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  • 1
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    Quantification of bone surface textures: exploring a new method of ontogenetic ageing (2023)
    In:  Journal of Analytical Science and Technology vol. 14 no. 1
    Details
    Publication Date: 2024-02-26
    Description: Identifcation of ontogenetic age classes plays an important role in the felds of zoology, palaeontology and archaeology, where accurate age classifcations of (sub)fossil remains are a crucial component for the reconstruction \nof past life. Textural ageing\xe2\x80\x94the identifcation of age-related bone surface textures\xe2\x80\x94provides a size-independent \nmethod for age assessment of vertebrate material. However, most of the work so far is limited to qualitative results. \nWhile qualitative approaches provide helpful insights on textural ageing patterns, they are heavily subject to observer \nbias and fall short of quantitative data relevant for detailed statistical analyses and cross-comparisons. Here, we present a pilot study on the application of 3D surface digital microscopy to quantify bone surface textures on the long \nbones of the grey heron (Ardea cinerea) and the Canada goose (Branta canadensis) using internationally verifed \nroughness parameters. Using a standardised measuring protocol, computed roughness values show a strong correlation with qualitative descriptions of textural patterns. Overall, higher roughness values correspond to increased numbers of grooves and pits and vice versa. Most of the roughness parameters allowed distinguishing between diferent \nontogenetic classes and closely followed the typical sigmoidal animal growth curve. Our results show that bone \ntexture quantifcation is a feasible approach to identifying ontogenetic age classes.
    Keywords: General Physics and Astronomy ; General Environmental Science ; General Biochemistry ; Genetics and Molecular Biology ; General Materials Science ; General Chemistry ; Roughness ; Surfaces ; Taphonomy ; Topography ; Bone ; Ontogeny ; Digital microscopy
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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  • 2
    Electronic Resource
    Electronic Resource
    Self-Assembly of Bisurea Compounds in Organic Solvents and on Solid Substrates (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1238-1243 
    Details
    ISSN: 0947-6539
    Keywords: gels ; electron microscopy ; scanning tunneling microscopy ; self-assembly ; ureas ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New low molecular weight gelators based on the structure R—NHCONH—X—NHCONH—R have been synthesized and tested for their ability to cause gelation of organic solvents. Compounds 2 (R = n-dodecyl, X = -(CH2)9-), 3 (R = n-dodecyl, X = -(CH2)12-), 4 (R = n-dodecyl, X = 4, 4′-biphenyl), and 5 (R = benzyl, X = -(CH2)9-) form thermoreversible gels with a wide range of organic solvents, at concentrations well below 10 mgmL-1. Depending on the nature of the R and X groups, the solvents that undergo gelation include hexadecane, p-xylene, 1-octanol, n-butyl actetate, cyclohexanone, and tetralin. The gels are stable up to temperatures well above 100°C, but are easily disrupted by mechanical agitation. Light microscopic investigations revealed that compounds 2-5 spontaneously aggregate to form thin flat fibers, which can be several hundreds of micrometers long and only 2-10 μm wide. Depending on the solvent, multiple twists in the fibers are observed. In the gels, these fibers form an extended three-dimensional network, which is stabilized by multiple mechanical contacts between the fibers. Electron microscopy and X-ray powder diffraction revealed that the fibers consist of stacks of sheets. The thickness of the sheets is 3.65 and 3.85 nm for 2 and 3, respectively. Scanning tunneling microscopic investigations of 2 absorbed on graphite showed that 2 forms long ribbons with a width of 5.0 nm. In the ribbons the molecules have a parallel arrangement, with the long molecular axis perpendicular to the long ribbon axis. The two urea groups within a given molecule are each part of mutually parallel extended chains of hydrogen bonds. Based on these observations a model is proposed for the arrangement of the molecules in the fibers. In this model the bisurea molecules aggregate through hydrogen-bond formation into long ribbons, which assemble into sheets. In these sheets the ribbons are tilted. Finally, the sheets stack to form long thin fibers. This model is supported by molecular dynamics simulations.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030811
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  • 3
    Electronic Resource
    Electronic Resource
    Tripodal Synthetic Peptide BundlesDedicated to Professor Wolfgang Beck on the occasion of his 65th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1254-1268 
    Details
    ISSN: 0947-6539
    Keywords: peptide bundles ; peptides ; pseudo-peptides ; template synthesis ; tripodal ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stereochemical course of the formation of the two diastereomers of trimethyl 2,2′,2″-nitrilotris[2-(benzoylamino)acetate], 2a and 2b, is described. The structures of both isomers were confirmed by X-ray diffraction studies. Diastereomer 2b could be obtained in larger quantities by epimerisation of 2 a to 2 b with catalytical amounts of NaOMe. The (RRR/SSS)-triester 2 b is a suitable template for the synthesis of tripodal peptide bundles. Saponification of 2 b yielded the C3-symmetrical racemic triacid 4 b, which was coupled with amino acid methyl esters and dipeptide esters to give pseudo-hexapeptides and pseudo-nonapeptides, respectively. The resulting mixtures of diastereomers were easily separated by crystallisation. Their absolute configuration at the template unit (RRR or SSS) was established by means of the CD spectra. The pseudo-hexapeptide (SSS)N(BzGly*ValOMe)3 (14) was saponified to yield the optically pure triacid (SSS)N(BzGly*ValOH)3 (23). Compound 23 is an ideally preorganised template for the production of longer tripodal peptides. This was illustrated by the synthesis of two pseudo-pentadecapeptides. Peptide bundles with polar side chains (histidine and serine) or end groups (catechol or hydroxamate units) were synthesised by using the templates 4 b, 22 and 23 as anchors.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030813
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  • 4
    Electronic Resource
    Electronic Resource
    Noncovalent Assembly of Functional Groups on Calix[4]Arene Molecular Boxes (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1823-1832 
    Details
    ISSN: 0947-6539
    Keywords: calixarenes ; hydrogen bonds ; molecular boxes ; noncovalent assembly ; supramolecular chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Calix[4]arenes diametrically substituted at the upper rim with two melamine units spontaneously form well-defined box-like assemblies in the presence of two equivalents of 5,5-diethylbarbituric acid. These assemblies, consisting of nine different components, are held together by 36 hydrogen bonds and are stable in apolar solvents at concentrations of up to 10-4M. This paper reports the first X-ray crystal structure, and the MALDI TOF mass spectra together with the complete 1H NMR spectroscopic characterization of these hydrogen-bonded assemblies. The crystal structure clearly shows that the assemblies are stereogenic, as a result of the antiparallel orientation of the two rosette motifs. Furthermore, the synthesis of twelve new 1,3-bis(melamine)calix[4]arenes carrying different numbers and types of functionalities at the upper rim is described. Detailed 1H NMR spectroscopic studies on the assembly behavior of these functionalized calix[4]arenes shows that 1) polar substituents (e.g. nitro, cyano) hardly affect the stability of the hydrogen-bonded assembly; 2) hydrogen bond donating or accepting groups, like amino and acetamido, can disturb assembly of the boxes under certain conditions by destabilizing the calix[4]arene pinched cone conformation as a result of intramolecular hydrogen bond formation; and 3) sterically bulky groups (e.g. tBu) can significantly inhibit the formation of the hydrogen-bonded assembly, but this effect very much depends on the exact positions of the groups.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031115
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  • 5
    Electronic Resource
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    Zinc(II)-Catalyzed Disproportionation in Rubber: The mechanism of Sulfur Vulcanization Revisited (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1846-1851 
    Details
    ISSN: 0947-6539
    Keywords: disproportionations ; dithiocarba-mate ; homogeneous catalysis ; vulcanization ; zinc ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Model studies have shown that cross-link precursors, that is, intermediates in the sulfur vulcanization of rubber, are transformed into cross-links by a nonsymmetric but regioselective disproportionation mechanism. Thus, two equivalents of the crosslink precursor of the type R—S—S—X are transformed into X—S—X and the actual cross-link R—S—S—S—R. Exchange of sulfur atoms is a prerequisite. A mechanism involving an SNi′ reaction with an allylic moiety, suggested in the literature, has not been observed. The disproportionation reaction is catalyzed by rubber-soluble zinc-dithiocarbamate complexes, an important class of vulcanization accelerators. By virtue of ligand-functional-group exchange reactions these complexes serve to transport and exchange sulfur atoms.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031117
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  • 6
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    A Quintupled Superstructure of the KHg2 Type Realized for the New Stannide EuAuSn (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1852-1859 
    Details
    ISSN: 0947-6539
    Keywords: conductivity ; europium ; gold ; magnetic properties ; superstructures ; tin ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compound was prepared from the elements by reaction in a sealed tantalum tube at 1320 K followed by slow cooling to 970 K. EuAuSn crystallizes with a pronounced subcell of space group Imma (KHg2 type). Additional very weak reflections required a quintupled b axis. The superstructure was refined from single-crystal four-circle diffractometer data (Imm 2, a = 479.1(1) pm, b = 3833.6(5) pm, c = 820.1(1) pm, Z = 20, wR2 = 0.0834, 3675 F2 values and 94 variables). Six crystallographically different europium sites occur in the superstructure. Each europium site has an ordered near-neighbour environment of six gold and six tin atoms in the form of two tilted hexagons. Magnetic susceptibility measurements show Curie-Weiss behaviour above 50 K with an experimental magnetic moment of 7.6(1) μB/Eu, indicating divalent europium. EuAuSn orders antiferromagnetically at about 12 K and undergoes a metamagnetic transition at a critical field of 2.0(2) T. Electrical conductivity measurements show metallic behaviour with a room temperature value of 260 μΩcm. 151Eu and 119Sn Mössbauer spectroscopic experiments are compatible with divalent europium and show complex magnetic hyperfine field splitting at low temperature.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031118
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  • 7
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    Electronic and Geometrical Structures of Dialuminoxane, Diboroxane, and Their Sulfur Analogues: Ab Initio Study of H2X-Y-XH2 (X = Al, B; Y = O, S) Compounds (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1860-1865 
    Details
    ISSN: 0947-6539
    Keywords: ab initio calculations ; aluminum ; boron ; pi interactions ; sulfur ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structures of H2X—Y—XH2 compounds (X = B, Al; Y = O, S) have been studied by means of ab initio calculations at the MP4/6-311 G**/MP2/6-311G** level. The potential energy surface (PES) of the aluminoxane species H2Al—O—AlH2 is rather flat: the energy differences between the various located extrema are less than 1.5 kcal mol-1, and this shows that the observed geometrical preference is not due to electronic factors. For the sulfur analogues H2X—S—XH2 (X = B, Al), three minima are located on the PES: a planar C2v structure, a Cs structure in which one hydrogen atom bridges the two X atoms, and a C2v structure with two bridging hydrogen atoms. For H2Al—S—AlH2, the Cs structure is the most stable, and the planar C2v and the dibridged structures lie 3.2 and 6.7 kcal mol-1 higher, respectively. Qualitatively similar results are obtained for H2B—S—BH2: the Cs and planar C2v structures are nearly isoenergetic, and the dibridged minimum lies 19.4 kcal mol-1 above the planar C2v minimum. These results are rationalized by analyzing the ability of these systems to bend, depending on the nature (oxygen or sulfur) of the central Y atom. The conjugation in these species is also discussed, and calculations on model systems H2X—YH (X = B, Al; Y = O, S) are presented.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970031119
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  • 8
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    Stoichiometric and Catalytic Reactions of the Polysiloxane-Bound (Ether-Phosphine)Rhodium(I) Complex [ClRh(PO)(P ∼ O)] in InterphasesSupported organometallic complexes part 14. Part 13: E. Lindner, A. Jäger, F. Auer, W. Wielandt, P. Wegner, J. Mol. Catal. in press.Dedicated to Professor H. D. Kaesz on the occasion of his 65th birthdayNotation used in this paper: Fn = functionality; D, T, and Q denote alkoxysilanes with two, three, and four Si-O bonds, respectively; the superscript denotes the number of Si—O—Si bonds formed during the sol-gel process and is a measure of cross-linkage; for example, T0 = MeSi(OMe)3. P∼O: η1-P-coordinated ether-phosphine ligand; PO: η2-O,P-chelating ether-phosphine ligand. Cy = cyclohexyl, COE = cyclooctene, Py = pyridine. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1833-1845 
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    ISSN: 0947-6539
    Keywords: immobilized catalysts ; polysiloxanes ; P ligands ; rhodium ; sol-gel processes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of four equivalents of the monomeric trimethoxysilyl(T)-functionalized ether-phosphine ligand CyP(CH2CH2OCH3)(CH2)3SiR3 (R = OMe [1 a(T0)], Me [1 b]) with [{μ-ClRh(COE)2}2] yielded the monomeric pseudo 14 electron rhodium(I) complexes [ClRh(PO)(P∼O)] (2a(T0)2, 2 b). For the sol-gel process the complex 2 a(T0)2 was protected by introduction of the volatile, reversibly binding ligand pyridine. Thus, the monomeric compound 2 a(T0)2 was co-condensed with two and eight equivalents of the co-condensation agent MeSi(OMe)2(CH2)6(MeO)2SiMe (D0-C6-D0) to give the polysiloxane-bound congeners 2(Tn)2(Di-C6-Di)y (y = 2 and 8, respectively; i = 0-2; n = 0-3). The polysiloxane-bound complex 2(Tn)2-(Di-C6-Di)2 was treated with a variety of small molecules in the gas/solid and liquid/solid interphases. It was shown that a facile cleavage of the Rh-O bond in the ether-phosphine chelate occurred even in the solid state. The reaction of 2(Tn)2-(Di-C6-Di)2 with carbon monoxide, carbon disulfide, and diphenylacetylene resulted in the irreversible coordination of the molecule to the metal. In the presence of pyridine, the polysiloxane-bound complex 2(Tn)2-(Di-C6-Di)2 oxidatively added hydrogen to give the octahedrally configurated complex [ClRhH2(Py)(P ∼ O)2] [6(Tn)2(Di-C6-Di)2]. Treatment of dry 2(Tn)2-(Di-C6-Di)2 with ethene led to the reversible formation of the corresponding complex. Although the materials display low surface areas, at least 75% of the rhodium centers within the matrix are accessible to the rather bulky tolan molecules. The complexes 2(Tn)2(Di-C6-Di)y (y (y = 2, 8) show high activities and selectivities in the hydrogenation of tolan. The conversion was found to depend markedly on the amount of co-condensate (D0-C6-D0) and on the polarity of the solvent. The polysiloxane-bound complexes 2(Tn)2(Di-C6-Di)y are more active than their monomeric congener 2 a(T0)2.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031116
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  • 9
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    A Study of the Gas-Phase Reactivity of Neutral Alkoxy Radicals by Mass Spectrometry: α-Cleavages and Barton-type Hydrogen MigrationsDedicated to Sir Derek H. R. Barton (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1866-1883 
    Details
    ISSN: 0947-6539
    Keywords: alkoxy radicals ; Barton reaction ; density functional calculations ; mass spectrometry ; radicals ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactivity of neutral alkoxy radicals in the absence of any interfering intermolecular interactions is investigated by means of the recently introduced method of neutral and ion decomposition difference (NIDD) spectra. These are obtained from quantitative analysis of the corresponding neutralization-reionization (NR) and charge reversal (CR) mass spectra. The following trends emerge: alkoxy radicals with short (C1—C3) or branched alkyl chains give rise to α-cleavage products, whereas longer-chained alkoxy radicals undergo 1,5-hydrogen migrations from carbon to oxygen, that is, Barton-type chemistry. This facile rearrangement has been studied in detail for n-pentoxy radicals by isotopic labeling experiments and computation at the Becke 3 LYP/6-31 G* level of theory. Further, the NIDD spectra of 3-methylpentoxy radicals permit for the first time the identification of the diastereoselectivity of the gas-phase hydrogen migrations. The results from the NIDD method are compared to those from earlier studies in the condensed phase. This new mass spectrometric approach is suggested as a tool for the examination of intramolecular reactions of free alkoxy radicals which can usefully complement theoretical studies.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031120
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  • 10
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    Asymmetric Addition Reactions with Optimized Selenium Electrophiles (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1894-1902 
    Details
    ISSN: 0947-6539
    Keywords: asymmetric synthesis ; chirality ; diselenides ; selenium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of various nonracemic diselenides by different methods is described. These diselenides are precursors for optically active selenium electrophiles. Their facial selectivity upon addition to styrene was investigated with respect to the chiral moiety neighboring the selenium. Diselenides 1 i, 1 n, and 1 v yielded addition products 7 with diastereomeric excesses up to 95%. Some diselenides, intermediates, and products of the addition reaction were investigated by 77Se NMR spectroscopy.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/chem.19970031123
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  • 11
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    2,3,7,8,12,13,17,18-Octafluoro-5,10,15,20-Tetraphenylporphyrin: First Synthesis and X-Ray Crystal Structure of the ZnII Complex (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1890-1893 
    Details
    ISSN: 0947-6539
    Keywords: heterocycles ; fluorine ; porphyrinoids ; zinc ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2,3,7,8,12,13,17,18-Octafluoro-5,10,15,20-tetraphenylporphyrin has been prepared from 3,4-difluoropyrrole and benzaldehyde under Lindsey conditions. An X-ray crystal structure study of its ZnII complex has shown that the macrocycle core is nonplanar, a result in apparent contradiction with a blue-shifted UV/Vis spectrum. The results reported here demonstrate that a wide range of β-octafluoro-meso-arylated porphyrins, a new class of highly electron-deficient ligands, are potentially accessible from 3,4-difluoropyrrole, thus opening the door to, inter alia, efficient and robust oxidation catalysts.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970031122
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  • 12
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    Cover page (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. cpi 
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    ISSN: 0947-6539
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031201
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  • 13
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    Structure and Properties of Ba6Ni25S27 (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1884-1889 
    Details
    ISSN: 0947-6539
    Keywords: conducting materials ; electronic structure ; magnetic properties ; phase transitions ; sulfur ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ba6Ni25S27, synthesized by solid-state reaction of BaS, NiS, and Ni at 675°C, is cubic (Pm3m, a = 10.057(1) Å). The structure was refined by using powder X-ray diffraction and Rietveld methods with Rp = 6.28%, Rwp = 8.13%, χ2 = 3.120. The structure, isotypic with Ba6Co25S27, consists of an extended network of Ni8S14 pseudo-cube clusters, NiS6 octahedra, and Ba6S octahedra. Extended Hückel calculations of this compound indicate the band structure near the Fermi level to be composed mostly of d-character orbitals of tetrahedral Ni, and reveal a peak in the density of states slightly below the Fermi level. The temperature dependence of the electrical resistivity exhibits a local maximum with thermal hysteresis at around 230 K. Above and below this transition, the slope of the resistivity is positive, with a room-temperature resistivity (ρ = 0.23 mωcm) in the range for that of a poor metal conductor. Magnetic susceptibility measurements from 4 to 900 K indicate a sharp change in slope at around 225 K, with a steadily increasing susceptibility up to 900 K. The susceptibility below 225 K suggests Pauli paramagnetic behavior. Low-temperature powder X-ray diffraction and subsequent structure refinement shows that the lattice parameter, a, undergoes a slight change in slope at temperatures of around 235 K.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970031121
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  • 14
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    Masthead (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997) 
    Details
    ISSN: 0947-6539
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031202
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  • 15
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    Graphical abstract (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1911-1916 
    Details
    ISSN: 0947-6539
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031203
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  • 16
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    Metallic Hydrogen at High Pressures and Temperatures in JupiterFrom a lecture delivered at the meeting of the British Association for the Advancement of Science at the University of Birmingham, September 9-13, 1996. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1921-1924 
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    ISSN: 0947-6539
    Keywords: high-pressure chemistry ; high-temperature chemistry ; hydrogen ; Jupiter ; metallic hydrogen ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electrical conductivities of hydrogen were measured recently at 93-180 GPa (0.93-1.8 Mbar), 0.28-0.36 mol cm-3, and 2000-4000 K. Shock temperatures were measured up to values of 5200 K at 0.83 Mbar. The conductivities indicate a continuous transition from a semiconducting to metallic fluid at 140 GPa and 3000 K. The results indicate that hydrogen becomes metallic much closer to the surface of Jupiter than thought previously and that Jupiter has no core-mantle boundary.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970031205
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  • 17
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    Drug Discovery by Combinatorial Chemistry - the Development of a Novel Method for the Rapid Synthesis of Single CompoundsFrom a lecture delivered at the meeting of the British Association for the Advancement of Science at the University of Birmingham, September 9-13, 1996. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1917-1920 
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    ISSN: 0947-6539
    Keywords: combinatorial chemistry ; compound libraries ; drug research ; solid-phase synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Through the advantages conferred in the speed of synthesis, combinatorial chemistry is making a significant impact on the process of drug discovery. The mix-and-split paradigm has been an effective method for the production of compound mixtures, although there is now a need for new, fast library approaches to generate well-characterised single compounds. Having already demonstrated the successful preparation and application of library mixtures, we have now developed a novel combinatorial method for the production of single compounds.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970031204
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  • 18
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    Molecules in SpaceFrom a lecture delivered at the meeting of the British Association for the Advancement of Science at the University of Birmingham, September 9-13, 1996. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1929-1932 
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    ISSN: 0947-6539
    Keywords: gas-phase chemistry ; interstellar chemistry ; ion-molecule reactions ; star formation ; surface chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The distribution and nature of interstellar matter in the Galaxy is described. The chemical processes by which the rich variety of molecular species arise are briefly sketched. The importance of interstellar molecules in influencing the evolution of the Galaxy is emphasized.
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    Gas-Phase Reactions at Low Temperatures: Towards Absolute ZeroFrom a lecture delivered by I. W. M. S. at the meeting of the British Association for the Advancement of Science at the University of Birmingham, September 9-13, 1996. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1925-1928 
    Details
    ISSN: 0947-6539
    Keywords: gas-phase chemistry ; interstellar chemistry ; kinetics ; low-temperature chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Very recently, methods have been developed for studying the rates of chemical reactions between electrically neutral species in the gas phase at temperatures as low as 13 K. Here we review this exciting development in gasphase chemical kinetics. Emphasis is placed on the importance of the information which the experiments have provided, both from the viewpoint of posing new questions about the factors which control chemical reactivity and because of their relevance to the modelling of molecular synthesis in interstellar clouds.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970031206
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    Opposite Stereochemical Effects Exerted by CeCl3 and TiCl4 on the Lewis Acid Mediated Reduction of α-Alkyl-β-ketophosphine Oxides with Metallic Hydrides: A Highly Stereoselective Protocol for the Synthesis of syn and anti α-alkyl-β-Hydroxyphosphine Oxides (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1941-1950 
    Details
    ISSN: 0947-6539
    Keywords: alkenes ; asymmetric synthesis ; natural products ; Lewis acids ; phosphane oxides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A general, highly efficient methodology for obtaining both syn and anti β-hydroxyphosphine oxides by reduction of the corresponding β-ketophosphine oxides is described. The nature of the Lewis acid was found to be pivotal in determining the outcome of these reactions. Strongly chelating TiCl4 led to the anti isomer in high diastereoisomeric excess in noncoordinating solvents (CH2Cl2) at -78°C with BH3/py as reducing agent, while nonchelating CeCl3 gave a high excess of the syn isomer in coordinating solvents (THF) at the same temperature with LiBH4 as reducing agent. In the latter case, CeCl3 is essential in achieving high yields and stereoselectivity, since it allows the reaction to be performed at low temperatures. Otherwise, higher temperatures (0°C) are required, which lower both yields and selectivities. Moreover, each step of the protocol for the synthesis of stereodefined disubstituted olefins from alkylphosphine oxides (Warren's modification of the Horner procedure) has been optimized, and the optimized procedure has been applied to the synthesis of muscalure, the pheromone of the domestic fly.
    Additional Material: 4 Tab.
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    Total Synthesis of Oxazole- and Cyclopropane-Containing Epothilone A Analogues by the Olefin Metathesis Approach (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1957-1970 
    Details
    ISSN: 0947-6539
    Keywords: epothilone ; oxazoles ; cyclopropanes ; metathesis ; total synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For structure-activity relationship studies, two series of epothilone A (1) analogues have been designed and synthesized, one containing an oxazole moiety instead of the thiazole heterocycle and the other containing a spirocyclopropane moiety in place of the gem-dimethyl group at position C-4 (4,4-ethano-epothilones). The olefin metathesis strategy in solution was utilized for the chemical synthesis of these compounds starting with key building blocks 7-9 for the oxazole series (compounds 2, 14-18, 21-26) and building blocks 8, 30, and 31 for the 4,4-ethano series (compounds 3,39-43, 46-51). The convergent strategy towards the designed epothilone A series involved a) an aldol condensation reaction, b) an esterification reaction, c) an olefin metathesis reaction catalyzed by [RuCl2(=CHPh)-(PCy3)2], and d) epoxidation of the macrocycle double bond.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970031211
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    Controlling Self-AssemblyFrom a lecture delivered by J. F. S. at the meeting of the British Association for the Advancement of Science at the University of Birmingham, September 9-13, 1996. This paper is Part 26 in the series “Molecular Meccano” for Part 25, see S. Menzer, A. J. P. White, D. J. Williams, M. Belohradsky, C. Hamers, F. M. Raymo, A. N. Shipway, J. F. Stoddart, Macromolecules, in press. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1933-1940 
    Details
    ISSN: 0947-6539
    Keywords: catenanes ; molecular recognition ; pseudorotaxanes ; supramolecular chemistry ; translational isomerism ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As a result of cooperative noncovalent bonding interactions (namely, π-π stacking, [CH…O] hydrogen bonding, and [CH…π] interactions) supramolecular complexes and mechanically interlocked molecular compounds - in particular pseudorotaxanes (precatenanes) and catenanes - self-assemble spontaneously from appropriate complementary components under thermodynamic and kinetic control, respectively. The stereoelectronic information imprinted in the components is crucial in controlling the extent of the formation of the complexes and compounds in the first place; moreover, it has a very significant influence on the relative orientations and motions of the components. In other words, the noncovalent bonding interactions - that is, the driving forces responsible for the self-assembly processes - live on inside the final superstructures and structures, governing both their thermodynamic and kinetic behavior in solution. In an unsymmetrical [2]catenane, for example, changing the constitutions of the aromatic rings or altering the nature of substituents attached to them can drive an equilibrium associated with translational isomerism in the direction of one of two or more possible isomers both in solution and in the solid state. Generally speaking, the slower the components in mechanically interlocked compounds like catenanes and rotaxanes move with respect to each other, the easier it is for them to self-assemble.
    Additional Material: 9 Ill.
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    Gold Clusters and Colloids in Alumina NanotubesDedicated to Professor Achim Müller on the occasion of his 60th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1951-1956 
    Details
    ISSN: 0947-6539
    Keywords: clusters ; colloids ; gold ; nanostructures ; quantum wires ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fabrication of a supported and insulated quantum wire would be of great interest, especially if electronic information could be accessed to determine charging and conductivity profiles. The feasibility of forming one-dimensional configurations of ≈ 15 nm gold colloids and 1.4 nm gold clusters via template methods of synthesis has now been demonstrated. The template host material consisted of porous alumina membranes formed by an electrochemical anodic process. The pores of the membrane, and hence the parallel pore channels, were packed in a hexagonal array. Alumina membranes are excellent template materials because of their high degree of order, thermal and chemical stability, and optical clarity. Pore diameter was controlled by regulation of the applied anodic potential (ca. 1.4 nm V-1). The pore channels were filled by one of three methods: vacuum induction (colloids only), electrophoresis (clusters only), or immersion (clusters, which were then converted into colloids by heating). Rudimentary wires consisting of colloids and clusters were successfully formed. In both cases, the diameter of the pore channel exceeded that of the clusters or colloids. The wires thus formed conformed to the pore channel by forming helical secondary structures. It was not possible to form contiguous wires of clusters by immersion, or of colloids formed from clusters after heating. Composites (consisting of the gold-alumina system) were a bright scarlet color with an absorption maximum (λmax) at 519.5 nm. This is an unexpected result for spherical and small-diameter (10 nm) gold colloids, which normally absorb at λmax 525-530 nm, a ruby-red color. Possible causes of this small but remarkable blue shift are discussed below. A new Au55 cluster ligand system consisting of a silsesquioxane-derivatized thiol is also described.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970031210
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    Total Synthesis of Oxazole- and Cyclopropane-Containing Epothilone B Analogues by the Macrolactonization Approach (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1971-1986 
    Details
    ISSN: 0947-6539
    Keywords: epothilone ; oxazoles ; cyclopropanes ; total synthesis ; macrolactonizations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to probe structure-activity relationships in the epothilone area, two series of epothilone B analogues have been designed and synthesized. The first series containing an oxazole moiety in place of a thiazole on the side chain was constructed by utilizing key intermediates 7-9 or 10, 12, and 13 (Scheme 1), whereas the second series containing an ethano group instead of the gem-dimethyl group at position 4 was synthesized from fragments 42 and 43. A Yamaguchi-type macrolactonization reaction was used to construct the macrocycle from a secoacid, which was assembled, in both cases, by means of a) an aldol reaction, b) an Enders alkylation, and c) a Wittig-type reaction. This convergent strategy provided access to oxazole analogues 2,4,29-32 and 4,4-ethano derivatives 3,40,60-63 for biological studies.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970031212
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    Polymeric [(Me3Sn)3Rh(SCN)6]: A Novel “Super-Prussian-Blue” Derivative Containing the Nonlinear -SCN-Sn-NCS- SpacerDedicated to Professor Gottfried Huttner on the occasion of his 60th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1987-1991 
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    ISSN: 0947-6539
    Keywords: coordination polymers ; Prussian blue ; rhodium ; structure elucidation ; tin ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The new coordination polymer [(Me3SnIV)3RhIII(SCN)6] = 3∞[Rh{μ-(SCNSnMe3NCS)}3] (5) is readily accessible by straightforward self-assembly of [Rh(SCN)6]3- and (dehydrated) {Me3Sn}+aq ions. The architecture of 5 is strongly reminiscent of “super-Prussian-blue” systems reported earlier: there is a three-dimensional (3-D) framework involving {Rh8} pseudocubes as the basic building blocks, the Rh3+ ions being held apart by novel, nonlinear {SCN-SnMe3-NCS} spacers (d(Rh…Rh) = 1.27 nm). The complete lattice consists of two equivalent and independent, ideally interwoven 3-D frameworks. Three homologues of 5 with slightly modified R3Sn units (R = Et, nPr and nBu) have been prepared as well, but display X-ray powder diffraction patterns notably different from that of 5.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970031213
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    Electrochemically Induced Molecular Motions in Pseudorotaxanes: A Case of Dual-Mode (Oxidative and Reductive) Dethreading (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1992-1996 
    Details
    ISSN: 0947-6539
    Keywords: cyclic voltammetry ; logic gates ; molecular devices ; pseudorotaxanes ; spectroelectrochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrochemical and spectroscopic properties of a pseudorotaxane formed in acetonitrile solution by self-assembly of a wire-type electron donor based on the tetrathiafulvalene unit and the cyclobis(paraquat-p-phenylene) tetracationic electron acceptor have been investigated. We show that a) reversible dethreading/rethreading cycles of the pseudorotaxane can be performed by either oxidation and successive reduction of the electron-donor wire or reduction and successive oxidation of the electron-accepting tetracationic cyclophane, and b) because of this special behavior, the input (electrochemical)/output (absorption spectrum) characteristics of this molecular-level system correspond to those of an XNOR logic gate.
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    URL: http://dx.doi.org/10.1002/chem.19970031214
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    Oligonucleotide Analogues with 4-Hydroxy-N-Acetylprolinol as Sugar Substitute (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1997-2010 
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    ISSN: 0947-6539
    Keywords: antisense agents ; chiral recognition ; oligonucleotides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Modified oligonucleotides incorporating trans-4-hydroxy-N-acetyl-L-prolinol (trans-4-HO-L-NAP) or its D-analogue as sugar substitute were synthesised with adenine and thymine as nucleobases. All-adenine oligonucleotides built from (2S,4S) or (2R,4R)-cis-4-hydroxy-N-acetylprolinol were likewise prepared. Hybridisation studies revealed that heterocomplexes formed between polyU and homochiral trans-4-hydroxy-N-acetylprolinol-based oligomers of the same as well as of opposite chirality (polyU/trans-DA*13 and polyU/trans-LA*13). The former, however, were triple-stranded. Other complexes with ribonucleic acids were polyA/trans-LT*13 and polyU/cis-LA*13. Heteroduplexes with deoxynucleic acids were formed between trans-LA*13 and oligothymidylate. Interaction was also observed for cis-LA*13 and oligothymidylate, but not with the D-hydroxyprolinol analogues. Microcalorimetry proved this interaction to be the formation of a triple-stranded complex. Two heteroduplexes, trans-LA*13/dT13 and trans-LA*13/polyU, had similar or slightly increased stability when compared to the natural dA13/dT13 or dA13/polyU systems. Microcalorimetry clearly indicated the formation of a duplex, in contrast to interactions with N-acetylprolinol oligonucleotides of different stereochemistry. Moreover, the enthalpy change was of the same magnitude but the association constant was slightly lower. Natural nucleic acids thus clearly prefer hybridisation with L-hydroxyprolinol oligomers over D-hydroxyprolinol oligomers. For the series investigated, the L-trans oligomers (Figure 1) seem best to mimic natural oligonucleotides. These modified oligonucleotides formed homocomplexes if both strands were of the same chirality, that is, homocomplexes formed between trans-LA* and trans-LT* and between trans-DA* and trans-DT*, reflecting the isochiral pu-py pairing found in natural nucleic acids. Once more, however, calorimetry proved these to be triplex interactions. Heterochiral pairing was not observed between modified oligonucleotides, but only between modified oligonucleotides and natural polyU. The thermal stabilities of these heterochiral complexes differed clearly.
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    Rapid Coupling of Methyl Iodide with Aryltributylstannanes Mediated by Palladium(0) Complexes: A General Protocol for the Synthesis of 11CH3-Labeled PET Tracers (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 2039-2042 
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    ISSN: 0947-6539
    Keywords: arylphosphanes ; C-C coupling ; isotopic labeling ; palladium ; tin ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of methyl iodide and (excess) aryltributylstannane to give a methylarene has been studied with the focus on the realization of rapid coupling for incorporation of short-lived radionuclides into bioactive organic compounds. The coupling of methyl iodide with tributylphenylstannane (40 equiv) is accomplished in 〉90% yield within 5 min at 60°C with a tri-o-tolylphosphine-bound, coordinatively unsaturated Pd0 complex together with a CuI salt and K2CO3 in DMF. This protocol is applicable to a variety of homo- and heteroaromatic tin compounds, to give the corresponding methylated derivatives. The effects of the tri-o-tolylphosphine ligand, a Cu(I) salt, and DMF are discussed. This new protocol provides a firm chemical basis for the synthesis of 11CH3-incorporated PET tracers.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/chem.19970031219
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    Some Remarks on the Occurrence and Properties of Knödel (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 2081-2081 
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    ISSN: 0947-6539
    Keywords: carbohydrates ; correspondence ; dendrimers ; micelles ; nanospheres ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031225
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    Mechanisms and Stereochemistry of Acid-Induced Ring Opening of Optically Active 1,2-Propene Oxides in the Gas PhaseChiral ions in the gas phase, part 3. Parts 1 and 2: ref. [1]. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 2063-2070 
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    ISSN: 0947-6539
    Keywords: chirality ; gas-phase chemistry ; ion-molecule reactions ; regioselectivity ; ring-opening reactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The acid-induced ring opening of (S)-( - )-1,2-propene oxide (1S) and (R)-(+)-1,2-propene oxide (1R) has been investigated in gaseous CH4 and CH3F at 720 torr and in the presence of a nucleophile, NuOH (Nu = H or CH3). The mechanism of the ring-opening reaction has been assessed by modulating the composition of the gaseous mixture. Two reaction pathways are operative in the gas phase, both proceeding through complete inversion of configuration of the reaction center. A first process is detectable only in the CH3F/H2O systems and takes place within a persistent proton-bound complex generated by interaction of the epoxide with the CH3OH+2 ion, formed by methylation of H2O with (CH3)2F+. Such an intracomplex ring-opening pathway proceeds through proton transfer from the CH3OH+2 ion to the epoxide followed by motion of the neutral CH3OH moiety around the 1-H-oxonia-2-methyl-cyclo-propane structure (H-1R or H-1S) (k〈108 s-1) before attacking the ring carbons from the rear. In all the other systems with added CH3OH, this intracomplex pathway is preceded by a faster “extracomplex” pathway involving the attack of an external CH3OH molecule on the proton-bound adduct. The regioselectivity of the intracomplex process is similar to that of the extracomplex pathway. Both are characterized by a slight preference for the Cβ center of H-1 R (or H-1S) (extra-complex path regioselectivity: α/β = 0.72±0.05; intracomplex path regioselectivity: α/β = 0.71±0.05). The regioselectivity of H-1 R (or H-1S) is substantially different from that of the 1-Me-oxonia-2-methyl-cyclopropanes (Me-1 R or Me-1 S) toward the same nucleophile NuOH (α/β = 4.1±0.35 (Nu = H); 2.28±0.16 (Nu = CH3)). This difference is attributed to a transition structure wherein the Cα-O bond rupture increases from H-1 R (or H-1 S) to Me-1 R (or Me-1 S) and in passing from CH3OH to H2O. The regioand stereoselectivity of the gas-phase acid-induced ring opening of 1 S and 1 R are compared with those of related reactions carried out in solution.
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    Reaction of „Jordan′s Cation“ [Cp2ZrCH3(thf)]+ with Amino Acid-Derived Isocyanates - A First Synthetic Route to Oligopeptide-Modified Group 4 Bent Metallocene Cation SystemsDedicated to Professor Waldemar Adam on the occasion of his 65th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1521-1525 
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    ISSN: 0947-6539
    Keywords: isocyanates ; „Jordan′s cation“ ; metallocenes ; peptides ; zirconium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The organometallic cation [Cp2ZrCH3(thf)]+, employed as the tetraphenylborate salt (1), reacts cleanly in 1:1 stoichiometry with the isocyanates 2 derived from valine methyl ester or valylvaline methyl ester, respectively. In each case addition of the Zr-CH3 group to the isocyanate sp-carbon center is observed with formation of a functionalized zirconocene cation derivative containing a chelating N-metallated N-acetylvaline methyl ester (3a) or N-acetylvalylvaline methyl ester (3b) moiety, respectively, coordinated in the bent metallocene s̰-ligand plane. The spectroscopic data of 3, supported by an X-ray crystal structure analysis of the zirconated dipeptide derivative 3b, have revealed the presence of chelating (η1-O:η1-N)-coordination of the terminal N-acetyl groups in addition to a Zr-O=C interaction with the adjacent valyl amido group.
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    Cover page (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. cpi 
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    ISSN: 0947-6539
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 8 Ill.
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    Masthead (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997) 
    Details
    ISSN: 0947-6539
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031002
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    Formal [4 + 3], [4 + 2], [4 + 1] cycloadditions and acid-base reaction of 2-methyl-1,3-dimorpholino-1,3-butadiene with Fischer carbene complexes (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1629-1637 
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    ISSN: 0947-6539
    Keywords: C-H activation ; carbene complexes ; cycloadditions ; 1,3-diamino-1,3-butadiene ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Methyl-1,3-dimorpholino-1,3-butadiene 1 reacted with α,β-unsaturated Fischer carbene complexes to give a wide range of different products depending on the substitution pattern. Thus, sevenmembered rings (4, 5 and 6) could be obtained from chromium complexes 2 with aromatic or vinylic groups at the β position. Similar results were observed when α-methyl-substituted carbene complex 7 a was used. Six-membered carbocycles (derivatives of cycloadducts 12 and 13) were isolated after reaction with both chromium and tungsten complexes bearing one or two alkyl groups at the β position (10 and 11). Moreover, cyclopentenones 20 were the main products when the starting carbene complexes were alkyl-substituted at both α and β positions (19a, b) or when aromatic (19c, d) instead of vinylic complexes were used. A bicyclo[4.1.0]heptene system 18 has also been obtained in the special case of reaction with β,β-dimethylvinylchromium complex 13b; its formation could be explained as a formal carbene insertion into a C-H bond. The behaviour of diene 1 towards alkoxymethylcarbene complexes 22 was unusual. The different reaction products (cyclopentadienes 23, bicyclo[3.1.0]hexenes 24, aromatic amine 25 and metallatrienes 26) imply a mechanism in which the deprotonation of the carbene complex by the diene is followed by Michael addition to the iminium salt formed.
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    In Search for Mononuclear Helical Lanthanide Building Blocks with Predetermined Properties: Triple-stranded Helical Complexes with N,N,N',N'-tetraethylpyridine-2,6-dicarboxamide (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1646-1659 
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    ISSN: 0947-6539
    Keywords: carboxamides ; helical structures ; lanthanides ; luminescence ; tridentate ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ligand N,N,N',N'-tetra-ethylpyridine-2,6-dicarboxamide (L9) reacts with trivalent lanthanide ions (LnIII) to give stable mononuclear triple-stranded helical complexes [Ln(L9)3]3+ (Ln = La to Lu). The crystal and molecular structures of [La(L9)3](ClO4)3.2.5C2H5CN (8) and [Eu(L9)3](TfO)3.2THF (9) show that the three ligand strands are each meridionally tricoordinated to produce a pseudo-tricapped trigonal prismatic arrangement of the nine donor atoms (six amide O and three pyridine N) around LnIII. The distortions in the LaIII coordination sphere of 8 are more significant than for EuIII in 9, and the photophysical studies on Eu-doped (2%) La, Gd, and Lu complexes confirm a better structural match of L9 for the heavy LnIII ions. The separation of contact and pseudo-contact contributions to the induced lanthanide paramagnetic NMR shifts in [Ln(L9)3]3+ shows that the triple-helical structure is maintained in acetonitrile, but a minor structural change relative to that observed in the solid state occurs between TbIII and ErIII leading to two distinct isostructural series for Ln = La-Tb and Ln = Er-Lu. The origin of this effect together with its consequences for the dynamic helical (P→M) interconversion and stability of [Ln(L9)3]3+ in solution are discussed. A detailed investigation of the emission properties of [Ln(L9)3]3+ (Ln = Eu, Tb) shows that mixed pyridine-carboxamide ligands can be used to simultaneously optimize the structural and photophysical properties in mononuclear triple-helical lanthanide building blocks.
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    Type B Semiconductor Photocatalysis: The Synthesis of Homoallyl Amines by Cadmium Sulfide-Catalyzed Linear Photoaddition of Olefins and Enol/allyl Ethers to N-Phenylbenzophenone ImineHeterogeneous Photocatalysis, part XVI. Part XV: W. Schindler, H. Kisch, J. Photochem. Photobiol. A: Chem., 1997, 103, 257. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1638-1645 
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    ISSN: 0947-6539
    Keywords: cadmium sulfide ; catalysis ; photochemistry ; semiconductors ; unsaturated amines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Homoallyl amines were synthesized by visible-light irradiation of CdS powder in the presence of N-phenylbenzophenone imine and cyclohexene, 2,3-dihydrofuran, 2,5-dihydrofuran, 3,4-dihydropyran, 2-pentene, cyclopentene, 1-methylcyclohexene, or α-pinene. The structures of the products from the last three olefins were determined by single-crystal X-ray analysis to prove that C-alkylation of the imine had occurred. Thus, the reaction is formally an insertion of the imine into an allylic C-H bond of the olefin. It is proposed that a photogenerated electron-hole pair reduces the imine to an α-aminodiphenylmethyl radical and oxidizes the olefin with concomitant deprotonation to the corresponding allyl radical. Heterocoupling of these intermediates affords the final addition product. The overall reaction is therefore classified as type B semiconductor photocatalysis. The presence of acetic acid accelerates the reaction by rendering the reduction potential of the imine more positive. In the series 2,5-dihydrofuran/cyclopentene/3,4-dihydropyran, the decrease in apparent quantum yield with increasing driving force of olefin oxidation points to a significant contribution of secondary back electron transfer.
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    A Highly Convergent Total Synthetic Route to Glycopeptides Carrying a High-Mannose Core Pentasaccharide Domain N-linked to a Natural Peptide Motif (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1617-1628 
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    ISSN: 0947-6539
    Keywords: glycals ; glycopeptides ; glycosylations ; β-mannosides ; oligosaccharides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-Linked glycopeptides were synthesized by condensation of a highmannose anomeric amine bearing a pentasaccharide with aspartic-acid-containing tri- and pentapeptides through the agency of IIDQ. The pentasaccharide portion, corresponding to the „core“ region of all asparagine-linked glycoproteins, was assembled by means of glycal-derived thioethyl donors and glycal acceptors. The central mannose residue was established by inversion of the C2 hydroxyl of a glucosyl precursor in the pentasaccharide. The protecting-group scheme employed allows the extension of the pentasaccharide through the terminal mannose units. While a fully convergent coupling of the high-mannose carbohydrate to the peptide domain has thus been accomplished for the first time with a fully synthetic sugar, the stereochemical integrity of the anomeric center of the carbohydrate domain was not maintained and a mixture of glycopeptides was obtained.
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    A Square As4 and a Prismatic As6 Structure as Complex Ligands (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1494-1498 
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    ISSN: 0947-6539
    Keywords: arsenic ; cobalt ; density functional calculations ; structural elucidation ; Zintl anions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [As7(SiMe3)3] reacts with [(Cp*CoCl)2] to give black crystals of the ionic compound [(Cp*Co)3As6][CoCl4] (1). The cation [(Cp*Co)3As6]2+ consists of an As6 prism, with squares capped by [Cp*Co] fragments. When [(CptBuCoCl)2] is used instead of [(Cp*CoCl)2] in the reaction, dark red crystals of [(CptBuCo)3As6][CoCl3(thf)]2 (2) and green-black crystals of [(CptBuCo)2As4][Co3Cl8(thf)2] (3) can be obtained. The cation in 2 shows a structure very similar to that of 1. The [(CptBuCo)2As4]2+ cations in 3 can be described as a triple-decker sandwich complex with two [CptBuCo]+ fragments bridged by an As4 ligand. Density functional calculations reproduce the experimental data of 1 and 3 and allow an interpretation of molecular electronic structure and bonding in these and related compounds with As replaced by P and Co by Fe.
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    1′,5′-Anhydrohexitol Oligonucleotides: Hybridisation and Strand Displacement with Oligoribonucleotides, Interaction with RNase H and HIV Reverse Transcriptase (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1513-1520 
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    ISSN: 0947-6539
    Keywords: duplex ; gel mobility ; nucleic acids ; oligonucleotides ; strand displacement ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hexitol nucleic acids (HNAs) with four natural bases form stable and sequence-selective duplexes with RNA. This was investigated by Tm determinations and gel shift experiments. The CD spectra of an HNA-RNA duplex show similarities with the CD spectra of the A-form of dsRNA. Single-stranded HNAs are able to induce strand displacement in a double-stranded RNA sequence. An HNA-RNA duplex is a poor substrate for RNase H, and can inhibit the RNase H-mediated cleavage of a natural DNA-RNA substrate. The HNA-RNA hybrid enhances the activity of HIV reverse transcriptase.
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    Relaxometric Determination of the Exchange Rate of the Coordinated Water Protons in a Neutral GdIII Chelate (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1499-1504 
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    ISSN: 0947-6539
    Keywords: gadolinium ; NMR spectroscopy ; prototropic exchange ; rare earth compounds ; water exchange rate ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The exchange rate of the coordinated water molecule in the neutral complex [Gd(DTPA-BBA)(H2O)] (DTPA-BBA = 1,7-bis[(N-benzylcarbamoyl)methyl]-1,4,7-triazaheptane-1,4,7-triacetate or diethylenetriaminopentaacetate N,N′-bis(benzylamide)) is slower than in the parent complex [Gd(DTPA)(H2O)]2-. From the analysis of the temperature dependence of the solvent 17O NMR transverse relaxation time in an aqueous solution of the paramagnetic complex, a value of 4.5 × 105 s-1 (at 298 K) is obtained for the exchange rate of the coordinated water molecule. This rate constant does not vary in the pH range 7-12. Conversely, over the same pH range and at 298 K and 20 MHz, the longitudinal water proton relaxivity increases from 4.8 to 6.5 s-1 mM-1. The analysis of the dependence of the longitudinal water proton relaxation rate on magnetic field and temperature at pH 7 and pH 12 shows that the increase in relaxivity at basic pH has to be assigned to the contribution of the prototropic exchange at the water molecule in the inner coordination sphere of the metal ion. This exchange process is catalyzed by OH- ions (kP = 1.7 × 109 M-1 s-1 at 298 K) and causes an increase in the observed relaxivity when it occurs at a rate larger than the exchange rate of the entire water molecule. At pH 12 the limiting effect of the slow exchange rate for the coordinated water molecule is removed, and the longitudinal water proton relaxivity measured at this pH then represents the maximum value attainable for this complex.
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    Poly(triacetylene) Oligomers: Synthesis, Characterization, and Estimation of the Effective Conjugation Length by Electrochemical, UV/Vis, and Nonlinear Optical MethodsDedicated to Professor Dieter Seebach on the occasion of his 60th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1505-1512 
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    ISSN: 0947-6539
    Keywords: conjugation length ; electrochemistry ; nonlinear optics ; oligomers ; poly-(triacetylene)s ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(triacetylene)s [PTAs, —(C≡C—CR=CR—C≡C)n-] are a new class of linearly conjugated polymers with a nonaromatic all-carbon backbone. To explore structure-property relationships in PTAs, we prepared a series of monodisperse oligomers ranging from monomer to hexamer by oxidative Glaser-Hay coupling of a bifunctional („chain-forming“) (E)-hex-3-ene-1,5-diyne in the presence of an endcapping unit. All six oligomers are amazingly stable towards exposure to light, air, and temperatures beyond their melting points. They have been fully characterized and are readily soluble in a wide range of solvents. The conjugated rods are reversibly reduced in one-electron transfer steps and cannot be oxidized below +1.23 V vs. Fc/Fc+. The effective conjugation length in PTAs was estimated from the electronic absorption (UV/Vis) data, and various evaluation methods yielded convergence of the optical properties in the range of 7 to 10 monomer units. The nonresonant second-order molecular hyperpolarizability γ was measured in CHCl3 by means of the third harmonic generation (THG) at Δ = 1.907 μm. A plot of γ/n vs. n revealed a power law γ ≈ na for γ with a fitted exponent a = 2.5 ∓ 0.1. From the THG measurements, an effective conjugation length of about 10 monomer units was found, in surprisingly good agreement with the value obtained from UV/Vis spectroscopy data.
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    Graphical abstract (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1552-1556 
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    ISSN: 0947-6539
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970031003
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    The Ineluctable Need for in Situ Methods of Characterising Solid Catalysts as a Prerequisite to Engineering Active Sites (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1557-1562 
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    ISSN: 0947-6539
    Keywords: enzyme catalysis ; EXAFS spectroscopy ; heterogeneous catalysis ; synchrotron radiation ; X-ray absorption spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ultimate success in the design of solid oxide catalysts as well as other covalently bonded or heterogenised organometallic catalysts predicates knowledge of precisely what structure it is that has to be targetted. This, in turn, demands the greatest possible precision in determining, under operating conditions, the structure of the catalyst in general and of the active site in particular. Combined X-ray absorption spectroscopy and X-ray diffraction are ideal tools for such in situ investigations. Examples of such studies and of engineered catalysts, the structure of which have been determined in atomic detail, are given.
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    Strong Binding of Alkylguanidinium Ions by Molecular Tweezers: An Artificial Selective Arginine Receptor Molecule with a Biomimetic Recognition Pattern (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1537-1541 
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    ISSN: 0947-6539
    Keywords: arginine ; guanidines ; molecular recognition ; receptors ; supramolecular chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bisphosphonates 2 and 3 represent the first artificial receptor molecules for alkylguanidinium ions. They bind to the guanidinium moiety by forming a 1:1 chelate complex, stabilized by a planar network of electrostatic interactions and hydrogen bonds. This hydrogen bonding configuration is identical to the „arginine fork“ postulated by Frankel as a key element in RNA-protein recognition of the AIDS virus. Our guanidinium-bisphosphonate complexes thus constitute the first synthetic model for this important biological interaction and demonstrate that the high binding energy can be a driving force for a conformational change in the receptor (induced fit, e.g., in the RNA). Although binding of monosubstituted alkylguanidines is generally strong (Ka ≈ 10 000 in DMSO), molecular tweezer 3 recognizes N- and C-amide-protected arginine derivatives especially well (Ka ≈ 300 000 in DMSO), because an additional hydrogen bond is formed between the amide and the phosphonate. Since 3 does not bind amines effectively, it is highly selective for arginine, even in the presence of lysine or other amino acids. For di-, tri-, and tetrasubstituted guanidines the association constant remains low (Ka≤1000 in DMSO) reflecting the increase in the steric bulk of the guest.
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    Chirality in Dendritic ArchitecturesThis concepts article is a personal reflection on the many issues raised by the combination of chirality and dendrimers. The concepts presented here are partly based on several recent reports in the published literature and partly on the highly appreciated discussions with colleagues on as yet undisclosed results. In particular Bert Meijer would like to express his gratitude to Professor Hans Wynberg who stimulated him to explore all aspects of stereochemistry.Dedicated to Professor Hans Wynberg on the occasion of his 75th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1563-1570 
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    ISSN: 0947-6539
    Keywords: catalysis ; chirality ; dendrimers ; molecular recognition ; surfaces ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: At first glance the topic of chiral dendrimers seems to be a contradiction in terms. However, recent studies reveal that both the building blocks of the dendrimer and the overall dendritic architecture can be chiral and that chirality can be introduced at various levels. The expression of optical activity in these enantiomerically pure dendrimers as a result of conformational (dis)order has proven to be of special interest. In this Concepts article we present the different approaches to introducing chirality in dendritic architectures, organized through their possible impact in fields such as biocompatibility, catalysis, molecular recognition, and surface chemistry. Also, the relation between molecular chirality of core or building block and the macroscopic chirality of dendritic objects is discussed.
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    Development of Tools for the Design of Selectin AntagonistsDedicated to Professor Hans Paulsen on the occasion of his 75th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1571-1578 
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    ISSN: 0947-6539
    Keywords: carbohydrates ; molecular modeling ; preorganization ; sialyl Lewisx ; selectins ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A molecular modeling tool for the rational design of E-selectin antagonists based on the lead structure sialyl Lewisx has been developed. The binding affinity to the receptor is considerably influenced by the entropy and consequently by the antagonist's ability to place its pharmacophores in an optimal spatial arrangement, i.e., by its preorganization for binding. The computational model assesses the preorganization of a potential selectin antagonist with the aid of Monte Carlo (jumping between wells)/stochastic dynamics [MC(JBW)/SD] simulations. The model has been validated by correlating preorganization and bioactivity of several selectin antagonists. The results suggest that only preorganized compounds are likely to bind to E-selectin.
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    Complex Formation of the Antiviral 9-[2-(Phosphonomethoxy)Ethyl]Adenine (PMEA) and of Its N 1, N 3, and N 7 Deaza Derivatives with Copper(II) in Aqueous SolutionAbbreviations and definitions: 2′-AMP2-, adenosine 2′-monophosphate; 3′-AMP2-, adenosine 3′-monophosphate; ATP4-, adenosine 5′-triphosphate; M2+, divalent metal ion; PA2- = PME2-, PMEA2-, and its twofold negatively charged deaza derivatives; R-PO2-3, simple phosphate monoester or phosphonate ligand with R representing a noncoordinating residue (see also Figure 1); TuMP2-, tubercidin 5′-monophosphate (=7-deaza-5′-AMP2-). Although the IUPAC nomenclature for the deazaadenine compounds is 3H-imidazo[4,5b]pyridine-7-amine (1-deazaadenine), imidazo[4,5c]pyridine-4-amine (3-deazaadenine), and pyrrolo[2,3d]pyrimidine-4-amine (7-deazaadenine), the trivial names and the numbering system for purines are retained in the present study to facilitate the comparison with the parent compound, PMEA2-, and other adenine derivatives. For example, 1-deaza-PMEA is thus named 9-[2-(phosphonomethoxy)ethyl]-1-deazaadenine. In mathematical expressions and tables, 1-, 3-, and 7-deaza-PMEA are written as 1d-, 3d-, and 7d-PMEA. In the text the expression „PMEAs“ encompasses PMEA as well as its three deaza derivatives. Species written without a charge either do not carry one or represent the species in general (i.e., independent of their protonation degree); which of the two possibilities applies is always clear from the context. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1526-1536 
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    ISSN: 0947-6539
    Keywords: adenine ; isomerizations ; NMR spectroscopy ; nucleotides ; stability constants ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stability constants of the 1:1 complexes formed between Cu2+ and the anions of the N 1, N 3, and N 7 deaza derivatives of 9-[2-(phosphonomethoxy)-ethyl]adenine (PA2-), Cu(H;PA)+ and Cu(PA), were determined by potentiometric pH titration in aqueous solution (25 °C; I = 0.1 M, NaNO3) and compared with previous results for 9-[2-(phosphonomethoxy)ethyl]adenine (PMEA2-) and (phosphonomethoxy)ethane (PME2-). A microconstant scheme reveals that in Cu(H;PA)+ Cu2+ is coordinated to the nucleobase, H+ being at the phosphonate group, in about 90% of the Cu(H;PMEA)+ and Cu(H;1-deaza-PMEA)+ species, but only in about 37% and 12% of the corresponding complexes with H(3-deaza-PMEA)- and H(7-deaza-PMEA)-, respectively. Straight-line plots of log KCuCu(R-PO3) versus pKHH(R-PO3) for simple phosph(on)ate ligands show that all the Cu(PA) complexes, including those with PMEA2- and PME2-, are more stable than expected simply from the basicity of the -PO2- group; to some extent five-membered chelates (Cu(PA)cl/O) involving the ether oxygen of the -CH2-O-CH2-PO2-3 chain are formed, and in all complexes an additional nucleobase-metal-ion interaction occurs. Based on 1H NMR line-broadening measurements and structural considerations it is concluded that in Cu(3-deaza-PMEA) the interaction occurs with N7 whereas in Cu(7-deaza-PMEA), Cu(1-deaza-PMEA), and Cu(PMEA) it occurs with N3. The proof of a metal ion-N3 interaction is important (and also of relevance regarding DNA) because so far this interaction has received little attention. In all Cu(PA) systems three major isomeric species are in equilibrium; for example, 17(∓3)% of Cu(PMEA) exists as an isomer with a sole Cu2+-phosphonate coordination, 34(∓10)% as Cu(PMEA)cl/O, and in 49(∓10)% the Cu2+ is bound to the phosphonate group, the ether O, and N3. In contrast, 54(∓8)% of Cu(5′-AMP) occurs as an isomer with sole Cu2+-phosphate coordination and 46(∓8)% as a macrochelate involving N7 too.
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    The Versatility of Lithium Reagents in Synthetic Organometallic Chemistry: Their differing reactions with [Cp*Mo(NO)(CH2SiMe3)2] (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1579-1587 
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    ISSN: 0947-6539
    Keywords: alkylidene complexes ; lithium ; molybdenum ; nitric oxides ; tungsten ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [Cp*Mo(NO)(CH2SiMe3)2] exhibits three principal types of reaction with the various lithium reagents investigated during this study, namely: regioselective deprotonation, reduction, and addition. Deprotonation of the reactant, achieved by treatment with lithium amide reagents, leads ultimately to the formation of the alkylidene „ate“ complex [Cp*Mo(NO)(CH2SiMe3)2(=CHSiMe3)]2-[Li2(thf)3] (1). While LiN(SiMe3)2 effects this conversion directly with no detectable intermediates, reaction with 1 equiv of LDA in THF for 15 min deprotonates the Cp* ligand to form the lithium salt of the „tucked-in“ ate complex [(η5,η1-C5Me4CH2)Mo(NO)(CH2SiMe3)2]-[Li(thf)3] (2) in 40% isolated yield. Complex 2 slowly converts to the thermodynamically more stable 1 when left as a THF or C6D6 solution at ambient temperature for 48 h. Reaction of the dialkyl starting material with either tBuLi or PhLi leads to the production of the alkylidene complex 1 in irreproducible yields (10-50% NMR; not isolable). A kinetic analysis of the reaction of [Cp*Mo(NO)(CH2SiMe3)2] with LiN(SiMe3)2 indicated that the reaction was first-order in both the lithium and molybdenum reagents, and the activation parameters of ΔH* = 7.3∓1.0 kcal mol-1 and ΔS* = - 34∓3 e.u. suggest an associative process. Treatment of the neutral dialkyl with 1 equiv of LiPPh2 in THF results in a one-electron reduction and production of {[Cp*Mo(NO)(CH2SiMe3)2[Li2(thf)3] (3). If left in solution, the 17e- dialkyl anion 3 is converted to the 18e- alkylidene anion 1 by the Ph2P-PPh2 coproduct, which effects the requisite hydrogen-atom abstraction. Finally, addition of a sterically undemanding alkyllithium reagent such as MeLi to the 16e- dialkyl reactant leads to the formation of the 18e- trialkyl anionic complex [[Cp*Mo(NO)(CH2SiMe3)2(=CHSiMe3)]2-[Li2(thf)3](Me)][Li(thf)3] (4). Warming of 4 in a C6D6 solution results in loss of methane and production of 1. In most cases, the chemistry exhibited by the Mo system is duplicated by the analogous W congener, [Cp*Mo(NO)(CH2SiMe3)2(=CHSiMe3)]2-[Li2(thf)3]. The solid-state molecular structures of complexes 1 and 4 have been established by single-crystal X-ray crystallographic analyses.
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    Cope Rearrangements versus Retro Diels-Alder ReactionsAzo Bridges from Azines, part 25; for part 24 see U. Brand, S. Hünig, K. Peters, F. Prokschy, H. G. von Schnering, Liebigs Ann. 1997, 785-789.Dedicated to Professor Dr. Dieter Seebach on the occasion of his 60th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1588-1599 
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    ISSN: 0947-6539
    Keywords: azo compounds ; cycloadditions ; hydropyridazines ; pyrazolines ; rearrangements ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two isomeric [4+2] cyclo-adducts from two different 1,3-dienes may result from direct cycloadditions as well as from Cope rearrangements (Scheme 1). This general question is tackled by employing two energetically different types of dienes, protonated pyrazolines (1H+, 2H+) or dihydropyridazines (3H+), prepared in situ from their trimers and alicyclic (4-6) or aliphatic (7-9) 1,3-dienes. Depending on structural features and conditions (amount of acid, reaction time), various ratios of the two isomeric [4+2] cycloadducts A and B are obtained; A and B are azo compounds 10, 14, 16, 20, 22, 24, 27, 32, 34, 36-39, 41, 42, pyrazolines endo-11, endo-13, endo-15, endo-endo-17, endo-18, endo-19, 21, 23, 25, 26, 28, and hydropyridazines 31, endo-33, endo-35, 40 and 43 (Schemes 3, 4). These results were backed by others from acid-catalyzed isomerizations, trapping experiments, and calculations of the equilibria (ΔΔH) between the isomers (by analogy with the corresponding olefins). A critical discussion reveals: a) Azo compounds 20, 22, 24, 27, 34, 38, and 42 must result from a [4++2] cycloaddition with inverse electron demand, whereas hydropyridazines endo-33, endo-35, 40, and 43 originate from a [4+2+] cycloaddition with normal electron demand. b) All isomerizations occur by a [3,3] sigmatropic rearrangement; [4+2] cycloreversion is energetically disfavored. c) A clear-cut distinction between the [4++2] or [4+2+] cycloaddition reaction routes to the energetically well-balanced systems 10→endo-11 and 12→endo-13 is not possible. d) The two cycloadditions may well favor a nonconcerted reaction through an allylic cationic intermediate which also governs the [3,3] rearrangements (Scheme 8).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031008
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    The Nature of the Metal - Silicon Bond in [M(SiR3)H3(PPh3)3] (M = Ru, Os) And the Crystal Structure of [Os{Si(N-pyrrolyl)3}H3(PPh3)3] (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1608-1616 
    Details
    ISSN: 0947-6539
    Keywords: ab initio calculations ; hydrides ; osmium ; ruthenium ; silicon ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The compounds [M(SiR3)H3(PPh3)3] (1: M = Ru, R = 1 - NC4H4 = pyr; 2a-c: M = Os, R = pyr, Et, Ph) are prepared through reaction of either [RuH2(PPh3)4] or [OsH4(PPh3)3] with the appropriate silane HSiR3 (3a-c: R = pyr, Et, Ph). The X-ray structure analysis of compound 2 a and ab initio calculations on the model compounds [Os(SiR3)H3(PH3)3] (4a-c: R = H, NH2, pyr) reveal a trigonal distortion along the Os-Si axis from an idealised tetrahedral geometry for the central OsSiP3 heavy-atom skeleton. The structure can be described as two face-shared octahedra, one based on osmium (OsH3P3) and the other based on silicon (SiH3N3). Studies of the bonding situation in 2 a reveal that the N-pyrrolyl substituents have a marked shortening effect on the osmium-silicon distance (229.3(3) pm) and that each of the three hydride ligands participates in partial three-centre bonding involving osmium, silicon and hydrogen. 1H, 13C, 29Si and 31P NMR spectra were used to determine the solution structures of complexes 1 and 2 a.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970031010
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    A Pyrrole-Imidazole Polyamide Motif for Recognition of Eleven Base Pair Sequences in the Minor Groove of DNADedicated to Dieter Seebach on the occasion of his 60th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1600-1607 
    Details
    ISSN: 0947-6539
    Keywords: DNA recognition ; hydrogen bonds ; ligand design ; molecular recognition ; sequence-specificity ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new upper limit of binding site size is defined for the 2:1 overlapped polyamide: DNA motif. Eight-ring polyamides composed of four-ring subunits containing pyrrole (Py) and imidazole (Im) amino acids linked by a central β-alanine (β) spacer („4-β-4 ligands“) were designed for recognition of eleven base pair sequences as antiparallel dimer (4-β-4)2.DNA complexes in the minor groove. The DNA binding properties of three polyamides, ImPyPyPy-β-PyPyPyPy-β-Dp, ImImPyPy-β-PyPyPyPy-β-Dp, and ImImImPy-β-PyPyPyPy-β-Dp, were analyzed by footprinting experiments on DNA fragments containing the respective match sites 5'-AGTAATTTACT-3', 5'-AGGTATTACCT-3', and 5'-AGGGATTCCCT-3' (Dp = dimethylaminopropylamide). Quantitative footprint titrations reveal that each polyamide binds its respective target site with subnanomolar affinity and 7-fold to over 30-fold specificity over double-base-pair mismatch sites. A 20-fold decrease in binding affinity is observed for placement of a side-by-side β-β pairing opposite G.C/C.G relative to placement opposite a A.T/T.A base pair. The use of side-by-side antiparallel β-alanine residues as an A.T/T.A-specific DNA binding element provides a new pairing rule for polyamide design. Expanding the DNA binding site size targeted by pyrrole-imidazole polyamides represents an important step in the development of cell-permeable synthetic ligands for the control of gene-specific regulation.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970031009
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    Masthead (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760010101
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    Abstracts of articles in this issue (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 2-2 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760010102
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  • 54
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    Effect of hydrostatic pressure on polyethylene melt rheology (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 14-20 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A description is given of the procedure and equipment used for the purpose of studying the effect of hydrostatic pressure upon the capillary flow properties of polymer melts. Flow properties are reported for a low density polyethylene over a wide range of temperatures, die sizes, different pressures and hydrostatic pressures.
    Additional Material: 12 Ill.
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    A study of the polymerization of thermosetting polymers by electrical resistivity techniques (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 3-8 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A study was designed to show the nature of weathering of an elastomer poly( ester-urethane), and to indicate methods of overcoining the deficiency. Unprotected polymer, when exposed to UV radiation in a Weatherometer, showed deterioration which is characterized by loss of tensile strength, some increase in modulus, and a decreased extensibility of surface skin.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760010103
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    Thermomechanical studies of amorphous and crystalline polymers (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 9-13 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Translated from: Vysokomolekuliarnye Soedineniia 2, 778-84 (May 1960). A thermomechanical study was made of the softening of crystalline polymers during uniform, uniaxial stretch and also of the effect of the rate of heating upon the softening or amorphous polymers. The effect of the tensile force on the thermo-mechanical behavior of various polymers was measured over the range 20 to 100 kg/cm2 and within wide temperature limits (-150° to 250°C). Ribbons 50 mm long, 2-4 mm wide and 0.05 to 0.5 mm thick served as specimens.
    Additional Material: 8 Ill.
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    Mechanisms of ultraviolet stabilization of plastics (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 26-30 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effectiveness of ultraviolet stabilizers of various types of polyolefin, cellulose ester, and poly (vinyl chloride) plastics was investigated. Most of these stabilizers were of the ultraviolet-absorbing type but two were of the nonabsorbing type. Exposures were made both outdoors and indoors in a Twin-Arc Weatherometer. The latter was modified by the addition of ten 20-watt fluorescent sun lamps to remedy the short-ultraviolet deficiency of the enclosed carbon arcs.
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    URL: http://dx.doi.org/10.1002/pen.760010107
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    Ultraviolet degradation of plastics and the use of protective ultraviolet absorbers (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 21-25 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The degradation of plastics by ultraviolet energy and the use of protective ultraviolet absorbers to improve stability necessitate studies along several lines. These include (a) the measurement of the ultraviolet spectral energy distribution of sunlight and of the indoor accelerated test sources, (b) the measurement of the extent of degradation as a function of the wavelength of the incident radiation, (c) an estimate of the absorbing effectiveness of the added protective agents, and (d) the stability of the protective ultraviolet absorbers themselves.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760010106
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    The effect of molecular weight distribution on the flow properties of polyethylene (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 40-46 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The non-Newtonian flow behavior of polyethylene has been investigated with respect to the effects of molecular weight and molecular weight distribution. Effects of die geometry on melt fracture as well as preliminary extrudate orientation studies are discussed.
    Additional Material: 16 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760010109
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    A study of the weathering of an elastomeric polyurethane (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 31-39 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A study was designed to show the nature of weathering of an elastomer poly(ester-urethane), and to indicate methods of overcoming the deficiency. Unprotected polymer, when exposed to UV radiation in a Weatherometer, showed deterioration which is characterized by loss of tensile strength, some increase in modulus, and a decreased extensibility of surface skin.
    Additional Material: 16 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760010108
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    Research is key to progress in the plastics industry (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 52-52 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760010111
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  • 62
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    Hydroxy alkyl phosphate esters as curing agents for epoxy resins (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 47-51 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new curing system which yields room temperature curing epoxy adhesives with high bond strength and softening point has been developed for service in contact with high explosives. Bisphenol A type resins cured with hydroxyl alkyl phosphate acid esters are used. Short pot life and relatively low alkali resistance are drawbacks of the system.
    Additional Material: 3 Tab.
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    Masthead (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760010201
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    Abstracts of articles in this issue (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 54-55 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760010202
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    How can scientists keep up with science? (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 56-56 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760010203
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    Cryogenic adhesive properties of bisphenol-A epoxy resins (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 73-79 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This article includes a comparison of the adhesive properties of bisphenol-A expoxides at 300°K and 76°K with respect to the molecular weight of the uncured resins. Joints of 2024 aluminum were tested at 300°K and 76°K in tensile-shear and in impact-shear, and total linear thermal contraction of the cured resins was measured between the two temperatures. Results are discussed with respect to residual joint stresses and adsorptive properties of the resins.
    Additional Material: 9 Ill.
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    A method for determination of maximum heat resistance of plastics (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 63-67 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new method for measuring heat stability and temperature of degradation of thermosetting plastics is described, as well as an improved method for the determination of transition temperature into glassy or viscous state for thermosetting resins. Magnitude of elastic deformation is tied in with length of polymer chain and lattice density.
    Additional Material: 11 Ill.
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    Dielectric properties of plasticized melamine resins (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 68-72 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: During the last thrity years, dielectric measurements have been employed extensively to provide a better understanding of the interactions between polymer and plasticizer in various thermoplastic formulations. Recently, a series of melamine resins, plasticized to the extent that shrinkage and internal stress were modified, became available. Since there is little information in the literature concerning the dielectric properties of such thermosetting resins, a study was made of the variation of dielectric constant and loss as a function of frequency and temperature.
    Additional Material: 16 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760010206
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    Some functions of 2-hydroxybenzophenones as weathering stabilizers for polymers (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 57-62 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Derivatives of 2-hydroxybenzophenone are well-known stabilizers for such polymers as cellulose acetate butyrate and polyesters. Their stabilization effectiveness is commonly associated with their ability to screen a polymer from the harmful ultraviolet radiation found in sunlight. They also satisfy other requirements for effective stabilizers, namely, compatibility with many polymers and an inherent stability to ultraviolet light. Several other functions of 2 hydroxybenzophenones in stabilizing a polymer to ultraviolet light have been postulated, but little experimental data related to them are available. This paper deals with some of the additional functions of 2-hydroxybenzophenones in weathering stabilization as investigated by nuclear magnetic resonance spectroscopy (NMR) and electron paramagnetic resonance spectroscopy (EPR).
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760010204
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    Electrical resistivity of polymers (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 80-85 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The magnitude and temperature dependence of the electrical resistivities of a number of thermoplastic and thermosetting high polymers have been determined. Activation energies for the electrical conduction process Ee have been calculated and found to vary from 12 to 60 Kcal/mole depending upon the structure of the polymer. Results are interpreted in terms of an ionic diffusion process and discussed in terms of the structure of the polymers.
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    Abstracts of articles in this issue (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 102-103 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760010302
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    Masthead (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760010301
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    Polyethylene flow data from melt viscometer and commercial extruder measurements (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 86-92 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: For broad ranges of operating conditions and a wide variety of high pressure polyethylenes, the flow data obtained from a high shear viscometer and a commercial extruder are identical. Discrepancies between flow data can result from non steady state viscosities in the high shear viscometer, or from cooled screw extruder operation. In the broad regions in which the flow data concur, the readily obtained viscometer data are suitable for predictions of extruder performance. The principle is illustrated by the good correlation of a viscometer flow curve parameter and the screw power consumption in the extruder. Principles outlined for flow data identity and extruder performance prediction are believed to be general, but the quantitative limits defined are specific to the extrusion devices involved.
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    An investigation of some variables affecting impact resistant thermoplastics (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 93-100 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Recent technology has evolved a number of dissimilar thermoplastics which under conditions of ambient temperature and impact loading show both the high modulus, which is mainly a property of brittle polymers in the glassy state, and also the impact resistance, such as may be expected of polymers in the rubbery state. Several of these special plastics were examined by electronmicroscopy and also with respect to several aspects of their mechanical behavior to establish by direct observation and inference whether or not different types of plastics exhibit some common features of structure which promote impact resistance. These observations suggest the hypothesis that special circumstances of domain heterogeneity can override many other variables of composition or molecular structures in controlling the fracture mechanism.
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    Best of ANTEC - SPE Transactions (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 104-104 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760010303
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    Thermodynamic diagrams for polyethylene resins (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 105-108 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: For resins of room temperature density 0.91 to 0.96 g/cc, enthaply and internal energy diagrams have been developed from 0 to 200°C and up to 1000 atmospheres. These diagrams can be used for estimating properties for which data are not available, and provide unified view of many properties of polyethylene under conditions of fabrication and use. Extent of crystallinity estimates can be made from enthalpy, internal energy, specific volume, compressibility and melting point data provided for hypothetical amorphous, crystalline and actual resins.
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    The strength of glassy polymers (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 109-112 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The Griffith theory for brittle fracture predicts that the tensile strength should be inversely proportional to the square root of the size of a defect or flaw in the sample tested. The validity of this relation has been investigated for the glassy polymers, poly(methyl methacrylate) and polystrene. The results indicate that the strength of the polymers depends on two factors: (1) the surface energy, and (2) the inherent flaw size. The surface energy is primarily that dissipated in a viscous flow process and the inherent flaw size is related to the tendency of the polymer to craze under stress.
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    The effect of extrusion variables on the fundamental properties of tubular polythene film (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 121-132 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The mechanism of formation of tubular polythene film is a complicated process, and extensive studies have shown that the properties of the film made are influenced profoundly and in a complex way both by the processing conditions used by certain design features of the equipment. Studies of the effect of the extrusion variables on the more important film properties, both optical and mechanical, are reviewed in this paper. The results are discussed in terms of the fundamental nature of polythene film, its surface, its crystalline structure and its orientation.
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    Flow patterns in a non-Newtonian fluid in a single-screw extruder (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 113-120 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Flow patterns in the channel of a screw extruder have been investigated in a study utilizing a model extruder with stationary screw and a rotating, transparent barrel. Photographs of flow streamlines at conditions over the full range of output restriction are presented for a non-Newtonian fluid. A technique employing photographs of particle tracers was used with the same apparatus to permit quantitative measurement of velocity profiles with both a Newtonian and a non-Newtonian fluid.
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    Inorganic-organic high polymers, phenoxyaldehyde resins of Titanium (IV) and Hafnium (IV) (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 139-142 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new series of inorganic-organic high polymers have been synthesized namely; the metaloxene polymers of phenolaldehyde. Titanium (IV), Zirconium (IV) and Hafnium (IV) phenolaldehyde have been prepared and other metals especially the refractory type metals may merit further development as calorobic plastic materials. The hafnium resin has been compression molded into a rocket-nozzle insert shape with satisfactory rocket-firing results.
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    New frontiers in the field of macromolecules (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 147-148 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760010311
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    Resins from cyclohexene oxide derivatives and fatty acids (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 143-146 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This article describes preparation of resins as described in the title above, and the effect of concentration of the diepoxide, dimer acid, and initiator (stannous octoate). Proportion of dimer acid and diepoxide has a marked influence on hardness and tensile properties of resins. Change in tensile properties upon aging correlates very well with change in hardness. Higher proportions of dimer acid produce softer, more flexible resins. The resins have unique electrical properties at temperature up to 175°C, apparently because of the high proportion of hydrocarbon in the resin.
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    Masthead (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760010401
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    Effect of gamma radiation on chemical structure of plastics (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 133-138 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Twelve plastics representing various chemical structures were studied as part of a program to determine the utility of plastics as packaging materials in the high radiation presentation of food. The plastics were exposed to selected dosages of Cobalt-60 gamma radiation in vacuum and in air. Gas evolution and changes in infrared spectra as a result of irradiation were used to hypothesize the relative stability of these plastics to irradiation. Based on these facts it was found that plastics containing conjugated ring systems, ionic linkages, and chlorine in side groups were the most stable.
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    Abstracts of articles in this issue (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 150-151 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760010402
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    First year for spe transactions (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 152-152 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760010403
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    An empirical method for … The prediction of liquid permeation in polyethylene and related polymers (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 153-163 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Permeability properties depend on the size, shape and polarity of the permeating molecule. Permeability of organic liquids, polar or non-polar, can be quite accurately predicted if the chemical composition of the permeant is known. By the choice of an arbitrary value (unity) as an indicator for the carbon atom, numbers specific to each structural element of the permeating molecule can be computed from previous experimental data. These numbers, herein called “Permachor” values (π), then combine by simple addition to relate the logarithm of a liquid's permeation in polyethylene.
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    Polymers as conductors and semi-conductors (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 169-176 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Mobile ions can be introduced thereby increasing the conductivity, with a limiting operating temperature range of 200°-250°C. Conductivity can be increased with the formation of conjugatd double bonds. Polymeric compounds may be synthesized with metallocyclic groups, where an atom of metal is bound to nitrogen atoms in a heterocyclic system in the basic chain of conjugation of the macromolecule. Here phtalocyanimes possess the greatest thermal stability. Lastly there are semiconducting polymers with conjugated double bonds containing hetero-atoms in the principle chain, having unpaired electrons of oxygen and nitrogen.
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    The thermodynamics of biaxial elongationSupported in part by a contract from the Office of Naval Research and in part by: grants from the National Science Foundation, the Plax Corporation and assistance from the Monsanto Chemical Company. (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 164-168 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: If temperature variations of forces in both directions are observed simultaneously at constant simple dimensions, internal energy and entropy changes on elongation in those directions may be calculated at constant volume and in the more common experimental condition of constant pressure. Thermodynamic derivatives at constant volume are important for fundamental molecular interpretation being related to configuration change. Constant pressure quantities were therefore changed into constant volume ones by the use of an evaluated correction term, involving average Young Moduli and thermal expansion coefficient.
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    Dynamic measurement of mechanical moduli I (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 177-179 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Equipment is described for measurement of Young's and shear modulus on the same identical polymer sample, by a free-vibration method. Strain gauges are used as sensors in an automatic recorder. Young's modulus and damping, shear modulus and damping and Poisson's ratio are reported over a range of temperature for polypropylene, Nylon 66 and poly (methylmethacrylate). It is found that Poisson's ratio shows a dip in the glass transition region and that values greater than the infinitesimal strain limit of 0.5 are obtained in the rubbery region.
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    An introduction to the glass-resin interface section (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 180-180 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760010408
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    Physical techniques used in studying interfacial phenomena (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 181-190 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Adsorption studies on powdered and planar surfaces yield significant information regarding the rate and degree of interaction between the substrate and the organic adsorbate. Investigative tools include contact angle measurement, radiotracer methods, ellipsometry, x-ray diffraction, electron diffraction, elegant infrared techniques, dynamic desorption techniques, and film balance applications.
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    A study of the finish mechanism: Glass to finish, finish thickness and finish to resin (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 214-223 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A solution of substituted alkyl alkoxy silanes was applied to E-glass filament strands before forming glass-resin composite hoops, which were tested to relate changes in hoop physical properties to the nature of the coupling agent-size application. Continuously heat cleaning E-glass in oxygen-enriched air gives a strand that, when properly coated with size and laminated, makes a hoop with superior strength and modulus properties.
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    A new interpretation of the glass-coupling agent surface through use of electron microscopy (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 224-233 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Theoretically a monolayer or insignificant weight per cent of coupling agent should give optimum properties for fiber glass-resin composites, contrary to commercial practice. Studies of variation of chemical bonding between the coupling agent and the resin and the study of the degree of bonding of the coupling agents to the glass by extraction techniques have not explained this effect. However, new techniques of electron microscopy have revealed details of loading distribution and agglomeration on the glass fiber which tend to explain this effect.
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    The chemistry of chromium complexes used as coupling agents in fiberglass resin laminates (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 199-213 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The chromium complex is chemically bonded by ion exchange with alkali cations to strongly acidic sites in the glass surface. These sites are formed by the isomorphous replacement of silicon by boron and aluminum in the network structure. Polymerized complexes are better bonding agents than monomeric ones. Specific interactions between organic groups on the chrome complex and the bonding resins also determine laminate strength and water resistance.
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    Study of the interaction of organic monomers and water with fiberglass by Sorption methods (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 191-198 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Interfacial reactions between organosilane-treated fiberglass and styrene, and bond conditions in these and in polymerized ethylene oxide and epichlorhydrin-E-glass systems were investigated. The vinyl functionality of some alkenylsilanes showed little effect on the polymerization of styrene on E-glass. The polymerization of this aromatic monomer on vinyltrichlorosilane-reacted fiberglass did not result in interfacial bond formation. Sorption of water on organosilane-coated glass at different temperatures suggested that permeation of the adsorbate into the bulk of the substrate was determined by diffusive transfer of water molecules.
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    Masthead (1962)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 2 (1962) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760020101
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    The degree of bonding between coupling agents and glass filaments ¨ a study ¨ (1961)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 1 (1961), S. 234-244 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Evidence indicates that there is a chemical bond between the coupling agent of either silane or chrome complex type and the glass substrate, but that this chemical bond may be strong or weak, depending on the elements making up the bond and the other elements in the immediate area surrounding the bond. These elements can exert either a beneficial or detrimental effect on the strength of that bond. Other evidence is given to show that a vapor phase treatment that applies silane coupling agents like A-1100 to “E” glass gives the highest known strength retention values. A mechanism is advanced to explain the bridging of unreactive sites on glass surfaces by silane coupling agents applied from solution.
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    Abstracts of articles in this issue (1962)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 2 (1962), S. 2-4 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760020102
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    Crystallization kinetic studies of vinylidene chloride-alkyl acrylate copolymers by torsional measurementsPresented at the 140th National Meeting of the American Chemical Society, Chicago, Illinois, September 3-8, 1961. (1962)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 2 (1962), S. 7-10 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: By following the changes in torsional modulus as a function of time, the kinetics of crystallization of three copolymers of vinylidene chloride containing 10% mole % alkyl acrylate were investigated and the geometrical growth and nucleation constant of the Avrami equation was determined. Isotherms were superimposable within certain temperature ranges while the nucleation constant decreased with a decrease in temperature. Rate of crystallization increased with increase of the alkyl side chain length.
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