amino end glycine residue and to another Cu(II) through one oxygen atom [Cu–O=1.931(9)Å] of the terminal carboxyl group. This give rise to covalently bonded and infinite ···–Cu–tripeptide–Cu–··· chains. These chains are linked to one another by a network of H-bonds involving the water molecules and bromide ions. The Cu(II) ion is in a distorted tetragonal pyramidal coordination polyhedron. At the corner of the base of the pyramid are the terminal glycine nitrogen and oxygen atoms of one tripeptide, a carboxylic oxygen of another tripeptide and a bromide ion. The fivefold coordination is completed with a water molecule at the top of the pyramid [Cu–Ow=2.286(9)Å]. For all orientations of the applied magnetic field the single crystal EPR spectra display a single anisotropic exchange collapsed resonance without hyperfine structure. Its position was measured in three perpendicular planes and the crystal g-tensor evaluated from the data. This tensor is interpreted in terms of the contributing Cu(II) complexes in the unit cell to deduce the principal values g1 = 2.273, g2 = 2.050 and g3 = 2.131 for the molecular gyromagnetic tensor. We also discuss the magnitude of the exchange interaction between neighboring copper ions in the lattice on the basis of the features in the EPR spectra and the structural information.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021734820606
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Reaction of 2-methylnaphthalene with hexachlorocyclopentadiene and structural characterization of a new addition-substitution product (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 787-790 
    Details
    ISSN: 1572-8854
    Keywords: 2-Methylnaphthalene ; hexachlorocyclopentadiene ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 2-Methylnaphthalene undergoes Diels-Alder addition and substitution with hexachlorocyclopentadiene to give two products, 1,2,3,4,5,6,7,8,13,13,14,14-dodecachloro-1,4,4a,4b,5,8,8a,12b-octahydro-10-methyl-1,4;5,8-dimethanotriphenylene 1 and 1,2,3,4,5,6,7,8,13,13,14,14-dodecachloro-1,4,4a,4b,5,8,8a,12b-octahydro-10-(1′,2′,3′,4′,5′-pentachlorocyclopentadienyl)methyl-1,4;5,8-dimethanotriphenylene 2. The molecular structure of 2 has been characterized by X-ray crystallography: C26H9Cl17, monoclinic, space group P21/c, with a = 15.316(3), b = 13.698(3), c = 16.116(3) Å, β = 96.113(3)°, and Z = 4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021819518557
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Synthesis and crystal structure of [(PhenH)(PhenH2)][BiCl6]·2H2O with different o-phenanthroline protonations (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 791-796 
    Details
    ISSN: 1572-8854
    Keywords: Halobismuthate(III) ; phenanthroline ; synthesis ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The reaction between bismuthate oxide and phen (1,10-phenanthroline) in acid medium led to the isolation of the unusual [(PhenH)(PhenH2)][BiCl6]·2H2O derivative, which has been characterized by X-ray analysis and IR spectroscopy. The compound crystallizes in the triclinic space group $$[\text[P\bar 1]]$$ with a = 8.313(2), b = 9.349(2), c = 9.807(3) Å, α = 86.39(3), β = 110.27(3) and γ = 106.48(3)°. The crystal structure is made of [BiCl6]3− anions and [(PhenH)(PhenH2)]3+ cations. A network of hydrogen bond interactions involving the two clathrated water molecules, the phenanthroline moiety and the chlorines characterizes the entire structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021871502627
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Tris-(thiocyanato)-bis-(hexamethylenetetramine)-nona-(aquo) lanthanum(III): synthesis, crystal structure, IR and Raman characterization (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 879-884 
    Details
    ISSN: 1572-8854
    Keywords: Lanthanum complex ; hexamethylenetetramine ; IR spectra ; thiocyanates ; coordination number nine ; tricapped trigonal prism ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound (LaC15H42N11O9S3) was prepared and characterized by means of X-ray, IR and Raman measurements. The crystals are orthorhombic: Pnma (No. 62), a = 21.117(2), b = 14.736(2), c = 10.082(1) Å, and Z = 4. The structure consists of polyhedra with a La(III) ion in the center of them and hexamethylene molecules, which link these polyhedra. Each La(III) ion coordinates seven molecules of water and two thiocyanate ions via nitrogen atoms. The IR and Raman spectra, which have been obtained and interpreted, are in good agreement with X-ray results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022846402229
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Preparation and crystal structures of the Ce(IV) β-diketonates, [Ce(tmhd)4] and [Ce(pmhd)4] (tmhd =2,2,6,6-tetramethylheptane-3,5-dionate and pmhd = 1-phenyl-5-methylhexane-1,3-dionate) (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 267-276 
    Details
    ISSN: 1572-8854
    Keywords: Cerium(IV) ; β-diketonate ; volatility ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The cerium(IV) β-diketonate compounds [Ce(β-diket)4] [where β-diket = tmhd (2,2,6,6-tetramethylheptane-3,5-dionate) 1, pmhd (1-phenyl-5-methylhexane-1,3-dionate) 2] were prepared by reacting cerium(IV) ammonium nitrate [CAN; Ce(NH4)2(NO3)6] with the respective Na(β-diket) compound in ethanol, and structurally characterized by single crystal X-ray diffraction. Compound 1 crystallizes in the triclinic space group $$P \bar 1$$ with a = 12.472(4), b = 19.972(5), c = 21.436(3) Å, α = 97.05(7), β = 90.16(2), γ = 106.55(3)°, V = 5076(2) Å3, Z = 4, T = 150(2) K. Compound 2 crystallizes in the monoclinic space group P21/n. with a = 14.817(6), b = 17.123(6), c = 19.146(3) Å, β = 105.46(4)°, V = 4682(3) Å3, Z = 4, T = 150(2) K. Crystals of 1 contain two independent [Ce(tmhd)4] molecules, with four chelating tmhd ligands bonded to each metal in a distorted dodecahedral arrangement; the cerium atom in 2 is also bonded to four chelating pmhd ligands but in this case the coordination geometry is closer to square antiprism. Both complexes are air and moisture stable. Sublimation studies reveal that 1 sublimes almost quantitatively, while 2 is comparatively involatile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021897102260
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Molecular structure and spectral characteristics of bis(S-methyl-N-(2-pyridyl)methylendithiocarbazato)nickel(II), (Ni(NNS)2) (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 871-874 
    Details
    ISSN: 1572-8854
    Keywords: Nickel(II) complex ; crystal structure ; Schiff base
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A nickel(II) complex of the pyridine-2-aldehyde Schiff base of S-methyldithiocarbazate (HNNS) has been synthesized and characterized by means of elemental analysis, IR and UV-vis spectra. The crystal structure of the complex has been determined by single-crystal X-ray diffraction. The complex crystallizes in the monoclinic, space P21/c, with a = 14.092(2), b = 16.886(2), c = 8.857(2)Å; β = 105.78(3) °, V = 2028.2(6) Å3, and Z = 4. The nickel atom is octahedrally coordinated by two uninegatively charged tridentate Schiff base in a mer-configuration via the pyridine nitrogen atom, azomethine nitrogen atom, and mecaptide sulfur atom.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022842301321
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Benztropine mesylate: crystal structure and kinetics of dehydration (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 885-892 
    Details
    ISSN: 1572-8854
    Keywords: Benztropine mesylate ; crystal structure ; thermal analysis ; dehydration kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of benztropine mesylate has been determined. It is orthorhombic, Pbca, with a = 12. 885(8)Å, b = 32.012(9)Å, and c = 10.027(3) Å. It exhibits similar packing to that seen in the previously reported crystal structure of benztropine mesylate monhydrate. X-ray powder diffraction patterns have been used to identify the anhydrous and monohydrate forms. The dehydration of the monohydrate follows a first-order reaction mechanism with activation energy of 92(8) kJ mol−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022898419067
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Synthesis and X-ray crystallographic characterization of [Cd(NO3)2(15-Crown-5)] and [Cd(NO3)2(18-Crown-6)] (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 521-527 
    Details
    ISSN: 1572-8854
    Keywords: Cadmium ; crown ether ; 15-crown-5 ; 18-crown-6 ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Reaction of 15-crown-5 or 18-crown-6 in 3:1 (v/v) CH3CN:CH3OH with Cd(NO3)2·4H2O followed by slow evaporation produces [Cd(NO3)2(15-crown-5)] or [Cd(NO3)2(18-crown-6)]. Crystals of [Cd(NO3)2(15-crown-5)] are orthorhombic with space group Pbca and cell parameters a = 13.562(5), b = 15.941(9), and c = 15.011(7) Å at 295 K. [Cd(NO3)2(18-crown-6)] crystallizes in the monoclinic space group C2/c with a = 11.235(2), b = 11.196(5), c = 15.385(3) Å, and β = 99.89(2)° at 295 K. The metal center in [Cd(NO3)2(15-crown-5)] rests atop the macrocyclic donor array with two cis-bound nitrate anions and adopts a distorted tricapped trigonal prismatic geometry. [Cd(NO3)2(18-crown-6)] resides on an equatorial two-fold rotation axis with Cd2+ coordinated in the 18-crown-6 cavity and the nitrate anions oriented in twisted trans positions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023239921542
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    The crystal and molecular structure of (−)—Crinine (C16H17NO3) (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 577-579 
    Details
    ISSN: 1572-8854
    Keywords: (−)—Crinine ; Pancratium ; alkaloid ; Amaryllidaceae ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract (−)—Crinine, C16H17NO3, is an alkaloid extracted from the bulbs of Pancratium maritimum L. (Amaryllidaceae). The compound crystallizes in the space group P212121 with cell dimensions a = 6.040(1), b = 12.382(1), c = 17.861(2) Å, with Z = 4. The molecule has five rings and an OH group. The N-containing, five-membered ring and the D ring have envelope conformations. The A and B rings have distorted chair and half-chair conformations, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023256425176
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 11
    Electronic Resource
    Electronic Resource
    Crystal structure of 2,2,4,7,7-pentamethyl-3,6-dithiaoctane tetracarbonyl tungsten(0) (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 217-220 
    Details
    ISSN: 1572-8854
    Keywords: Metal carbonyl complexes ; chelate complexes ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The x-ray crystal structure of the complex η2-PDOW(CO)4 (five-membered ring, PDO = 2, 2, 4, 7, 7-pentamethyl-3,6-dithiaoctane) is reported. The complex crystallizes in the monoclinic crystal system, space group P21/c, [#14] with unit cell parameters a = 14.002(14) Å, b = 9.340(10) Å, c = 15.094(12) Å, β = 92.67(4)°, V = 1972(3) Å3; Z = 4. The arrangement of the ligands around the metal atom is distorted from octahedral geometry. Large C–O bond distances and short W–C bond distances of the carbonyl groups located at a trans position with respect to PDO is indicative of a trans influence. The W–S(1) and W–S(2) bond distances of 2.545(3) and 2.545(2) Å, respectively, are shorter than observed for closely related complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022478528825
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    Crystal structure of tris(triphenylsiloxy)borane·triphenylsilanol (1:1) adduct (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 277-281 
    Details
    ISSN: 1572-8854
    Keywords: Triphenylsiloxy ; silanol ; borane ; crystal structure ; adduct
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound crystallizes in the triclinic space group $$P \bar 1$$ , with a = 14.458(6), b = 14.630(5), c = 14.721(8) Å, α = 79.75(2), β = 80.11(3), γ = 80.50(3)°, and Z = 2. The crystal structure consists of molecules of (Ph3SiO)3B and Ph3SiOH linked by an weak B···(silanol) acceptor-donor bond, additionally stabilized by OH(silanol)···O(siloxy) hydrogen bonds. The average B–O, Si–O distances and B–O–Si angle are 1.369, 1.649 Å and 137.2°, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021849219098
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    17α-acetoxy-17β-methyl-16β-phenyl-D-homo-4,6-pregnadiene-3,17a-dione: synthesis and crystal structure determination of a new rearranged pregnane derivative (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 487-491 
    Details
    ISSN: 1572-8854
    Keywords: Steroid ; pregnadiene ; x-ray diffraction ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound is C29H34O4, tetragonal, P43, a = b = 10.310(1), c = 23.871(2)Å. The A, B, C, and D rings adopt envelope, half-chair, chair, and distorted chair conformations, respectively. The phenyl ring is planar. The methyl substituents at the A/B, C/D, and at C(17) are axial; and the –OCOCH3 group at C(17) and phenyl ring at C(16) are equatorial. The molecules in the crystal are held together by van der Waals forces and several C–H···O hydrogen bond interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021729007943
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    Structure, absolute configuration, and conformation of the antimalarial compound, Artemisinin (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 539-543 
    Details
    ISSN: 1572-8854
    Keywords: Antimalarial ; crystal structure ; peroxy bridge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of the antimalarial compound Artemisinin (formerly known as Qinghaosu), C15H22O5 has been determined by direct methods. Crystals are orthorhombic colorless needles, space group P212121, Z = 4. D c = 1.299 g cm −3, with unit cell parameters a = 6.3543(9), b = 9.439(3), c= 24.066(4) Å. The molecule incorporates a fused ring system containing a six-membered ring C which includes an oxygen bridge and a peroxy-bridge. The ring C has a distorted boat conformation and the C - O - O - C torsion angle is 47.8(2)°. Rings A and D have symmetrical chair and distorted chair conformations, repectively. Ring junctions A/B, A/D, and C/D are cis, junction B/D is trans. All inter-molecular contacts are van der Waals. The absolute configuration of Artemisinin was determined from the refined value of the Flack x parameter. [The atomic coordinates given in a previous structure analysis, “Crystal Structure and Absolute Configuration of Qinghaosu,” Qinghaosu Research Group, Institute of Biophysics, Academica Sinica, Scientia Sinica, Vol. XXIII No. 3, 380 (1980), do not display the molecule in its absolute configuration.]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023244122450
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Cluster Complexes of Polythioether Macrocycles: The Synthesis and Molecular Structures of Ru6(CO)13(cis-SCH2 CHMe(CH2SCH2CHMe)2CH2)(μ6-C) and Ru6(CO)13(trans-SCH2 CHMe(CH2SCH2CHMe)2CH2)(μ6-C) (1998)
    Springer
    Journal of cluster science 9 (1998), S. 93-105 
    Details
    ISSN: 1572-8862
    Keywords: Ruthenium ; thioether macrocycle ; 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 a mixture of cis-3,7,11-trimethyl-1,5,9-trithiacyclododecane, cis-Me312S3, 1 and trans-3,7,11-trimethyl-l,5,9-trithiacyclododecane, trans-Me312S3, 2, with Ru6(CO)17(μ 6-C), 3, yielded three new cluster compounds Ru6(CO)13(μ-η3-cis-SCH2CHMe(CH2SCH2CHMe)2CH2)(μ 6-C) 4, and two isomers of Ru6(CO)13(μ-η3-cis-SCH2CHMe(CH2SCH2CHMe)2CH2)(μ 6-C) 5a and 5b. The molecular structures of 4 and 5b were established by single crystal X-ray diffraction analyses. In both complexes, the macrocycles have adopted tridentate coordination with one of the sulfur atoms in a bridging position. Two carbonyl ligands occupy bridging positions in each compound. Crystal Data for 4·Me2CO: space group=P21/n, a=11.295(1) Å, b=17.547(3) Å, c=20.318(3) Å, β=93.71(1)°, Z=4, 2900 reflections, R=0.025. Crystal Data for 5b·1.5 C6H6: space group=Pbca, a=31.8900(8) Å, b=23.4330(6) Å, c=21.6240(4) Å, Z=16, 12163 reflections, R=0.040.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022681523508
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    The First New Hydrogen-Bonded Heterohexanuclear Complex [(salen)Cu]4[(salen)Fe(H2O)2]2(ClO4)2: Molecular and Crystal Structure and Magnetic Properties (1998)
    Springer
    Journal of cluster science 9 (1998), S. 465-471 
    Details
    ISSN: 1572-8862
    Keywords: Mixed-metal cluster ; crystal structure ; magnetic properties
    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 preparation, magnetic properties, and crystal structure of [(salen)Cu]4[(salen)Fe(H2O)2]2(ClO4)2 via hydrogen bonding are described [salen=N,N′-ethylenebis (salicylideneiminate)]. Crystals are triclinic, of space group $$\rm P\bar 1$$ , with cell constants a=12.853(3), b=13.921(3), c=14.251(3) Å, α=68.68(3)°, β=87.86(3)°, γ=86.82(3)°, and Z=1. The structure was solved and refined to R=0.064 and R′=0.068. The structure comprises the hexanuclear units which result from the linking of four mononuclear fragments [(salen)Cu] and two mononuclear fragment [(salen)Fe(H2O)]+, through Cu -O ⋯ H -O -Fe -O -H ⋯ O -Cu hydrogen bonds of coordinating H2O. In this complex, FeIII ions are in almost square-planar surroundings. The temperature dependences of the magnetic susceptibilities of the complex have been studied in the 4.2–300 K range, indicating the presence of an antiferromagnetic interactions between metal ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021990516837
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    Direct Evidence for Metal Triangle Mobility within a Relatively Rigid Ligand Polytope: Dynamic Disorder in the X-Ray Crystal Structures of Ru3(CO)11(L), L=CN t Bu, PMe3, and Ru3(CO)9{P(OMe)3}3 (1998)
    Springer
    Journal of cluster science 9 (1998), S. 505-528 
    Details
    ISSN: 1572-8862
    Keywords: Dynamic disorder ; crystal structure ; ruthenium cluster
    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 disorder in the X-ray crystal structures of Ru3(CO)11(L), L=CN t Bu 1 and PMe3 3 has been re-examined. Crystallographic data for 1 at 100 K: C16H9NO11Ru3, space group P21/n, a=11.796(5), b=11.748(2), c=16.040(7) Å, β=109.81(3)°, Z=4, 6077 reflections, R=0.028. For 3 at 223 K: C14H9O11PRu3, space group P21/n, a=8.5971(15), b=12.391(7), c=40.345(8) Å, β=94.43(2)°, Z=8, 7966 reflections, R=0.031. The disorder present in 1 and 3 at room temperature disappears reversibly on cooling, showing that it is dynamic in origin. The ligator atoms of the isonitrile and phosphine ligands move by a maximum of ∼0.8 Å, indicating that the whole cluster does not rotate intact within the crystal lattice, but rather that the Ru3 triangle effectively oscillates within a relatively rigid ligand polyhedron. The crystal structure of Ru3(CO)9{P(OMe)3 3} 7, which crystallizes in triclinic (7-t) and monoclinic (7-m) modifications is also reported. Both modifications have two independent molecules in the asymmetric unit, and both modifications display dynamic disorder in the metal framework. Crystalllographic data for 7-t at 173 K: C18H27O18P3Ru3, space group P-1, a=11.8085(18), b=15.915(2), c=17.350(3) Å, α=99.929(14), β=101.811(14), γ=90.630(12)°, Z=4, 11242 reflections, R=0.048. For 7-m at 120 K: C18H27O18P3Ru3, space group P21/c, a=11.708(8), b=15.922(5), c=33.950(10) Å, β=99.29(4), Z=8, 10191 reflections, R=0.027.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021946701816
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    Electroless deposition of Ni–B, Co–B and Ni–Co–B alloys using dimethylamineborane as a reducing agent (1998)
    Springer
    Journal of applied electrochemistry 28 (1998), S. 559-563 
    Details
    ISSN: 1572-8838
    Keywords: electroless Ni–Co–B alloy ; dimethylamineborane ; complexing agent ; deposition rate ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Fundamental aspects of electroless Ni–B, Co–B and Ni–Co–B alloys have been systematically examined. The composition, crystal structure and deposition rate of the alloys were determined as a function of the concentration of reducing agent (dimethylamineborane) and complexing agents (tartrate, citrate, malonate and succinic acid), bath pH and Ni2+/Co2+ ratio. Changes in the deposition rate and metallurgical features of the alloys induced by the change in plating parameters are discussed, based on electrochemical polarization data and the formation enthalpy of the nickel and cobalt borides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003233715362
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    Electronic Resource
    Electronic Resource
    Structural and magnetic properties of a syn-anti carboxylate bridged one-dimensional copper(II) complex with ferromagnetic exchange interaction (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 771-777 
    Details
    ISSN: 1572-8854
    Keywords: Copper ; 1,10-phenanthroline ; trifluoroacetate ; crystal structure ; magnetic exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The compound [Cu(phen)(O2CCF3)2]n (phen = 1,10-phenanthroline) has been synthesized and its crystal structure determined. It crystallizes in monoclinic space group C2/c, with a = 19.229(7), b = 11.281(5), c = 7.621(2) Å, β = 104.305(12)°, and Z = 4. The crystal structure is polymeric, being built from infinite zigzag chains of trifluoroacetate bridged copper(II), with the phenanthroline ligands being stacked between the chains. The variable-temperature (13–300 K) magnetic susceptibility and ESR data are reported and a weak ferromagnetic exchange interaction is observed with the exchange parameter estimated as J = 2.9 cm−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021820729518
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 20
    Electronic Resource
    Electronic Resource
    Crystal structure of chloro(dicarbonyl) bis(acetonitrile) (π-2-methallyl) molybdenum(II) (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 839-841 
    Details
    ISSN: 1572-8854
    Keywords: π-allyl ; carbonyl ; nitrile ; chloro ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound crystallizes in the monoclinic spacegroup P21/m with a = 6.796(9), b = 12.145(14), c = 7.749(8)Å, β = 101.86(1)°, and Z = 2. The crystal structure consists of molecules of [MoCl(CO)2(NCMe)2(η3-C3H4Me-2)] with crystallographically imposed Cs symmetry and has a pseudo-octahedral geometry, with the π-allyl group trans- to the chloro group and the two cis-carbonyl and acetonitrile groups occupying the equatorial plane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021836022191
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 21
    Electronic Resource
    Electronic Resource
    The true nature of a complex of 1,10-phenanthroline with the ammonium ion; crystal structure of bis-phenanthrolineprotium perchlorate (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 611-619 
    Details
    ISSN: 1572-8854
    Keywords: 1,10-Phenanthroline ; bis-phenanthrolineprotium ; adduct ; crystal structure ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Herzog's reported bis-1,10-phenanthrolineammonium perchlorate, [(phen)2(NH4)](ClO4) is in fact the known 2:1 adduct of l,10-phenanthroline (phen) with perchloric acid, [(phen)2H](CIO4). Its crystal structure, mode of formation, and properties are described. The compound crystallizes in the triclinic space group with $$P\bar 1$$ , a = 7.2510(8), b = 13.120(2), c = 22.083(12) Å, α = 77.4550(12), β = 84.45(2), γ = 82.204(14)°, V = 2026.7(6) Å3, Z = 4, and D c = 1.510 g cm−3. It contains cationic columns of alternating 1,10-phenanthroline and its conjugate acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022460909589
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 22
    Electronic Resource
    Electronic Resource
    Crystal structure of the cytotoxic marine alkaloid 2-bromoleptoclinidinone (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 645-648 
    Details
    ISSN: 1572-8854
    Keywords: 2-Bromoleptoclinidinone ; marine alkaloid ; cytotoxic ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 2-Bromoleptoclinidinone methanol solvate, C18H8BrN3O·CH4O, crystallizes in the orthorhombic space group Pbca with a = 15.7013(2), b = 7.3308(1), and c = 26.9326(1) Å. The molecule is essentially planar, with the largest deviations occurring at bromine (−0.21 Å), carbonyl oxygen O(l) (+0.19 Å) and in ring-A (C(9) −0.15 Å, C(10) −0.15 Å). Methanol occupies the 1,10-phenanthroline-like metal binding site of the title compound.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022421328245
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 23
    Electronic Resource
    Electronic Resource
    Synthesis and crystal structure of N 12-(7-chloro-4-quinolinyl)-N 1,N 1-diethy1-1,12-diaminododecane (AQ-40) (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 925-929 
    Details
    ISSN: 1572-8854
    Keywords: Quinoline ; chloroquine ; antimalarial ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The preparation of N12-(7-chloro-4-quinolinyl)-N 1,N 1-diethyl-1,12-diaminododecane, AQ-40, was accomplished by a five-step process in 80% overall yield from 12-aminododecanoic acid and 4,7-dichloroquinoline. AQ-40 crystallizes as a monohydrate from reagent grade chloroform/ diethyl ether mixtures in the triclinc space group P-1 with a = 8.667(2), b = 8.9425(10), c = 17.217(3) Å, α = 99.34(1), β = 99.89(2), γ = 91.56(1)°, V = 1295.0 Å3 and Z = 2. The l2-(N 1,N 1-diethylamino)dodecyl side chain is in the fully extended conformation and the water molecule forms hydrogen bonds to the two tertiary nitrogen atoms as well as with the secondary amino group. The nitrogen of the secondary amino group bound to the four-position of the quinoline moiety is virtually planar. This together with the rather short C–N distance of 1.347(3) Å to the quinoline moiety suggests involvement of the lone pair on this nitrogen with the π system of the ring.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022810821793
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 24
    Electronic Resource
    Electronic Resource
    Molecular structure of trans-[Co(NH3)4(NH2CH3)Cl](ClO4)2 (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 69-72 
    Details
    ISSN: 1572-8854
    Keywords: Co(III) complex ; crystal structure ; kinetics ; steric effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound crystallizes in the orthorhombic space group Pnma, with a = 7.9209(5), b = 9.818(1), c = 16.867(2) Å, and Z = 4. The structure was solved employing 1864 independent x-ray reflections with I〉2σ(I) by Patterson and difference Fourier techniques and refined by full-matrix least-squares to R = 0.036. The trans-[CO(NH3)4(NH2CH3)Cl](ClO4)2 molecule is on a crystallographic mirror plane. The cobalt ion is in an elongated octahedral coordination with four equatorial ammonia ligands [average Co–N distance equal to 1.966(2) Å], an axial methylamine [Co–N=1.965(3)Å], and an axial chlorine ion [Co–Cl=2.2771(9)Å]. Kinetic steric effects of the complex are interpreted in terms of structural results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021786804676
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 25
    Electronic Resource
    Electronic Resource
    Crystal structure of NH3(CH2)2NH3BiCl5·2H2O (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 209-212 
    Details
    ISSN: 1572-8854
    Keywords: Bismuth ; crystal structure ; inorganic polymer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The ethylenediammonium pentachlorobismuthate(III) dihydrate salt is monoclinic with the following unit cell dimensions: a = 10.902(8)Å, b = 7.926(6)Å, c = 15.199(6)Å, β = 96.40(1)°, space group P21/n with Z = 4. The structure shows a layer arrangement parallel to the $$\vec a$$ axis: planes of the [Bi2Cl10]4− bioctahedra alternate with planes of [NH3(CH2)2NH3]2+ dications. The [Bi2Cl10]4− bioctahedra are connected through O(W)–H··· Cl hydrogen bonds, so that infinite unidimensional chains of composition [Bi2Cl10(H2O)2] n 4n− are formed in the structure parallel to the $$\vec a$$ axis. These chains are themselves interconnected by means of the N–H···Cl bonds originating from the [NH3(CH2)2NH3]2+ entities, forming a three-dimensional network.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022474327917
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 26
    Electronic Resource
    Electronic Resource
    The synthesis and X-ray structure of [Sr2(OSiPh3)4(NH3)5]·0.5C7H8 (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 221-226 
    Details
    ISSN: 1572-8854
    Keywords: Strontium ; triphenylsiloxy ; crystal structure ; ammonia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title complex [Sr2(OSiPh3)4(NH3)5]·0.5C7H8 was prepared by the reaction of strontium metal granules with triphenylsilanol in an ammoniacal-toluene solution at −40°C. It crystallizes in monoclinic space group P21/n with a = 14.465(3), b = 20.715 (6), c = 25.199(6) Å, β = 95.98(2)°, and Z = 4. The complex has a dimeric structure with one terminal and three bridging triphenylsiloxy ligands, the remaining coordination sites being occupied by five ammonia molecules. The central Sr2O4N5 moiety adopts a distorted M2X9 face-sharing bioctahedral arrangement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022430612896
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 27
    Electronic Resource
    Electronic Resource
    Crystal structure of mixed rubidium–ammonium hydrogen sulfate Rb0.7(NH4)0.3HSO4 at room temperature (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 335-338 
    Details
    ISSN: 1572-8854
    Keywords: Mixed rubidium–ammonium acid sulfate ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure of Rb0.7(NH4)0.3HSO4 has been determined by X-ray analysis. The mixed compound crystallizes in the monoclinic space group P21/n with unit cell parameters a = 14.374(6) Å, b = 4.618(6) Å, c = 14.412(2) Å, β = 118.03(2)°, V = 844.4(4) Å3, and D cal = 1.536 g cm−3 for Z = 8. The mixed compound Rb0.7(NH4)0.3HSO4 is a chain-based structure. The Rb+ and NH4 + cations are intercalated between chains, formed of HSO4 - groups linked with OH⋯O hydrogen-bonding. Rb0.7(NH4)0.3HSO4 presents a new type of structural arrangement different from those of pure RbHSO4 and NH4HSO4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022451822967
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 28
    Electronic Resource
    Electronic Resource
    The crystal and molecular structures of isoperezone, aminoperezone, and isoaminoperezone: a comparative study of their crystal packing (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 529-537 
    Details
    ISSN: 1572-8854
    Keywords: 2-[1,5-Dimethyl-4-hexenyl]-6-hydroxy-5-methyl-1,4-benzoquinone ; 2-[1,5-dimethyl-4-hexenyl]-6-amino-3-hydroxy-5-methyl-1,4-benzoquinone ; 2-[1,5-dimethyl-4-hexenyl]-3-amino-6-hydroxy-5-methyl-1,4-benzoquinone ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structures of isoperezone (1), aminoperezone (2), and isoaminoperezone (3) have been determined by single-crystal X-ray diffraction. Compound (1) yields orange crystals, orthorhombic space group P212121 with unit cell dimensions a = 6.271(6), b = 30.373(7), c = 7.257(1) Å, and Z = 4; compound (2) yields purple crystals, orthorhombic space group P212121 with unit cell dimensions a = 6.498(3), b = 7.500(1) c = 29.200(6) Å, and Z = 4; compound (3) yields purple crystals, monoclinic space group P21 with unit cell dimensions a = 7.354(1), b = 7.511(1), c = 13.283(1) Å, β = 102,07(1)°, and Z = 2. The side chains in (1)–(3) are oriented out of the plane of the quinone ring at an angle of 124, 144, and 97°, respectively. The molecules in the crystal are held together by hydrogen-bonding networks and van der Waals interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023292005612
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 29
    Electronic Resource
    Electronic Resource
    Crystal structure of [WI2(CO)3{P(OMe)3}2] (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 639-643 
    Details
    ISSN: 1572-8854
    Keywords: Tungsten(II) ; diiodo ; carbonyl ; trimethylphosphite ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract [WI2(CO)3{P(OMe)3}2]crystallizes in the orthorhombic space group Pca21, with a = 26.924(5), b = 10.726(2), c = 14.136(3) Å, and Z = 8. There are two molecules in the asymmetric unit, the metal atoms in each case being seven-coordinate with a capped fac-(CO)3 octahedral geometry. The molecular dimensions in the two molecules are nearly identical. The W–P distance to the capping atom 2.397 Å (average) is significantly shorter than the other W–P distance, 2.525 Å (average).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022469211406
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 30
    Electronic Resource
    Electronic Resource
    Asymmetric hetero-Diels-Alder reactions: X-ray structures of three novel chiral dihydropyrimidines (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 663-671 
    Details
    ISSN: 1572-8854
    Keywords: Pyrimidine ; carboxamide ; sulfonyl ; chiral ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Three novel dihydropyrimidine compounds N8,6-di(4-nitrophenyl)-(3R)-ethyl-(7R)-methyl-5-oxo-2,3,6,7-tetrahydrooxazolo[3,2,c] pyrimidine-8-carboxamide (2), N8,6-di((4-methylphenyl)-sulfonyl)-(3R)-ethyl-5-oxo-(7R)-phenyl-2,3,6,7-tetrahydrooxazolo [3,2,c]pyrimidine-8-carboxamide (3) and N8,6-di ((4-methylphenyl)sulfonyl)-(3R)-ethyl-(7R)-methyl-5-oxo-2,3,6,7-tetrahydrooxazolo[3,2,c] pyrimidine-8-carboxamide (4) have been prepared (from 2-amino-1-butanol of 64.4% e.e.) and structurally characterized by X-ray crystallography. All three compounds contain stereogenic centers, but the crystal of (2) chosen was found to be racemic whilst those of (3) and (4) were found to be homochiral. Compound (2) crystallizes in the monoclinic space group P21/c, with a = 17.958(4), b = 12.431(2), c = 9.653(2) Å, β = 96.20(3)°, U = 2142.3(7) Å3, Z = 4, and D c = 1.449 g cm−3. Compounds (3) and (4) both crystallize in the monoclinic space group P21, with a = 9.349(2), b = 5.824(5), c = 26.513(8) Å, β = 99.43(2)°, U = 1424.1(13) Å3, Z = 2 and D c = 1.389 g cm−3 for (3), and a = 5.9526(9), b = 16.3521(10), c = 13.2263(11) Å, β = 92.81(12)°, U = 1285.9(2) Å3, Z = 2 and D c = 1.378 g cm−3 for (4).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021791832534
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 31
    Electronic Resource
    Electronic Resource
    The synthesis and crystallographic characterization of the heterotrimetallic linear complex [Et4N][(Ph3P)2{CuS2MoS2Fe}Br2] (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 713-716 
    Details
    ISSN: 1572-8854
    Keywords: Heterotrimetallic sulfido cluster ; linear ; synthesis ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The complex Cu(PPh3)3I reacts with [Et4N]2MoS4 and FeBr2 to give the heterotrimetallic complexes [Et4N][(Ph3P)2{CuS2MoS2Fe}Br2] (1). [Et4N][(Ph3P)2{CuS2MoS2Fe}Br2] (1) crystallizes in the triclinic space group P-1, a = 13.537(4), b = 15.316(4), c = 12.381(4) Å, α = 105.16(2), β = 93.27(3), γ = 101.18(2)°, and V = 2415.0(12) Å3 for Z = 2. The three metal atoms of the structure [Et4N][(Ph3P)2{CuS2MoS2Fe}Br2] (1) are nearly distributed along a line, where three metal atoms (Mo, Cu, Fe) are each in an approximate tetrahedral coordination, the lengths Mo-Fe and Mo-Cu distances are 2.772(2) and 2.798(2) Å, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021756319330
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 32
    Electronic Resource
    Electronic Resource
    [CaSb2(EDTA)2(H2O)8]n: synthesis, crystal structure, and thermal behavior (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 447-452 
    Details
    ISSN: 1572-8854
    Keywords: Bimetallic EDTA complex ; crystal structure ; antimony
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The synthesis and crystal structure of a new EDTA complex, [CaSb2(EDTA)2(H2O)8]n, are reported. This compound crystallizes in the monoclinic space group P21/n, with a = 7.132(1) Å, b = 21.893(3) Å, c = 10.891(2) Å, β = 91.15(2)°. Sb(EDTA) entities are connected through carboxylate bridges to the calcium atoms resulting in layers parallel to the (101) plane. These layers are linked through a weak Sb···O bond (3.171 Å). Pyrolysis of this complex under sulfur vapor, between 400 and 800°C, leads to a mixture of the monometallic sulfides. Pyrolysis in air above 700°C allows the easy preparation of the mixed oxide CaSb2O6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021716605217
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 33
    Electronic Resource
    Electronic Resource
    Crystal structure of (3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocen-2-yl) carboxylic acid and its bis-[W(CO)5] complex·0.5C5H12: Conformation of 1,1′-diphosphaferrocenes (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 621-628 
    Details
    ISSN: 1572-8854
    Keywords: 1-1′-Diphosphaferrocene conformation ; P···P secondary bonding ; bis-[W(CO)5](l,l′-diphosphaferrocene system) ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structures of (3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocen-2-yl)carboxylic acid (1) and its bis-[W(CO)5] pentane solvate complex (2) have been determined by X-ray analysis. The compound 1 crystallizes in the monoclinic P21 /n space group with Z = 4; a = 7.8404(9), b = 14.9441(16), c = 11.7730(14) Å, β = 92.773(10)°, V = 1377.8(3) Å3, and Dcalc = 1.553 g cm−3. The compound 2 crystallizes in the triclinic $$P\bar 1$$ space group with two complex molecules and one pentane molecule in the unit cell. Cell parameters: a = 10.7070(2), b = 12.577(2), c = 13.239(3) Å, α = 84.00(2), β = 77.58(1), γ = 66.06(1)°, V = 1591.0(5) Å3, and Dcalc = 2.100 g cm−3 .The fully eclipsed conformation of the phospholyl rings with P···P secondary bonding of 3.353(1) Å is observed in 1 and a partially eclipsed conformation is found in 2. The 10 possible conformations of 1,1′-diphosphaferrocenes were described as the function of conformational parameter θ and observed geometry of the phospholyl rings.7 We suppose that the earlier conclusions concerning the destabilizing nature of 1,1′-diphosphaferrocene conformations with θ 〈 100° cannot be considered as general. The mode of W – P coordination, the structural changes of 1 by W(CO)5 coordination, the structural effect of phospholyl rings substitution by the –COOH group, and hydrogen bonds are analyzed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022413026427
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 34
    Electronic Resource
    Electronic Resource
    Crystal structure of [Co(o-SC6H4NH2){P(OMe)3}3]PF6 (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 635-638 
    Details
    ISSN: 1572-8854
    Keywords: Cobalt(II) ; 2-aminobenzenethiol ; trimethylphosphite ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A cobalt-thiolato-phosphite complex [Co(o-SC6H4NH2){P(OMe)3}3]PF6 has been prepared and characterized by X-ray crystallography. The complex crystallizes in the triclinic space group $$P\bar 1$$ with a = 10.590(4), b = 11.122(3), c = 13.577(5) Å, α = 101.85(1), β = 108.50(1), γ = 101.75(1)°, V = 1420.6(8) Å3, and Z = 2. The structure comprises discrete [Co(o-SC6H4NH2){P(OMe)3}3]+ cations and PF 6 − anions where the metal atom is coordinated in a highly distorted square-pyramidal environment by one chelate o-SC6H4NH 2 − (abt) and two P(OMe)3 ligands in the basal positions, and a third P(OMe)3 in the axial site with Co–N,, 1.847(5), Co–S, 2.166(2), Co–P, 2.157(2), 2.147(2), and 2.125(2) Å.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022417127336
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 35
    Electronic Resource
    Electronic Resource
    Crystal Structure of the Sought-After Tetrameric [(PDBP)AgCl]4 Cluster (PDBP=5-Phenyldibenzophosphole) (1998)
    Springer
    Journal of cluster science 9 (1998), S. 547-554 
    Details
    ISSN: 1572-8862
    Keywords: Silver cluster ; crystal structure ; tetrameric cluster
    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 sought-after member of the [(PDBP) n AgX] m (n, m=1,4; 2,2; 3,1; PDBP=5-Phenyldibenzophosphole, X=halides) series, the tetrameric [(PDBP)AgCl]4 cluster has been prepared and structurally characterized. The [P4Ag4Cl4] cluster core of [(PDBP)AgCl]4 bears striking similarity to that of [(Ph3P)AgCl]4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021950902725
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 36
    Electronic Resource
    Electronic Resource
    Crystal, Molecular, and Electronic Structure of 1-Acetyl-indoline and Derivatives (1998)
    Springer
    Structural chemistry 9 (1998), S. 365-373 
    Details
    ISSN: 1572-9001
    Keywords: 1-Acetyl-indoline ; crystal structure ; electronic structure ; AM1 calculation ; CI calculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The crystal and molecular structures of the following molecules have been determined: 1-acetyl-indoline, 1-acetyl-5-nitro-indoline, l-acetyl-5-nitro-7-bromo-indoline, 1-acetyl-5-bromo-7-nitroindoline, and l-acetyl-5-bromo-7-nitro-indol. Molecular orbital calculations are performed for these compounds and two related species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022419111660
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 37
    Electronic Resource
    Electronic Resource
    Supramolecular Structure Formed from H-Bonding of Ferrocenyl Carbonyl Propanoic Acid and 4,4'-Bipyridine (1998)
    Springer
    Molecular engineering 8 (1998), S. 25-29 
    Details
    ISSN: 1572-8951
    Keywords: hydrogen bond ; ferrocenyl carbonyl proanoic ; supermolecule ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Selective recognition in the title compound, (C14H14FeO3)2 ċ (C10H8N2), between ferrocenyl carbonyl propanoic acid and 4,4'-bipyridine through strong O–-HċN intermolecular hydrogen bonds results in a novel supramolecular architecture. Its crystal structure has been solved by single-crystal X-ray diffraction methods while its characterization has been studied by IR and DSC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008279517986
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 38
    Electronic Resource
    Electronic Resource
    Molecular Structure of a Chromatographic Chiral Selector Based on a Terguride Derivative (1998)
    Springer
    Structural chemistry 9 (1998), S. 39-45 
    Details
    ISSN: 1572-9001
    Keywords: Enantioselective chromatographic technique ; chiral selector ; ergot alkaloid derivative ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The structure of (+)1-(3-allylpropyl)-(5R,8S,10R)-N,N-diethyl-N′-[6-methylergolin-8-yl]urea, C22H33N4O (allyl-terguride), has been determined as part of a study on the chiral recognition mechanism of ergot alkaloids when they are used as the chiral stationary phase for the separation of racemic mixtures in liquid chromatographic methods. At the pH of the solution used for the crystallization, the molecules of allyl-terguride are protonated at N(6). All bond distances and angles are in the expected ranges. In the asymmetric unit one hydroxide ion is present. Hydrogen bonds join molecules of allyl-terguride in pairs along the b axis, connecting O(2) of the hydroxide ion to O(1) of one molecule and to N(2) and N(6) of another.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022435615295
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 39
    Electronic Resource
    Electronic Resource
    Role of MnO on the Mullitization Behavior of Al2 O3-SiO2 Gels (1998)
    Springer
    Journal of sol gel science and technology 13 (1998), S. 987-990 
    Details
    ISSN: 1573-4846
    Keywords: mullite ; MnO ; crystal structure ; electronic paramagnetic resonance (EPR) ; sol-gel chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Gels were synthesized from solutions of tetraethylorthosilicate (TEOS) and aluminium nitrate (with and without manganese nitrate). The structural evolution of the gels as a function of manganese content and heat-treatment temperature was studied by visible spectrophotometry (VIS), electron paramagnetic resonance (EPR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the presence of manganese can induce mullitization at lower temperatures. However, the effect of manganese depends on its content and how it enters into the mullite structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008652129890
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 40
    Electronic Resource
    Electronic Resource
    Accuracy of Secondary Structure and Solvent Accessibility Predictions for a Clostridial Neurotoxin C-Fragment (1998)
    Springer
    The protein journal 17 (1998), S. 311-318 
    Details
    ISSN: 1573-4943
    Keywords: Artificial neural network ; crystal structure ; statistics ; tetanus toxin ; botulinum neurotoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Earlier studies used Rost and Sander's artificial neural network [(1993a), J. Mol. Biol. 232, 584–599] to predict the secondary structures [Lebeda and Olson (1994), Proteins 20, 293–300] and residue solvent accessibilities [Lebeda and Olson (1997), J. Protein Chem. 16, 607–618] of the clostridial neurotoxins. Because the X-ray crystal structure of the 50-kDa C-terminal half of the heavy chain of tetanus toxin was recently determined, this report evaluates the accuracy of these network-derived predictions. For this predominantly β-strand-containing fragment, predictions, on a per-residue basis, for both secondary structure and solvent accessibility were about 70% accurate. A more flexible and realistic analysis based on overlapping segments yielded accuracies of over 80% for the three-state secondary structure and for the two-state accessibility predictions. Because the accuracies of these predictions are comparable to those made by Rost and Sander using a dataset of 126 nonhomologous globular proteins, our predictions provide a quantitative foundation for gauging the results when building by homology the structures of related proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022599014617
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 41
    Electronic Resource
    Electronic Resource
    Identification of proton transfer pathways in the X-ray crystal structure of the bacterial reaction center from Rhodobacter sphaeroides (1998)
    Springer
    Photosynthesis research 55 (1998), S. 119-125 
    Details
    ISSN: 1573-5079
    Keywords: bacterial photosynthesis ; crystal structure ; electron transfer ; proton transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Structural features that have important implications for the fundamental process of transmembrane proton transfer are examined in the recently published high resolution atomic structures of the reaction center (RC) from Rhodobacter sphaeroides in the dark adapted state (DQAQB) and the charged separated state (D+QAQB −); the latter is the active state for proton transfer to the semiquinone. The structures have been determined at 2.2 Å and 2.6 Å resolution, respectively, as reported by Stowell et al. (1997) [Science 276: 812–816]. Three possible proton transfer pathways (P1, P2, P3) consisting of water molecules and/or protonatable residues were identified which connect the QB binding region with the cytoplasmic exposed surface at Asp H224 & Asp M240 (P1), Tyr M3 (P2) and Asp M17 (P3). All three represent possible pathways for proton transfer into the RC. P1 contains an uninterrupted chain of water molecules. This path could, in addition, facilitate the exchange of quinone for quinol during the photocycle by allowing water to move into and out of the binding pocket. Located near these pathways is a cluster of electrostatically interacting acid residues (Asp-L213, Glu-H173, Asp-M17, Asp H124, Asp-L210 and Asp H170) each being within 4.5 Å of a neighboring carboxylic acid or a bridging water molecule. This cluster could serve as an internal ‘proton reservoir’ facilitating fast protonation of QB − that could occur at a rate greater than that attainable by proton uptake from solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006047519260
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 42
    Electronic Resource
    Electronic Resource
    Cytochrome c Oxidase (Heme aa 3) from Paracoccus denitrificans: Analysis of Mutations in Putative Proton Channels of Subunit I (1998)
    Springer
    Journal of bioenergetics and biomembranes 30 (1998), S. 89-97 
    Details
    ISSN: 1573-6881
    Keywords: Terminal oxidase ; redox coupling ; electrochemical gradient ; electron transport ; energy transduction ; proton translocation ; crystal structure ; site-directed mutagenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract One of the challenging features of energy-transducing terminal oxidases, like the aa 3 cytochrome c oxidase of Paracoccus denitrificans, is the translocation of protons across the cytoplasmic membrane, which is coupled to the transfer of electrons to oxygen. As a prerequisite for a more advanced examination of the enzymatic properties, several amino acid residues, selected on the basis of recent three-dimensional structure determinations, were exchanged in subunit I of the Paracoccus enzyme by site-directed mutagenesis. The properties of the mutated oxidases were analyzed by different methods to elucidate whether they are involved in the coupled and coordinated transfer of protons via two different pathways either to the site of oxygen reduction or through the enzyme from the cytoplasm to the periplasmic side.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020515713103
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 43
    Electronic Resource
    Electronic Resource
    Effect of M and M-Ca Substitution on the Structure and Superconductivity of GdBa2Cu3O7−δ [M = Mo, Hf ] (1998)
    Springer
    Journal of superconductivity 11 (1998), S. 285-290 
    Details
    ISSN: 1572-9605
    Keywords: GdBa2Cu3O7−δ ; Ca substitution ; Mo substitution ; Hf substitution ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The structural and superconducting properties of (Gd1−x−y Ca y M x )Ba2Cu3O z with M = Mo, Hf are investigated using X-ray diffraction, electrical resistivity, and oxygen content measurements. The effect of increasing the Mo concentration in (Gd1−x Mo x )Ba2Cu3O z changes the structure from orthorhombic to tetragonal accompanied by a large increase in resistivity and a fast decrease in T c at the rate of 1.9 K per at.% of Mo, unlike that of Hf substitution in (Gd1−x Hf x )Ba2Cu3O z , which maintains the orthorhombic structure and decreases T c very slowly at the rate of 0.6 K per atm.% of Hf with nearly no change in resistivity. The suppression of T c by M = Mo, Hf can be counterbalanced by hole doping by Ca which increases T c with increasing Ca content showing maximum compensation for Mo. A comparative study of M = Mo, Hf doped samples in (Gd1−x−y Ca y M x )Ba2Cu3O z indicates that the valence of the dopant M = Mo4+,6+, Hf4+ and its ionic radius play an important role in controlling the structural and superconducting properties of the systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022644203794
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 44
    Electronic Resource
    Electronic Resource
    A general method of domain closure is applied to phosphoglycerate kinase and the result compared with the crystal structure of a closed conformation of the enzyme (1998)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 30 (1998), S. 372-380 
    Details
    ISSN: 0887-3585
    Keywords: protein modeling ; crystal structure ; conformation change ; prediction ; mechanism ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The occurrence of large domain motions associated with the mechanism of action of many proteins is well established. We present a general method of predicting domain closure applicable to proteins containing domains separated by an apparent hinge. The method attempts to allow for natural directional bias within the closing protein by repeatedly applying a weak pulling force over a short distance between pairs of atoms chosen at random in the two domains in question. Appropriate parameters governing the pulling function were determined empirically. The method was applied to the bi-lobal protein PGK and a closed-form activated ternary complex generated for Bacillus stearothermophilus PGK. This model was compared with the recently determined crystal structure of closed-form Trypanosoma brucei PGK. The model predicts the correct hinge regions, although the magnitude of movement at one hinge point was overestimated, and provides a reasonable representation of the closed-form ternary complex. Proteins 30:372-380, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 45
    Electronic Resource
    Electronic Resource
    Full-matrix least-squares refinement of lysozymes and analysis of anisotropic thermal motion (1998)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 30 (1998), S. 232-243 
    Details
    ISSN: 0887-3585
    Keywords: turkey lysozyme ; human lysozyme ; crystal structure ; protein structure ; structure refinement ; protein crystal ; atomic resolution ; rigid-body motion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Crystal structures of turkey egg lysozyme (TEL) and human lysozyme (HL) were refined by full-matrix least-squares method using anisotropic temperature factors. The refinement converged at the conventional R-values of 0.104 (TEL) and 0.115 (HL) for reflections with Fo 〉 0 to the resolution of 1.12 Å and 1.15 Å, respectively. The estimated r.m.s. coordinate errors for protein atoms were 0.031 Å (TEL) and 0.034 Å (HL). The introduction of anisotropic temperature factors markedly reduced the R-value but did not significantly affect the main chain coordinates. The degree of anisotropy of atomic thermal motion has strong positive correlation with the square of distance from the molecular centroid. The ratio of the radial component of thermal ellipsoid to the r.m.s. magnitude of three principal components has negative correlation with the distance from the molecular centroid, suggesting the domination of libration rather than breathing motion. The TLS model was applied to elucidate the characteristics of the rigid-body motion. The TLS tensors were determined by the least-squares fit to observed temperature factors. The profile of the magnitude of reproduced temperature factors by the TLS method well fitted to that of observed Beqv. However, considerable disagreement was observed in the shape and orientation of thermal ellipsoid for atoms with large temperature factors, indicating the large contribution of local motion. The upper estimate of the external motion, 67% (TEL) and 61% (HL) of Beqv, was deduced from the plot of the magnitude of TLS tensors determined for main chain atoms which were grouped into shells according to the distance from the center of libration. In the external motion, the translational portion is predominant and the contribution of libration and screw motion is relatively small. The internal motion, estimated by subtracting the upper estimate of the external motion from the observed temperature factor, is very similar between TEL and HL in spite of the difference in 54 of 130 amino acid residues and in crystal packing, being suggested to reflect the intrinsic internal motion of chicken-type lysozymes. Proteins 30:232-243, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 46
    Electronic Resource
    Electronic Resource
    Role of water in plasticity, stability, and action of proteins: The crystal structures of lysozyme at very low levels of hydration (1998)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 32 (1998), S. 229-240 
    Details
    ISSN: 0887-3585
    Keywords: active-site geometry ; crystal structure ; enzyme action ; protein hydration ; protein mobility ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Earlier studies involving water-mediated transformations in lysozyme and ribonuclease A have shown that the overall movements in the protein molecule consequent to the reduction in the amount of surrounding water are similar to those that occur during enzyme action, thus highlighting the relationship among hydration, plasticity, and action of these enzymes. Monoclinic lysozyme retains its crystallinity even when the level of hydration is reduced further below that necessary for activity (about 0.2 gram of water per gram of protein). In order to gain insights into the role of water in the stability and the plasticity of the protein molecule and the geometrical basis for the loss of activity that accompanies dehydration, the crystal structures of monoclinic lysozyme with solvent contents of 17.6%, 16.9%, and 9.4% were determined and refined. A detailed comparison of these forms with the normally hydrated forms show that the C-terminal segment (residues 88-129) of domain I and the main loop (residues 65-73) in domain II exhibit large deviations in atomic positions when the solvent content is reduced, although the three-dimensional structure is essentially preserved. Many crucial water bridges between different regions of the molecule are conserved in spite of differences in detail, even when the level of hydration is reduced well below that required for activity. The loss of activity that accompany dehydration appears to be caused by the removal of functionally important water molecules from the active-site region and the reduction in the size of the substrate binding cleft. Proteins 32:229-240, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 47
    Electronic Resource
    Electronic Resource
    Crystal Structure of a p-Benzylcalix[5]arene- pyridine Complex (1998)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 31 (1998), S. 357-365 
    Details
    ISSN: 1573-1111
    Keywords: calixarenes ; crystal structure ; supramolecular assembly
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract p-Benzylcalix[5]arene.3py (py = pyridine) (1) crystallizes in the triclinic space group P1, a = 10.641(3), b = 13.975(3), c = 24.052(12) Å, α = 94.60(4), β = 91.51(4), γ = 111.46(2)°, V = 3312(4) Å3, Z = 2. Refinement led to a final conventional R value of 0.065 for 5457 reflections. The calixarene is in a distorted cone conformation. Two pyridine molecules are hydrogen bonded to phenolic oxygen atoms and one of them is included in the hydrophobic cavity of the neighboring calixarene molecule along the a axis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007964510691
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 48
    Electronic Resource
    Electronic Resource
    A New Clathrate: Synthesis and Crystal Structure of the [36]ene-O6N8/THF (1:2) Clathrate (1998)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 30 (1998), S. 13-19 
    Details
    ISSN: 1573-1111
    Keywords: THF clathrate ; Schiff base macrocycle ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new clathrate inclusion compound of 2,3:11,12:20,21:29,30-tetrabenzo-1,13,16,19,31,34-hexaoxa-5,6,8,9,23,24,26,27- octaaza-7,25-dithioketone-2,3:4,5:9,10:11,12:22,23:27,28:29,30-cyclo-[36]ene([ 36]eneO6N8), which contains THF, has been prepared and crystallizes in the monoclinic space group P21/n with a = 9.829(5)Å, b = 24.23(1)Å, c = 10.181(9)Å, β = 92.93(5)-. Each unit cell contains two [36]ene-O6N8 molecules and four THF molecules. The [36]ene-O6N8 molecule lies on the crystallographic centre of symmetry and a pair of the THF molecules with half-chair conformation are located within rectangular channels formed by the macrocycle molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007904912978
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 49
    Electronic Resource
    Electronic Resource
    The Menschutkin reaction of benzyl p-toluenesulfonates with N,N-dimethylanilines. Evidence for the duality of SN1 and SN2 mechanisms (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 254-260 
    Details
    ISSN: 0894-3230
    Keywords: Menschutkin reaction ; duality of SN1, SN2 mechanisms ; benzyl tosylates ; Yukawa-Tsuno equation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rate data for the Menschutkin reaction between strongly activated Z-substituted benzyl p-toluenesulfonates and Y-substituted N,N-dimethylanilines in acetonitrile at 35 °C fit the equation, kobs  =  k1 + k2 [DMA], which is consistent with concurrent first- and second-order processes. The k1 and k2 values for each substrate were separated based on the above equation. The SN1 rate constant, k1, is unaffected by the nature of the nucleophile, whereas the SN2 rate constant, k2, increased with the electron-donating substituent of the N,N-dimethylaniline. The substituent effect on the k1 values is linearly correlated by the Yukawa-Tsuno equation with ρ  =  -5.2 and r  =  1.3. The unimolecular reaction can be regarded as a classical SN1 mechanism. In contrast, that on the k2 values shows an upward curvature when analyzed by the Brown σ+ treatment. These results are ascribed to the simultaneous and independent occurrence of SN1 and SN2 mechanisms in the present Menschutkin reaction. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 50
    Electronic Resource
    Electronic Resource
    Editorial (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 231-231 
    Details
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No Abstract
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 51
    Electronic Resource
    Electronic Resource
    Solvent effects on infrared spectroscopic and calorimetric characteristics of aliphatic ketones in binary solvent mixtures (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 283-289 
    Details
    ISSN: 0894-3230
    Keywords: calorimetry ; IR spectra ; ketones ; solvation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solution enthalpies of n-hexane, acetone, butan-2-one and octan-2-one in a series of tetrachloromethane-acetonitrile mixtures and the carbonyl stretching absorption frequencies in the IR spectra of these ketones were determined. It was found that over the whole range of concentrations (varying from neat tetrachloromethane up to neat acetonitrile) the solvation enthalpy of these compounds can be obtained additively from the contributions of the alkyl and carbonyl fragments. The solvent effect on the solvation enthalpy of the carbonyl group was found to be satisfactorily correlated with the corresponding IR frequency shifts of the C=O group. It was also found that the sensitivities of the carbonyl IR frequencies to the solvent composition are different for various ketones. From both IR and calorimetric data, the preferential solvation parameters were evaluated. The differences between the IR spectroscopic and calorimetric data are discussed. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 52
    Electronic Resource
    Electronic Resource
    Solvent effects on C=O stretching frequencies of some 1-substituted 2-pyrrolidinones (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 261-272 
    Details
    ISSN: 0894-3230
    Keywords: 1-substituted 2-pyrrolidinones ; C=O stretching frequencies ; solvent effects ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In an effort to model solute-solvent interactions, the C=O stretching frequencies of five 1-substituted 2-pyrrolidinones and four other carbonyl-containing compounds were measured for 30 common solvents. These were then correlated with four empirical parameter sets and one theoretical (computational) parameter set. While an empirical parameter set gave the best correlation equations, the theoretical parameter equations are physically and statistically significant. Solvent volume, polarizability and hydrogen bond donor acidity (capacity) terms are significant in the correlation equations. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 14 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 53
    Electronic Resource
    Electronic Resource
    Molecular orbital calculations on the P - S bond cleavage step in the hydroperoxidolysis of nerve agent VX (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 232-240 
    Details
    ISSN: 0894-3230
    Keywords: P - S bond cleavage ; hydroperoxidolysis ; nerve agent VX ; molecular orbital calculations ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The P - S bond cleavage process in the hydroperoxidolysis of a model system for the nerve agent VX was studied using ab initio and semiempirical molecular orbital methods. Aqueous solvation effects were included through single-point calculations using the semiempirical SM5.2PD/A continuum solvation model and geometries optimized at the HF/MIDI! level of theory. The predominant pathway for P - S bond cleavage involves pseudorotation of a low-energy trigonal bipyramidal intermediate followed by apical ligand ejection. In aqueous solution, the free energy barriers for these processes are found to be 14.3 and 4.6 kcal mol-1, respectively, with electronic energies calculated at the MP2/cc-pVDZ//HF/MIDI! level of theory. By comparison with another continuum model of solvation (PCM), it is concluded that the SM5.2PD/A model performs well even for hypervalent phosphorus species, in spite of not having included any such molecules in the model's parameterization set. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 54
    Electronic Resource
    Electronic Resource
    Gas-phase thermolysis of N-methyl-N-phenyl-tert-butylsulfenamide and morpholinyl-tert-butylsulfenamide (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 407-410 
    Details
    ISSN: 0894-3230
    Keywords: gas-phase thermolysis ; N-methyl-N-phenyl-tert-butylsulfenamide ; morpholinyl-tert-butylsulfenamide ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: N-Methyl-N-phenyl-tert-butylsulfenamide (MPSA) and morpholinyl-tert-butylsulfenamide (MOSA) were thermolyzed in a stirred-flow reactor at temperatures of 340-390 °C and pressures of 7-13 Torr, using toluene as carrier gas, at residence times of 0.3-1.3 s. Isobutene was formed in 99% yield through first-order reactions having the following Arrhenius parameters (A,s-1, Ea, kJ mol-1): MPSA, log A  =  12.41 ± 0.02, Ea  =  158.8 ± 0.2; MOSA, log A  =  12.91 ± 0.22, Ea  =  159 ± 3. It is proposed that the elimination of isobutene takes place by unimolecular reaction mechanisms involving polar, four-center cyclic transition states, forming S-unsubstituted thiohydroxylamines as co-products. Thermochemical parameters, estimated by semiempirical AM1 calculations, are reported for the latter and for the parent molecules. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 55
    Electronic Resource
    Electronic Resource
    NMR and semi-empirical study of the tautomerism of­2,2′-bisbenzimidazolyl (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 411-418 
    Details
    ISSN: 0894-3230
    Keywords: 2,2′-bisbenzimidazolyl ; tautomerism ; NMR ; semi-empirical calculations ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A dynamic NMR study of the tautomerism of 2,2′-bisbenzimidazolyl in DMSO-d6 and a mechanistic interpretation of the process, based on a stepwise, single-proton transfer and formation of a zwitterionic intermediate, are presented. This interpretation is substantiated by semi-empirical calculations of the postulated intermediate and transition state, that yield results which are compared with previous studies on related aliphatic systems. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 56
    Electronic Resource
    Electronic Resource
    Effects of sulfenyl, sulfinyl and sulfonyl groups on acidities and homolytic bond dissociation energies of adjacent C - H and N - H bonds (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 397-406 
    Details
    ISSN: 0894-3230
    Keywords: bond dissociation energy ; acidity ; phenylsulfenylamides ; phenylsulfenylanilides ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Acidities and bond dissociation energies (BDEs) of the N-H bond in two phenylsulfenylamides, PhSNHBz and PhSNH-t-Bu, and four phenylsulfenylanilides, 4-GC6H4NHSPh, where G  =  MeO, H, Br and CN, were measured in order to compare the effects of substituents on acidities and BDEs of N - H bonds with those of C - H bonds. The effects of PhS groups on acidities and BDEs in a series of C - H acids were found to be comparable to those on acidities and BDEs of PhS in a similar series of N - H acids. Comparisons were also made of the effects of changing the oxidation state of sulfur in the series PhS, PhSO and PhSO2 on the acidities and BDEs of adjacent N - H and C - H bonds in weak acids. Hammett-type plots of pKHA values for phenyl benzyl sulfones (4-GC6H4CH2SO2Ph) and phenylsulfenylanilides (4-GC6H4NHSPh) were linear vs σp- values. A linear plot was obtained and explained for a plot of BDE of the N - H bonds in remotely substituted phenylsulfonylanilides with σ+ values. Plots of BDEs vs Eox(A-) were also linear for 4-substituted phenylsulfenylanilides (4-GC6H4NHSPh), phenylsulfonylanilides (4-GC6H4NHSO2Ph) and phenyl benzyl sulfones (4-GC6H4CH2SO2Ph). © 1998 John Wiley & Sons, Ltd.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 57
    Electronic Resource
    Electronic Resource
    17O NMR studies on α-diamides (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 387-391 
    Details
    ISSN: 0894-3230
    Keywords: α-diamides ; 17O NMR ; conformation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 17O NMR spectra of several α-diamides were obtained at natural isotopic abundance in acetonitrile solution in order to study the conformations of these compounds in solution. The 17O NMR shifts vary with the intercarbonyl dihedral angle α in a sense opposite to that observed for α-diketones. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 58
    Electronic Resource
    Electronic Resource
    Theoretical study of the tautomerism of 8-azaadenine (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 392-396 
    Details
    ISSN: 0894-3230
    Keywords: 8-azaadenine ; tautomerism ; theoretical study ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The prototropic tautomerism of 8-azaadenine (azaade) was studied theoretically by means of ab initio methods, in both the gas phase and aqueous solution. A number of tautomeric forms were not included in the calculations after applying a stepwise elimination procedure based on both AM1 and HF/6-31G* energy values. The tautomers 9H-azaade, 8H-azaade and 7H-azaade survived to this elimination and their optimized geometries and energies were calculated at the MP2/6-31*//HF/6-31G* level. To include the solvent effects, two self-consistent reaction field method were used: (1) Onsager's SCRF with multipolar expansion up to the hexadecapolar term and (2) the isodensity polarizable continuum method (IPCM). Both methods produce similar results, although the latter represents better the situation in aqueous solution. The stability order in solution, 8H- 〉 9H- 〉 7H-azaade, differs slightly from that found in the gas phase, implying that in general the electrostatic effects in solution are important, but the intrinsic stability of these species in the gas phase overcomes the solvent effect. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 59
    Electronic Resource
    Electronic Resource
    Editorial (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 377-377 
    Details
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No abstract.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 60
    Electronic Resource
    Electronic Resource
    Electrochemical study of the π* probe dye 5-nitro-5′-dimethylamino-2,2′-bisthiophene (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 419-425 
    Details
    ISSN: 0894-3230
    Keywords: 5-nitro-5′-dimethylamino-2,2′-bisthiophene ; π* probe dye ; cyclic voltammetry ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Cyclic voltamograms of the solvatochromic dye 5-nitro-5′-dimethylamino-2,2′-bisthiophene (1), introduced recently as a sensitive π* probe, were recorded in different solvents. An EPR spectrum of the anionic radical of 1 in DMSO was obtained and compared with other spectra of analogous substituted bisthiophene radicals. It was found that the presence of a donor- acceptor pair of substituents in 1-⋅ reduces significantly the rotational barrier of the radical compared with the unsubstituted bithienyl radical anion 2-⋅. This is the result of an electronic repulsion between the donor ring fragment and the added electron in the coplanar radical, which does not exist in 2-⋅. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 61
    Electronic Resource
    Electronic Resource
    Host-guest interactions of calix[4]resorcinarenes with benzene derivatives in conditions of reversed-phase high-performance liquid chromatography. Determination of stability constants (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 426-437 
    Details
    ISSN: 0894-3230
    Keywords: calix[4]resorcinarenes ; organophosphorus compounds ; solvatophobic interactions ; host-guest complexation ; high-performance liquid chromatography ; x-ray analysis ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Reversed-phase high-performance liquid chromatography [LiChrosorb RP-18,UV detection at 254 nm and acetonitrile-water (86:14,v/v) as mobile phase] was applied to studies of the host-guest complexation of tetraalkylcalix[4]resorcinareneoctols and their upper rim phosphoryl, sulfonyl and dialkylaminomethyl derivatives with some aromatic guests in the mobile phase. It was shown that the formation of the inclusion complexes results in changes in the retention of aromatic guests and improves their separation. Stability constants of the complexes were calculated from the dependences of the l/k′ values of the aromatic guest on the concentration of the calix[4]resorcinarene in the mobile phase. The molecular structure of 4,6,16,18-tetrahydroxy-10,12,22,24-tetrakis(dipropoxyphosphoryloxy)-2,8,14,20-tetramethylcalix[4]resorcinarene (12) was determined. Crystal data for 12 are P21/n, a  =  16.708(9) Å, b  =  18.683(6) Å, c  =  20.243(5) Å, β  =  95.75(3)°, V  =  6287(4) Å3 and Z  =  4. Compound 12 exists in a boat conformation, in which two opposite unsubstituted resorcinol rings of the macrocyclic skeleton lie in the plane formed by four methine bridges and two diphosphorylated rings are perpendicular to the plane. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 62
    Electronic Resource
    Electronic Resource
    Ab initio and molecular mechanics (MM3) calculations on alkyl- and arylboronic acids (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 378-386 
    Details
    ISSN: 0894-3230
    Keywords: alkylboronic acids ; arylboronic acids ; ab initio ; MM3 ; molecular mechanics ; force field parameters ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The boronic acid functional group has been incorporated into various biologically important compounds. In order to study this class of compounds better with molecular mechanics, five alkyl- and arylboronic acids were calculated using ab initio methods (Spartan) at the RHF/6-31G* level. MM3 force field parameters were developed based on the theoretically calculated geometries, vibrational spectra, and torsional profiles. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 63
    Electronic Resource
    Electronic Resource
    Base-catalysed hydrolysis of γ-lactones: reactivity-structure correlations for 3-(substituted phenoxy- and thiophenoxymethylene)-(Z )-1(3H )-isobenzofuranones (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 467-474 
    Details
    ISSN: 0894-3230
    Keywords: γ-lactones ; base-catalysed hydrolysis ; reactivity-structure correlations ; isobenzofuranones ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Rate coefficients were measured for the base-catalysed hydrolysis of a series of substituted 3-(phenoxy- or thiophenoxymethylene)-(Z)-1(3H)-isobenzfuranones (3-phenoxy- or thiophenoxymethylenephthalides) in 70% (v/v) aqueous dioxane at 30.0 °C, in addition to the carbonyl stretching frequencies in chloroform and tetrachloromethane following deconvolution and band separation, when required. The Hammett reaction constants for the alkaline hydrolysis of the 3-/4-substituted phenoxy and thiophenoxy series are ca 0.75 and 1.10, respectively. These results are related to electrostatic field and resonance effects. Successful correlations between the carbonyl stretching frequencies and substituent constants and the rates of alkaline hydrolysis were found. Computational studies using the semi-empirical AM1 method correctly model both the details of the mechanistic pathway and the substituent effects. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 64
    Electronic Resource
    Electronic Resource
    A new approach to the theoretical estimation of inductive constants (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 437-447 
    Details
    ISSN: 0894-3230
    Keywords: inductive constants ; theoretical estimation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new model of the inductive effect is proposed, allowing highly accurate theoretical calculations of inductive constants for a diversity of substituents, using a simple and readily available system of mathematics. According to this approach, the inductive effect of a substituent is considered in terms of the additive influence of its constituent atoms. A constant inherent capacity for inductive interaction with a reactive center (with a four-coordinate carbon atom chosen for such a center), represented by an atomic constant σA, is ascribed to each atom. Values of σA for a wide variety of atoms are determined, and their physical meaning is revealed to elucidate to a certain extent the physical nature of the inductive effect. In addition, the proposed model permits the convenient use in calculations of group constants σG characterizing the inductive power of groups. Values of σG are determined for molecular fragments that are most widely dealt with in organic chemistry, and the use of σA or σG constants and of their superposition is shown to have, in most cases, little or no effect on the accuracy and reproducibility of the results obtained. It is also shown that, in terms of the developed approach, the inductive effect of a substituent is closely associated with its conformation. Theoretical inductive constants were calculated for 427 organic, aromatic, organometallic and charged substituents, and they showed perfect correlation with the corresponding experimental values. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 65
    Electronic Resource
    Electronic Resource
    Oxidation of mandelic acid by alkaline potassium permanganate. A kinetic study (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 448-454 
    Details
    ISSN: 0894-3230
    Keywords: mandelic acid ; alkaline permanganate ; oxidation ; kinetics ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of the oxidation of mandelic acid (MA) by permanganate in aqueous alkaline medium at a constant ionic strength of 1.0 mol dm-3 were studied spectrophotometrically. The reaction shows first-order kinetics in [permanganate ion] and fractional order dependences in [MA] and [alkali]. Addition of products, manganate and aldehyde have no significant effect on the reaction rate. An increase in ionic strength and a decrease in dielectric constant of the medium increase the rate. The oxidation process in alkaline medium under the conditions employed in the present investigation proceeds first by formation of an alkali permanganate complex, which combines with mandelic acid to form another complex. The latter decomposes slowly followed by a fast reaction between the free radical of mandelic acid and another molecule of permanganate to give products. The reaction constants involved in the mechanism were derived. There is good agreement between the observed and calculated rate constants under different experimental conditions. The reaction was studied at different temperatures and activation parameters were computed with respect to the slow step of the proposed mechanism. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 66
    Electronic Resource
    Electronic Resource
    Selective arylation of exocyclic N-position of 2-pyrimidylnitrenium ion photolytically generated from tetrazolo-[1,5-a]pyrimidine in the presence of trifluoroacetic acid (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 478-484 
    Details
    ISSN: 0894-3230
    Keywords: Selective arylation ; exocyclic N-position ; 2-pyrimidylnitrenium ion ; tetrazolo[1,5a]pyrimidine ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Photo-reactions of tetrazolo[1,5-a]pyrimidine (1) with benzene (2a) and substituted benzenes (2b-f) in the presence of trifluoroacetic acid (TFA) gave 2-(2-, 3- and 4-substituted anilino)pyrimidines (3-5) together with 2-aminopyridine (6) and biphenyl (7) or diarylmethanes (8b, 8c and 8e). From the effect of heavy-atom solvent on the reactions, it is reasonable to assume that 3-5 are formed via a singlet species, but 6-8 via a triplet species. The intermediacy of 2-pyrimidylnitrenium ion is consistent with the evidence derived by the above effect, by a Hammett plot with ρ = -2.9 and by effects of solvent nucleophilicity and counter-anions. The selective exocyclic N-arylation giving 3-5 is discussed. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 67
    Electronic Resource
    Electronic Resource
    Synthesis, structural, conformational and pharmacological study of esters derived from 3-methyl-2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9α-ol as potential analgesics (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 125-132 
    Details
    ISSN: 0894-3230
    Keywords: 3-methyl-2, 4-diphenyl-3-azabicyclo[3.3.1]nonan-9α-ol esters ; analgesics ; synthesis ; structure ; conformation ; pharmacological assays ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of esters derived from 3-methyl-2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9α-ol (1) was synthesized and studied by 1H and 13C NMR spectroscopy, and the crystal structure of 3-methyl-2,4-diphenyl-9α-(3,5-dimethylbenzoyloxy)-3-azabicyclo[3.3.1]nonane (2) was determined by x-ray diffraction. The compounds studied display in CDCl3 a preferred flattened chair-chair conformation. This bicycle conformation is similar to that found for 2 in the crystal state. Pharmacological assays on mice were performed to evaluate drug-induced behavioral alteration, peripheral or central acute toxicity and analgesic activity. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 68
    Electronic Resource
    Electronic Resource
    Stereospecific nucleophilic trapping of encounter complexes between photoexcited 1-cyanonaphthalene and norbornadiene (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 101-108 
    Details
    ISSN: 0894-3230
    Keywords: encounter complexes ; 1-cyanonaphthalene ; norbornadiene ; stereospecific ; nucleophilic trapping ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Photo-induced electron donor-acceptor reactions between 1-cyanonaphthalene (CNN) and norbornadiene (N) generate products of several structure types. Methanol adducts (1-3) formed in polar solvents are rationalized via the radical cation, N+·, and stereospecific (exo-) nucleophilic attack by methanol. In less polar solvents, CNN and N form [2 + 2]-cycloadducts, exclusively on the exo-face of N. In non-polar solvents containing methanol, CNN, N and methanol combine to form 1:1:1 adducts, containing the sensitizer on the endo- and the methoxy groups on the exo-face. The formation of these products is rationalized via the trapping of encounter complexes of different geometries. Any rearrangement of the norbornenyl system can be eliminated, since neither tricyclyl nor 7-methoxynorbornenyl structures are formed. Apparently, the alcohol captures an endo-encounter complex of CNN and N by attack from the exo-face, similar to the attack of methanol on N+·. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 69
    Electronic Resource
    Electronic Resource
    Gain or loss of aromaticity in Diels-Alder transition states and adducts: a theoretical investigationThis paper was presented at the Satellite Meeting on Structural and Mechanistic Organic Chemistry: A Tribute to Norman L. Allinger, held in Athens, GA, USA, June 3-7, 1997. (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 133-140 
    Details
    ISSN: 0894-3230
    Keywords: aromaticity ; Diels-Alder transition states ; Diels-Alder adducts ; reaction mechanism ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Semiempirical, ab initio and DFT investigations on the mechanism of the Diels-Alder reactions of a set of masked dienes (ring-fused dienes), viz. o-quinodimethane, anthracene and α-vinylnaphthalene, with ethylene, and reactions of α-vinylnaphthalene with maleic anhydride and p-benzoquinone were performed with a view to understanding the role of masking factors on the activation and reaction energies. The reactions were found to occur in a concerted fashion through synchronous transition states (TSs) in the first two reactions and through asynchronous TS in the other case. Of the compounds studied, o-quinodimethane is the most reactive diene both in a kinetic and a thermodynamic sense. α-Vinylnaphthalene reacts faster with maleic anhydride than p-benzoquinone, as expected, and two possible stereoselective TSs, one endo and the other exo, have been located for the reactions of α-vinylnaphthalene with the above dienophiles. Calculations show that the relative gain or loss of aromatic stabilization of the benzonoid ring in the transition state and in the product seems to play a major role in the kinetic and thermodynamic control of these reactions. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 70
    Electronic Resource
    Electronic Resource
    Infrared spectra and conformation of methyl-substituted benzoic acidsPresented in part at the VIth International Conference on Correlation Analysis in Chemistry, Prague, 5-9 September 1994. (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 141-148 
    Details
    ISSN: 0894-3230
    Keywords: methylbenzoic acids ; infrared spectra ; conformation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Infrared spectra of all isomers of polymethyl-substituted benzoic acids were recorded in the carbonyl and hydroxyl regions in tetrachloromethane at various concentrations and interpreted in terms of conformation. According to a plot of ν(C=O) of the monomeric form vs Hammett substituent constants σ, these compounds may be classified into two classes. Derivatives with none or only one methyl group in the ortho position are concluded to exist in an equilibrium of two planar conformations, unless the equilibrium is degenerate. Derivatives with two ortho-situated methyl groups are concluded to take up one non-planar conformation. These findings are supported by the shape of the hydroxyl and carbonyl bands, which are unsymmetrical in the former class, although they could not be reliably separated into bands pertinent to the individual conformers. This conclusion is at variance with the common interpretation which has invariably ascribed to these and similar ortho derivatives non-planar conformations with a variable torsional angle. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 71
    Electronic Resource
    Electronic Resource
    Ab initio calculations on P - C bond cleavage in phosphoranyl radicals: implications for the biodegradation of organophosphonate derivatives (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 149-154 
    Details
    ISSN: 0894-3230
    Keywords: P - C bond cleavage ; phosphoranyl radicals ; organophosphonate biodegradation ; ab initio calculations ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Barrier heights for P - C bond homolysis in P-hydroxy-P-methyl-P,P-dioxophosphoranyl and P,P,P-trihydroxy-P-methylphosphoranyl were calculated using well correlated levels of electronic structure theory. The best estimate for the difference in barriers between the two indicates that homolysis is more facile for P,P,P-trihydroxy-P-methylphosphoranyl by roughly 9 kcal mol-1. This result suggests that bacterial pathways leading to P - C bond cleavage in organophosphonate derivatives will preferentially proceed via initial one-electron reduction of substrates rather than oxidation. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 72
    Electronic Resource
    Electronic Resource
    Mechanism of cycloaddition to indolizines (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 201-208 
    Details
    ISSN: 0894-3230
    Keywords: indolizines ; cycloaddition ; reaction mechanism ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The peculiarities of [8+2] cycloaddition reactions of indolizines with dienophiles are reviewed. Quantum chemical SINDO1, AM1 and ab initio calculations of transition states were performed for [8+2] cycloaddition reactions of indolizine and 6-nitroindolizine with a series of alkenes with donor and acceptor groups. The calculations predict a dipolar cycloaddition mechanism (electrophilic addition and ring closure) for reactions of indolizine and 6-nitroindolizine with nitroethylene. For the reaction of 6-nitroindolizine with N,N-dimethylaminoethylene, the predicted mechanism corresponds to a previously unknown ‘inverse’ dipolar cycloaddition (nucleophilic addition and ring closure). © 1998 John Wiley & Sons, Ltd.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 73
    Electronic Resource
    Electronic Resource
    Theoretical studies on the gas-phase nucleophilic substitution reactions of benzyl chlorides with phenoxides and thiophenoxides (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 115-124 
    Details
    ISSN: 0894-3230
    Keywords: cross-interaction constants ; gas-phase nucleophilic substitution reactions ; PM3 MO ; benzyl chlorides ; phenoxides ; thiophenoxides ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Gas-phase nucleophilic substitution reactions of Y-benzyl chlorides with X-phenoxide and X-thiophenoxide nucleophiles were investigated theoretically using the PM3 semi-empirical MO method. The Leffler-Grunwald rate-equilibrium and Brønsted correlations predict that the degree of bond formation in the transition state (TS) is approximately 45 and 40% on the reaction coordinate for the phenoxides and thiophenoxides, respectively. For a weaker nucleophile, a later TS is obtained with an increased bond making and breaking. The variation of the TS structure with substituents in the nucleophile is thermodynamically controlled and is well correlated by rate-equilibrium relationships. In contrast, the TS variation (a tighter TS) with substituent (for a stronger acceptor Y) in the substrate is dependent only on variations of the intrinsic barrier and so cannot be correlated by such thermodynamically based rate-equilibrium relationships. The gas phase ρX and ρY values are much greater in magnitude than those in solution. A similar gas-phase theoretical cross-interaction constant, ρXY (ca -0.60), is obtained for both phenoxides and thiophenoxides, which is in good agreement with the experimental value (-0.62) for the thiophenoxide reactions in MeOH at 20.0 °C. The oxy and sulfur anion bases lead to a similar TS structure, but a lower reactivity for the former is due to a greater endothermicity of the reaction. A relatively wide range variation of the reaction energies, ΔG°, can be ascribed to the loss of resonance stabilization of anion nucleophiles upon product formation. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 74
    Electronic Resource
    Electronic Resource
    Osmium(VIII)/ruthenium(III) catalysis of periodate oxidation of acetaldehyde in aqueous alkaline medium (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 171-176 
    Details
    ISSN: 0894-3230
    Keywords: acetaldehyde ; oxidation ; periodate ; osmium (VIII) catalysis ; ruthenium (III) catalysis ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Os(VIII) and Ru(III) catalysis of the periodate oxidation of acetaldehyde in aqueous alkaline medium was investigated. The catalytic efficiency is Ru(III)〈Os(VIII). The product of oxidation in both cases is acetate and IO3-. The stoichiometry is the same in both catalyzed reactions, i.e. [IO4-]:[CH3CHO] = 1:1. Probable mechanisms are proposed and discussed. The reaction constants involved in the mechanisms are derived. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 75
    Electronic Resource
    Electronic Resource
    Solvolysis of benzylic chlorides with extended charge delocalization. α-tert-butyl(2-naphthyl)methyl, 9-fluorenyl and monosubstituted benzhydryl chlorides (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 223-229 
    Details
    ISSN: 0894-3230
    Keywords: Solvolysis ; Grunwald-Winstein-type analysis ; Hammett-type analysis ; YxBnCl scale ; 1-aryl-1-phenylmethyl cations ; Mulliken population analysis ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Rate constants of solvolysis of α-tert-butyl(2-naphthyl)methyl chloride (1), 9-fluorenyl chloride (2) and a series of monosubstituted benzhydryl chlorides (3) in a wide range of solvents were measured. Grunwald-Winstein-type correlation analysis of log k for 2 and 3 against YBnCl, with or without nucleophilicity N, yielded less satisfactory linear correlations than that against log k(1). A new scale of solvent ionizing power, YxBnCl, for the correlation of solvolytic reactivities of benzylic chlorides with extended charge delocalization based on log k(1) was developed. Application to the mechanistic study suggested the solvolysis of 2 and 4-nitrobenzhydryl chloride were non-limiting. Hammett plots against σ+ constants exhibited more negative ρ values in less nucleophilic solvents. In a benzhydryl chloride containing a strong deactivating substituent, such as 4-nitro, the positive charge delocalizes mainly over the unsubstituted ring in the cationic transition state. The uneven charge distribution was also confirmed by Mulliken population analysis at the level of the RHF/6-31G*//RHF/3-21G(*) basis set for cations. Comparison of the results of correlation analysis using the equation log(k/k0) = mY vs the equation log(k/k0) = mY+hI, and using the equation log(k/k0) = mY+lN vs the equation log(k/k0) = mY+lN+hI indicated the use of YBnCl or YxBnCl could give a better understanding of solvolytic mechanisms than the combinatorial use of YCl and I. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 76
    Electronic Resource
    Electronic Resource
    Empirical treatment of solvent-solute interactions: medium effects on the electronic absorption spectrum of β-carotene (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 193-200 
    Details
    ISSN: 0894-3230
    Keywords: Solvent-solute interactions ; β-carotene ; electronic absorption spectrum ; solvent effects ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solvent effects on the wavenumber of the maximum of the longest wavelength electronic absorption band of all-trans-β-carotene were determined in 34 solvents. Together with results from previous studies, a data set for 51 solvents, mostly non-hydrogen bond donors, was constructed. This information was analyzed in terms of reaction field models and also showed its value for correlation purposes when used either alone or in combination with standard empirical solvent polarity-polarizability scales. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 77
    Electronic Resource
    Electronic Resource
    Theoretical study on pyrolysis and sensitivity of energetic compounds. Part 4. Nitro derivatives of phenols (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 177-184 
    Details
    ISSN: 0894-3230
    Keywords: nitro derivatives of phenols ; pyrolysis initiation reactions ; impact sensitivity ; UHF-SCF-AM1 MO method ; activation energy. ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The UHF-SCF-AM1 MO method was applied to the study of two kinds of pyrolysis reactions of six nitro derivatives of phenols (homolysis reaction by rupture of the C - NO2 bond into radicals and isomerization reaction involving phenolic hydrogen transferring to oxygen on the NO2 group). The molecular geometries of reactants, transition states and products were fully optimized. The potential energy curves and activation energies were first obtained. The results show that this category of compounds is more easily initiated via isomerization reactions than by homolysis reactions. The parallel relationship among the Wiberg bond order of the pyrolysis-initiation H - O bond in the molecule of a reactant, the activation energy of the isomerization reaction breaking the H - O bond and impact sensitivity of the reactant gives ‘the principle of the smallest bond order’ (PSBO) powerful support. The sensitizing effect of a phenol group was elucidated based on calculation results. The different influences of OH and NO2 groups on the heat of formation of a molecule are discussed. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 78
    Electronic Resource
    Electronic Resource
    Unexpected rate enhancement in the intramolecular carboxylic acid-catalyzed cleavage of o-carboxybenzohydroxamic acid (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 216-222 
    Details
    ISSN: 0894-3230
    Keywords: o-carboxybenzohydroxamic acid ; phthalic anhydride ; phthalic acid ; hydrolysis ; intramolecular acid catalysis ; kinetics ; activation parameters ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Phthalic anhydride was detected spectrophotometrically in the hydrolysis of o-carboxybenzohydroxamic acid (OCBA) in CH3CN-H2O solvent containing 0.03 mol dm-3 HCl. Pseudo-first-order rate constants (k1) for hydrolysis of OCBA are almost independent of the change in CH3CN content from 10 to 80% (v/v) in mixed aqueous solvents. The rate constants k1 are more than 10-fold larger than the corresponding rate constants for hydrolysis of phthalamic acid. These observations are explained in terms of a mechanism slightly different from the mechanism for hydrolysis of phthalamic acid. The activation parameters, ΔH* and ΔS*, are not affected appreciably by an increase in CH3CN content from 10 to 80% in mixed aqueous solvents. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 79
    Electronic Resource
    Electronic Resource
    Solute-solvent and solvent-solvent interactions in binary solvent mixtures. Part 7. Comparison of the enhancement of the water structure in alcohol-water mixtures measured by solvatochromic indicators (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 185-192 
    Details
    ISSN: 0894-3230
    Keywords: solute-solvent interactions ; solvent-solvent interactions ; binary solvents ; alcohol-water mixtures ; water structure ; solvatochromic indicators ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A preferential solvation model that takes into account the enhancement of the structure of water when small amounts of alcohol are added was applied to solvatochromic data for binary mixtures of water with 2-methylpropan-2-ol, propan-2-ol, ethanol and methanol. Application of the model allows the calculation of the effect of the enhancement of the water structure on solvatochromic solvent properties. It is demonstrated that the enhancement of water structure increases the solvent dipolarity/polarizability and hydrogen-bond donor acidity and decreases the solvent hydrogen-bond acceptor basicity. The effect decreases in the order 2-methylpropan-2-ol-water, propan-2-ol-water, ethanol-water and methanol-water. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 80
    Electronic Resource
    Electronic Resource
    Structural dependence of heterolytic bond dissociation energy of carbon-carbon σ bonds in hydrocarbons (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 157-170 
    Details
    ISSN: 0894-3230
    Keywords: heterolytic bond dissociation energy ; carbon-carbon σ bonds ; hydrocarbons ; structural dependence ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The coordination of a resonance-stabilized hydrocarbon cation and anion yielded a series of unprecedented hydrocarbons, which are susceptible to thermal heterolytic cleavage of carbon-carbon σ bonds in polar media, generating the original ions under reversible conditions. When the component ions were sufficiently stabilized, some ion pairs were even isolated as solids, thus providing the first examples of hydrocarbon salts. The direct observation of the heterolysis by means of spectroscopy permitted reliable thermodynamic treatments of the observed degree of ionic dissociation. Correlation of the free energy of heterolysis with solvent dielectric constants and parameters of ion stabilities such as pKHA, pKR+ and redox potentials revealed the importance of the thermodynamic stabilities of ions, the degree of solvation and steric congestion in the starting molecule as major controlling factors in the heterolysis. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 81
    Electronic Resource
    Electronic Resource
    Correlation of the rates of solvolysis of the N,N-diphenylcarbamoylpyridinium ion (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 273-276 
    Details
    ISSN: 0894-3230
    Keywords: N,N-diphenylcarbamoylpyridinium ion ; solvolysis ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solvolyses of the N,N-diphenylcarbamoylpyridinium ion are subject to specific and/or general base catalysis, which can be eliminated by addition of perchloric acid or increased, especially in fluoroalcohol-containing solvents, by addition of pyridine. The uncatalyzed solvolyses in aqueous methanol and aqueous ethanol involve a weakly nucleophilically assisted (l  =  0.22) heterolysis and the solvolyses in the pure alcohols are anomalously slow. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 82
    Electronic Resource
    Electronic Resource
    Effects of ionic and non-ionic micelles on rate of hydroxide ion-catalyzed hydrolysis of securinine (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 209-215 
    Details
    ISSN: 0894-3230
    Keywords: securinine ; cationic micelles ; anionic micelle ; non-ionic micelle ; alkaline hydrolysis ; kinetics ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effects of micelles of cetyltrimethylammonium bromide (CTABr), tetradecyltrimethylammonium bromide (TTABr), sodium dodecyl sulfate (SDS) and polyoxyethylene 10 lauryl ether (C12E10) on the rates of alkaline hydrolysis of securinine were studied at a constant [-OH] (0.05 M). An increase in the total concentrations of CTABr, TTABr, SDS and C12E10 from 0.0 to 0.2 M causes a decrease in the observed pseudo-first-order rate constants (kobs) by factors of ca 2.5, 3, 7 and 4, respectively. The observed data are explained in terms of pseudophase and pseudophase ion-exchange (PIE) models of micelle. The binding constants, KS, of securinine with SDS, C12E10, CTABr and TTABr micelles are 32.4, 14.8, 22.1, and 9.1 M-1, respectively. The magnitudes of the second-order rate constants, kM, for the reactions in the micellar pseudophase are negligible compared with the corresponding rate constant, kW, for the reaction occurring in the aqueous pseudophase for CTABr, TTABr, SDS and C12E10. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 83
    Electronic Resource
    Electronic Resource
    Colloidal CdS-induced photocatalytic reaction of 2-methylindole - mechanistic analysis of oxidation of indoles (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 277-282 
    Details
    ISSN: 0894-3230
    Keywords: colloidal CdS-induced photochemical reactions ; photocatalytic reactions ; photooxidation ; 2-methylindole ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 2-Methylindole (2-MI) is adsorbed on the surface of colloidal CdS particles with an adsorption intensity of 0.6 × 103 dm3 mol-1. A new emission band at 530 nm is produced by forming an exciplex between excited CdS and 2-MI and the red emission due to CdS is simultaneously quenched. The emission maxima of green bands for different indoles increase in the order indole 〈 tryptophan 〈 2-MI 〈 3-MI and are observed at 508, 520, 530 and 540 nm, respectively. The shift in emission maxima is related to the oxidation potential of these substrates. The irradiation of an aerated reaction mixture containing CdS and 2-MI with visible light induces the oxidation of adsorbed 2-MI by photogenerated holes to produce 2-methyl-3-indolinone and 2-acetamidobenzaldehyde. The latter product is formed due to oxidative C - C bond cleavage of the pyrrole ring. The reactivity of trapped holes towards the adsorbed 2-MI is evidenced by a decrease in the lifetime of the red emission of CdS in the presence of 2-MI. In this reaction the possibility of the participation of singlet oxygen is ruled out. A general mechanism of CdS-induced oxidation of indoles is discussed. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 84
    Electronic Resource
    Electronic Resource
    Conformational analysis of a 12-membered crown dithioether in the solid state and in solution (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 241-253 
    Details
    ISSN: 0894-3230
    Keywords: crown dithioether ; conformational analysis ; multicomponent equilibrium ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The solid-state molecular structure and the conformational behaviour in solution of the 12-membered crown dithioether 8-methyl-1,4-dioxa-7,10-dithiacyclododecane-5,12-dione were studied by x-ray crystallography, 1H and 13C NMR spectroscopy and molecular mechanics. The conformational rigidity of some constituent structural fragments allowed a detailed analysis of the structure and distribution of the conformers. A protocol for studies of multiconformational equilibrium was developed by means of the combined use of structure calculations and dynamic NMR measurements. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 85
    Electronic Resource
    Electronic Resource
    Metal-catalyzed carbenoid reactions with iodonium and sulfonium ylides (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 321-333 
    Details
    ISSN: 0894-3230
    Keywords: metal-catalyzed carbenoid reactions ; iodonium ylides ; sulfonium ylides ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Transition metal-catalyzed decomposition of phenyliodonium and diphenylsulfonium ylides was investigated with regard to application in asymmetric carbenoid reactions. Phenyliodonium ylides react in the presence of Rh(II) catalysts with the same selectivity in inter- and intramolecular cyclopropanations as the corresponding diazo compounds, and intramolecular CH insertions proceed with identical enantioselectivities. With diphenylsulfonium ethoxycarbonylmethylide the Cu(I)-catalyzed cyclopropanation of olefins affords trans/cis ratios and asymmetric inductions identical with those of diazo compounds, but with Rh(II) catalysts some small, although significant, selectivity variations occur, which are ascribed to coordination of diphenyl sulfide to one of the coordination sites of the catalyst. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 86
    Electronic Resource
    Electronic Resource
    Principles of physical organic chemistry for molecular architecture and functions (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 299-304 
    Details
    ISSN: 0894-3230
    Keywords: molecular architecture ; molecule-based magnets ; biopolymers ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Application of the principles of physical organic chemistry to the construction of molecule-based magnets is discussed. Not only the magnetic structures of conventional magnets but also secondary and tertiary structures of biopolymers are instrumental in the molecular design. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 87
    Electronic Resource
    Electronic Resource
    Studies of reactive intermediates using matrix and gas-phase techniques (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 350-355 
    Details
    ISSN: 0894-3230
    Keywords: 1,3-dipoles ; cumulenes ; infrared spectroscopy ; mass spectrometry ; flash vacuum thermolysis ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In the direct investigation of reactive intermediates it is particularly valuable to use a combination of several spectroscopic techniques. This commentary highlights recent examples, using primarily flash vacuum thermolysis for the generation of the intermediates, and matrix IR spectroscopy in conjunction with gas-phase mass spectrometric methods for their identification. The examples include nitrile imines, nitrile ylides, nitrile sulfides and selenides, dinitrogen sulfide and several novel cumulenes (X=C=C=Y, RN=C=C=C=X). © 1998 John Wiley & Sons, Ltd.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 88
    Electronic Resource
    Electronic Resource
    Non-cross-linked and cross-linked poly(alkylmethyldiallylammonium halides): synthesis and aggregation behavior (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 305-320 
    Details
    ISSN: 0894-3230
    Keywords: poly(alkylmethyldiallylammonium halides) ; aggregation behavior ; polyelectrolytes ; polysoaps ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Hydrophobically modified polyelectrolytes (polysoaps) are a unique class of water-soluble polymers containing distinct hydrophobic and hydrophilic regions. Above a certain concentration, polysoaps form intramolecular and intermolecular aggregates in aqueous solution. They have attracted much attention not only for their ability to mimic some functions demonstrated by biopolymers but also for their important industrial applications. This review highlights some interesting features of novel non-cross-linked and cross-linked poly(alkylmethyldiallylammonium halides) that have been described in recent years. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 89
    Electronic Resource
    Electronic Resource
    Is the brain ready for physical organic chemistry? (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 334-340 
    Details
    ISSN: 0894-3230
    Keywords: brain chemistry ; membrane proteins ; molecular neurobiology ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Efforts to developed detailed insights into the structure and function of the molecules of memory, thought and sensory perception - physical organic chemistry on the brain - are described. By combining more conventional chemical tools with a number of techniques adapted from modern biology, it is now possible to perform systematic structure-function studies on the integral membrane proteins that play a central role in molecular neurobiology. There are substantial challenges associated with such studies, but we believe the potential payoff is considerable. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 90
    Electronic Resource
    Electronic Resource
    Vicarious nucleophilic substitution of hydrogen. Mechanism and orientation (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 341-349 
    Details
    ISSN: 0894-3230
    Keywords: vicarious nucleophilic substitution ; hydrogen ; mechanism ; orientation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Hydrogens located at activated positions in electrophilic arenes, e.g. ortho and para hydrogens in nitrobenzenes, can be replaced with a nucleophile moiety provided there is at least one nucleofuge X connected to the nucleophilic centre. As the group really leaving in this hydrogen substitution process is not the hydride anion but X, the reaction has been named vicarious nucleophilic substitution of hydrogen (VNS). The concepts on the mechanism of the reaction and their experimental background are presented. Reactivity and orientation - the fundamental questions concerning synthetical applications of VNS - are discussed in light of the supposed mechanistic picture.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 91
    Electronic Resource
    Electronic Resource
    Preface (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 291-291 
    Details
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No Abstract
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 92
    Electronic Resource
    Electronic Resource
    Unusual reactivity of highly strained cyclophanesDedicated to Prof. Dr Maitland Jones, Jr, on the occasion of his 60th birthday (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 362-376 
    Details
    ISSN: 0894-3230
    Keywords: highly strained cyclophanes ; reactivity ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An essential feature of the concept of aromaticity has been the stability and lack of reactivity of aromatics relative to that of other unsaturated compounds. Contrary to this general experience, high and unusual reactivity is encountered when simple, monocyclic benzene rings are bent by short bridges into a boat-shaped conformation, as is the case in small [n] paracyclophanes (n ≤ 8) and [n]metacyclophanes (n ≤ 7). This is illustrated, mostly with examples taken from the authors' own work, for thermal and photochemical behavior and reactions with electrophiles, nucleophiles and dienophiles. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 93
    Electronic Resource
    Electronic Resource
    Heterogeneous catalysis of organic reactions (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 356-361 
    Details
    ISSN: 0894-3230
    Keywords: heterogeneous catalysis ; organic reactions ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A decade's worth of work is reviewed: building on the demonstrated prowess of heterogeneous catalysis in industrial organic chemistry, the author's laboratory devised efficient catalysts for a number of organic reactions, based on aluminosilicates such as clays and zeolites. This review also spells out, at a time when creative research is overshadowed by imitative research, some of the methodological musts that also happen to characterize physical organic chemistry: the devising of experiments so that accurate numerical data can be obtained; the importance of remote, interdisciplinary connections; the need for estrangement from stereotypic preconceptions that may obscure the true explanations for the phenomena; and the over-riding need for concerning oneself only, or at least predominantly, with the important facts that nature tells, if one cares to listen. © 1998 John Wiley & Sons, Ltd.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 94
    Electronic Resource
    Electronic Resource
    Flash photolytic generation and investigation of short-lived reaction intermediates: a case study (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 292-298 
    Details
    ISSN: 0894-3230
    Keywords: flash-photolysis ; short-lived reaction intermediates ; mandelic acid ; keto-enol tautomers ; enzyme-catalyzed racemization ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The advantage of adding more structure-diagnostic information to the simple detection of flash photolytically generated transient species by changes in UV-visible light absorbance is illustrated by a case study involving the mandelic acid keto-enol system. An early report based on preliminary evidence proposed that flash photolysis of phenyldiazoacetic acid produces the enol of mandelic acid by hydration of phenylhydroxyketene, itself generated by a photo-Wolff reaction of the diazo acid. Further examination, however, shows that this is only a minor route, and that the major pathway is a new enol-forming reaction involving what appears to be hydration of a carboxycarbene formed by dediazotization of the diazo compound. Hydration of phenylhydroxyketene is nevertheless the reaction by which mandelic acid enol is generated when esters of benzoylformic acid are the flash photolysis substrates. These mechanisms, and also identification of the enol as a tranisent species, are supported by detailed arguments involving acid-base catalysis, solvent isotope effects, and the use of oxygen-18 as a tracer. The work produces a keto-enol equilibrium constant for the mandelic acid system, pKE  =  16.19, and also acidity constants of the enol ionizing as an oxygen acid, pKEa  =  6.39, and the keto isomer ionizing as a carbon acid, pKKa  =  22.57. The bearing of these results on the enzyme-catalyzed racemization of mandelic acid is discussed. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 95
    Electronic Resource
    Electronic Resource
    A new way of analyzing vibrational spectra. I. Derivation of adiabatic internal modes (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 67 (1998), S. 1-9 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new way of analyzing measured or calculated vibrational spectra in terms of internal vibrational modes associated with the internal parameters used to describe geometry and conformation of a molecule is described. The internal modes are determined by solving the Euler-Lagrange equations for molecular fragments φn described by internal parameters ζn. An internal mode is localized in a molecular fragment by describing the rest of the molecule as a collection of massless points that just define molecular geometry. Alternatively, one can consider the new fragment motions as motions that are obtained after relaxing all parts of the vibrating molecule but the fragment under consideration. Because of this property, the internal modes are called adiabatic internal modes, and the associated force constants ka, adiabatic force constants. Minimization of the kinetic energy of the vibrating fragment φn yields the adiabatic mass ma (corresponding to 1/Gnn of Wilson's G matrix) and, by this, adiabatic frequencies ωa. Adiabatic modes are perfectly suited to analyze and understand the vibrational spectra of a molecule in terms of internal parameter modes in the same way as one understands molecular geometry in terms of internal coordinates.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 1-9, 1998
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 96
    Electronic Resource
    Electronic Resource
    Adiabatic evolution of eigenspectra of model 1-D and 2-D Hamiltonians: Quantum adiabatic switching algorithm in a time-independent Fourier grid Hamiltonian framework (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 67 (1998), S. 133-141 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We explore the viability of a time-independent quantum adiabatic switching algorithm in the Fourier grid Hamiltonian (FGH) framework in the presence of degeneracy, avoided crossing, and chaos. The algorithm is simple and cost effective and provides information about the full eigenspectrum of the evolving Hamiltonian. It is shown to be capable of capturing accurately the change in the pattern of level spacing distribution statistics as one switches from a nonchaotic region of parameter values into the chaotic region. The Transition turns out to be less sharp than anticipated.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 133-141, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 97
    Electronic Resource
    Electronic Resource
    Cyanide adsorbed on coinage metal electrodes: A relativistic density functional investigation (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 67 (1998), S. 175-185 
    Details
    ISSN: 0020-7608
    Keywords: potential dependence ; vibrational frequency ; coinage metal electrodes ; relativistic effects ; density functional calculation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The adsorptive properties of cyanide (CN-) on coinage metal (M) electrodes (M=Cu, Ag, Au) have been investigated using a relativistic density functional method. The way to model the electrochemical potential applied to the electrodes is to consider the systems in the presence of a perturbative external field F. The field-perturbative approach is proven to be a suitable method in interpreting the observed spectral shifts with electrode potential. The calculated potential-dependent shifts of ωM(SINGLE BOND)CN and ωC(SINGLE BOND)M are similar for the three metals, in agreement with experiment observations. The relativistic effects are required to account for the similarity in the frequency shifts of ωM(SINGLE BOND)CN. The calculated vibrational tuning rates dωC(SINGLE BOND)N/dF are 6.61×10-7, 6.61×10-7, and 5.64×10-7 cm-1/(V/cm) for M=Cu, Ag, and Au, respectively. The coupling of the M(SINGLE BOND)CN and C(SINGLE BOND)N internal modes contributes significantly (about 25%) to the size of the frequency shifts ΔωC(SINGLE BOND)N of the ligand. The effect of electric fields on the metal(SINGLE BOND)CN- bonding is also investigated. It is shown that changes in the magnitude of CN- to the metal donation and M(SINGLE BOND)CN bond strength occur under the influence of the electric field.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 175-185, 1998
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 98
    Electronic Resource
    Electronic Resource
    Model study of the impact of orbital choice on the accuracy of coupled-cluster energies. I. Single-reference-state formulation (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 67 (1998), S. 205-219 
    Details
    ISSN: 0020-7608
    Keywords: coupled-cluster theory ; electron correlation effects ; molecular orbital choice ; reference determinant choice ; quasi-degenerate states ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The impact of the choice of molecular orbital sets on the results of single-reference-state coupled-cluster (CC) methods was studied for the H4 model. This model offers a straightforward way of taking into account all possible symmetry-adapted orbitals. Moreover, the degree of quasi-degeneracy of its ground state can be varied over a wide range by changing its geometry. The CCD, CCSD, and CCSDT approaches are considered. Surfaces representing the dependence of the energy on the parameters defining the orbitals are obtained. It is documented that for every method there exist alternative orbital sets which allow one to obtain more accurate energies than the standard (HF, BO, and NO) ones. However, for many of the former orbital sets, one obtains relatively large one-body amplitudes or one may encounter problems with solving the CC equations by conventional methods. An interesting variety of orbitals which might be useful for studies of quasi-degenerate states by the CCD method was found.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 205-219, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 99
    Electronic Resource
    Electronic Resource
    Model study of the impact of orbital choice on the accuracy of coupled-cluster energies. III. State-universal coupled-cluster method (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 67 (1998), S. 239-250 
    Details
    ISSN: 0020-7608
    Keywords: coupled-cluster theory ; electron correlation effects ; molecular orbital choice ; reference determinant choice ; quasi-degenerate states ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Model studies of the impact of the choice of molecular orbital sets on the accuracy of the results of the state-universal coupled-cluster method involving one- and two-body excitations (SU-CCSD) were performed for the H4 model, which offers a straightforward way of representing any symmetry-adapted orbitals as well as the possibility of varying over a wide range the degree of quasi-degeneracy of a state. Energies of the three lowest 1A1 states obtained for 13 sets of standard quantum chemical orbitals as well as for a vast variety of nonstandard orbital sets defined by nodes of a two-dimensional grid are compared. It is shown that there exist nonstandard orbital sets that allow one to obtain more accurate energies than the standard orbital sets. It is also demonstrated that the recently defined [K. Jankowski et al., Int. J. Quantum Chem. 67, 221 (1998)] maximum proximity orbitals (MPO) yield more accurate results than any other of the commonly applied orbital sets. These orbitals are especially effective outside the strong-quasi-degeneracy region.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 239-250, 1998
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 100
    Electronic Resource
    Electronic Resource
    Erratum: Conformational analysis of polypeptide chains with the aid of density of states calculations (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 67 (1998), S. 341-341 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...