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  • Chemistry  (83)
  • Polymer and Materials Science  (37)
  • Debittering  (3)
  • F10
  • 1990-1994  (86)
  • 11
    Electronic Resource
    Electronic Resource
    Reactivity of Dithiazinanes towards BH3, BD3 and BF3. New Heterocycles: 5,5-Dimethyl-1,3-dithia-5-azonia-4-boratacyclohexane and 6,6-Dideuterio-5-methyl-5[D1]methyl-1,3-dithia-5azonia-4-boratacyclohexane. A Method for the Dimethylation and Monodeuteriomethylation of Primary Amines (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 863-867 
    Details
    ISSN: 0009-2940
    Keywords: Dithiazinanes ; Dithiazoniaboratacyclohexane ; Amines: dimethylation and monodeuteriomethylation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 5-Methyl-and 5-tert1-butyl-1,3,5-dithiazinane (1 and 7) react with BH3·THF, and Et2O·BF3 to yield the N1-coordinated adducts 2 - 4 (with BH3, BD3, and BF3, respectively). The conformations and spectroscopic properties of the adducts are discussed. The reactions of 1 and 7 with BY3·THF lead to the six-membered boron heterocycles 5,5-dimethyl-1,3-dithia-5-azonia-4-boratacyclohexane (5), 4,4-dideuterio-5-methyl-5[D1]methyl-1,3-dithia-5-azonia-4-boratacyclohexane (6), and 5-tert1-butyl-5-methyl-1,3-dithia-5-azonia-4-boratacy-clohexane (8). Compounds 2 and 5 are isolobal isomers. The reaction of BH3 or BD3 with 7 affords, after heating, tert1-butyldimethylamine - borane (9) and tert1-butyldi([D1]methyl)1-amine - trideuterioborane (11), respectively. The dithiazinane derivatives may be used in organic synthesis for the dimethylation of primary amines and the preparation of alkyldimethylamines with monodeuterated methyl groups.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260403
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  • 12
    Electronic Resource
    Electronic Resource
    From Azole - Borane Adducts to Azaboles  -  Molecular Structure of an Imidazabole (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 343-346 
    Details
    ISSN: 0009-2940
    Keywords: Azole-borane adducts ; Azaboles ; Imidazabole ; X-ray analysis ; NMR, multinuclear ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Elimination of H2 from the imidazole - borane adduct 1 leads to a mixture of the imidazaboles 2 and 2′. The symmetrical isomer 2 (two H2BNC fragments) is isolated in pure state and characterized by an X-ray structure analysis (monoclinic, space group P21). 2-(Trimethylstannyl)thiazole (3a) and 1-methyl-5-(trimethylstannyl)-1,2,4-triazole (3b) react with triethylborane to form adducts 4 from which, in the presence of an excess of Et3B, tetraalkyltin is elimated to give the thiazabole 5a and the triazabole 5b, respectively. Multinuclear 1H-, 11B-, 13C-, 14N-, and 119Sn-NMR spectroscopy serve for following the reactions (compounds 3 to 5) and to characterize all final products.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270210
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  • 13
    Electronic Resource
    Electronic Resource
    Theoretical approach to cationic polymerization of alkenylfuranes (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 281-287 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecular species proposed for the initial steps in the cationic polymerization of alkenylfurans were modeled by MNDO theoretically fully optimized structures. It was confirmed that the anomalous reactivity of ring C-5 of the monomers is determined by HOMO electron densitites, whereas calculated proton affinities from the semiempirical heats of formation fail to explain the low temperature experimental behavior of 2-vinylfuran (1c) from the point of view of stability of intermediate species. However, ab initio 4-31G calculations of proton affinities agree with the experimental facts and allow further explanations of the reactivity of furan derivatives in electrophilic media.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1990.021910202
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  • 14
    Electronic Resource
    Electronic Resource
    Blends of poly(hydroxy ether of bisphenol-A) with poly(2-vinylpyridine) and poly(4-vinylpyridine) (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 501-510 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(hydroxy ether of Bisphenol-A), so-called Phenoxy resin (structure-based IUPAC name: poly[oxy(2-hydroxytrimethylene)oxy-1,4-phenyleneisopropylidene-1,4-phenylene]), is shown to be miscible with poly(4-vinylpyridine) (P4VPy, poly[1-(4-pyridyl)ethylene]) and poly(2-vinylpyridine) (P2VPy, poly[1-(2-pyridyl)ethylene]) over the entire composition range. Miscibility of the blends is evidenced by their glass transition temperatures being intermediate between the pure polymers for the blends of P4VPy and Phenoxy but being higher than the average for the case of the P2VPy/Phenoxy blends. Hydrogen bonding between the components was detected through infrared spectroscopy, which was also used in the study of mixtures of low-molecular-weight analogues, in order to calculate the free energies of mixing according to the association model of Painter and Coleman.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940213
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  • 15
    Electronic Resource
    Electronic Resource
    Acetylene-terminated amide oligomers (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 953-962 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Six new acetylene-terminated (AT) oligomers were synthesized by reaction of 3-ethynylbenzoyl chloride and 4-ethynylbenzoyl chloride with three aromatic diamines containing four aromatic rings. The functionalization led quantitatively to AT oligomeric diamides of well defined composition, as confirmed by IR, 1H NMR and 13C NMR spectroscopy. The materials exhibited comparatively high melting points, over 200°C; thus, heating promoted curing before melting or simultaneously with melting, with the only exception of one sample that could be isolated in the amorphous state. Heating at 325°C led to insoluble cured materials, with excellent thermal resistance and glass transition temperatures Tg around 300°C.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940318
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  • 16
    Electronic Resource
    Electronic Resource
    Composites from furfuryl alcohol and inorganic solids by cationic initiation, 2Part 1: cf. ref.1.. Spectroscopic studies of poly(furfuryl alcohol)-silica composites obtained by trifluoroacetic acid initiation (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 1537-1544 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Furfuryl alcohol polymerizes in a suspension of dispersed inorganic solids such as silica in 1,2-dichloroethane using trifluoroacetic acid as initiator. Depending on the experimental conditions the reactions load to (1) agglomeration of particles, (2) composite and soluble polymer formation, (3) composite formation. The chemical structure of the soluble polymers is not regular but the furfurylic sequence is predominant. The polymer grafted on the surface of the solid is a strongly reticulated poly(furfuryl alcohol), which also possesses conjugated double bonds that are involved in an acid-base equilibrium with trifluoroacetic acid.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940602
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  • 17
    Electronic Resource
    Electronic Resource
    Polymerization of furfuryl alcohol with trifluoroacetic acid: the influence of experimental conditions (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 1-9 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Furfuryl alcohol was polymerized by trifluoroacetic acid in methylene chloride to give a colored polymer. This polymer possesses two main sequences in which the furan rings are connected by methylene groups (sequence 1) or by dimethylene ether groups (sequence 2). The polymer is not linear but highly branched, as detected by 1H and 13C NMR spectroscopy. Variations of the experimental conditions, such as the presence of air, the trifluoroacetic acid concentration, the reaction temperature and the solvent, do not allow a significant increase in the linear structure of the polymer. However, an increase in the acid concentration or an increase in temperature produce a decrease in the ether-bridged structure (sequences 2).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1992.021930101
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  • 18
    Electronic Resource
    Electronic Resource
    Polymer precursor synthesis of alumina fibers (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 495-503 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High strength alumina fibers were fabricated with a polymer precursor process which was monitored with 13C-NMR, elemental analysis, gas evolution, SEM, and X-ray diffraction. Methylaluminoxane was chain extended by reaction with H2O, the unreacted methyl groups were converted to propanoyloxyl and i-propanoyl groups in molar ratios of 0.2 : 0.8 to 0.4 : 0.6 to afford spinning dope of adequate fluidity which can be spun into filaments with suitable stability. These precursor fibers were hydrolyzed in two stages at ambient temperatures and at 320-350°C, and then calcined at 950°C. The resulting alumina fibers have average tensile strengths up to 1.1 GPa and modulus of greater than 140 GPa.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1991.080290406
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  • 19
    Electronic Resource
    Electronic Resource
    Stereoselective nucleophilic substitution of poly(vinyl chloride) with sodium thiophenate in cyclohexanone solution: Influence of the reaction temperature on the mechanism (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 99-104 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nucleophilic substitution of PVC with sodium thiophenate was carried out in cyclohexanone solution at 5, 25, 40, 60, and 70°C. The initial rate obeys an Arrhenius law from 25 to 60°C, with an activation energy of 70 kJ/mol. Conversion limits are observed which strongly depend on the temperature. The stereoselectivity of the reaction with respect to the configurational triads does not depend on the temperature: the distribution of configurations is only dependent on the conversion. Assuming an SN2 substitution mechanism governed by steric factors, the Monte Carlo simulation procedure described in a prior study is shown to give a good account for all temperatures above 40°C assuming for the mm, mr or rm, and rr triads a reactivity such as Rmm = 2 Rmr and Rrr nil at low temperature and very low at temperatures ≥ 40°C. The low conversion limits observed at 5 and 25°C cannot be explained by a limited accessibility of a part of the polymer. Finally, it is shown that the elimination reaction, which remains limited, does not interfere with the substitution process.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080300112
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  • 20
    Electronic Resource
    Electronic Resource
    Theoretical approach to cationic polymerization of alkenylfurans. II. Ab initio and semiempirical study of relevant steps in the reaction mechanism (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 2497-2502 
    Details
    ISSN: 0887-624X
    Keywords: ab initio ; AM1 ; cationic polymerization ; reaction mechanism ; furans ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: SCF ab initio and AM1 semiempirical calculations with full geometry optimization have been carried out to model the initial steps of alkenylfuran cationic polymerization. Semiempirical procedures have been used to model propagation steps. Proton affinities of the relevant neutral species as well as the heats of formation of probable dimers were calculated. The results allow the explanation of the experimental behavior. The capabilities of the employed methods to describe these type of processes is discussed. It is confirmed that competition between vinyl and ring site attacks is the most important feature in these systems. © 1992 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080301203
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