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  • 1
    Electronic Resource
    Electronic Resource
    Influence of anionic form on thermal degradation of TMAHP-cellulose (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 30 (1985), S. 4707-4711 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: Trimethylammoniumhydroxypropyl (TMAHP)-cellulose in 10 anionic forms (F-, Cl-, Br-, I-, HSO4-, NO3-, OH-, HCO3-, H2PO4-, CH3COO-) was prepared, and the influence of each anion on thermal degradation in inert atmosphere was studied. With the help of dynamic and isothermal thermogravimetry (TG) it was found that H2PO4- ions had the greatest retarding effect on TMAHP-cellulose degradation. From the values of rate constants it can be seen that all ionic forms of TMAHP-cellulose have the starting rate of thermal degradation greater than unmodified cellulose. The calculated values of activation energy of thermal degradation for different ionic forms are decreasing in following sequence: H2PO4- 〉 F- 〉 NO3- 〉 I- 〉 Br- 〉 HCO3- 〉 Cl- 〉 HSO4- 〉 OH- 〉 unmodified cellulose 〉 CH3COO-. From the results of pyrolyse measurements in combination with gas chromatography and mass spectrometry (Py-GC-MS) it follows that the products of the elimination of quarternary ammonium salts are trimethylamine, 3-hydroxy-2-propanone, and, in the case of OH- form, water. In all other ionic forms the third product is the corresponding acid.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1985.070301217
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  • 2
    Electronic Resource
    Electronic Resource
    Fast atom bombardment and collisional activation mass spectrometry of oligosaccharides related to xylans (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 17 (1988), S. 455-458 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The positive ion fast atom bombardment (FAB) mass spectra of oligosaccharides related to D-xylan and D-glucurono-D-xylans were investigated. Although the mass spectra of the underivatized oligosaccharides are relatively weak, they still offer reliable information on the molecular weight of these compounds from their [M + H]+ and [M + H + glycerol]+ ions. Esterification, glycosidation and/or partial methylation improve the relative abundances of the molecular and fragment ions with respect to those of the glycerol matrix. The mass spectra of these derivatized compounds also allow the determination of the mass of the monosaccharide units by the occurrence of more abundant and characteristic fragment ions. The differently linked D-xylobioses of the (1 → 2), (1 → 3) and (1 → 4) type cannot be distinguished on the basis of their mass spectra alone. The collisional activation (CA) spectra of the [M + H + glycerol]+ adduct ions, however, revealed that an unequivocal determination of the type of linkage in these isomers is possible. The small values of the discrepancy factors in the FAB CA spectra prove that CA mass spectrometry is, also in combination with FAB ionization, the most precise of the current mass spectrometric techniques.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200170607
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  • 3
    Electronic Resource
    Electronic Resource
    Electron impact, chemical ionization and collisional activation mass spectrometry of methyl O-acetyl-β-D-xylopyranosides (1985)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 12 (1985), S. 49-58 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectrometric behaviour of methyl O-acetyl-β-D-xylopyranosides has been studied using electron impact, methane and ammonia chemical ionization and collisional activation mass spectrometry. Based on this study the fragmentation of the compounds studied has been described. The structures of ions occurring after elimination of ketene in the fragmentation reactions of acetylated saccharides were studied by using the MNDO semi-empirical quantum chemical method. Calculated geometrical parameters (bond lengths, bond and torsional angles), distribution of net atomic charges and the difference in heat of formation (70 kJ mol-1) between the keto and enol isomers of [C5H7O3]+ ions studied predict that the enol structure is more stable thermodynamically than its corresponding keto isomer.The electron impact and chemical ionization mass spectra do not provide complete information for determination of the location of acetyl groups in methyl O-acetylpentopyranosides. The number and position of the acetyl groups however, can be determined unambiguously from collisional activation mass spectra of the [M - OCH3]+ ions. The reproducibility of the mass spectral data, obtained by the applied mass spectral methods was evaluated by calculation of discrepancy factors. From this point of view the collisional activation method is approximately five times more precise than electron impact and 10 times more precise than chemical ionization methods.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200120202
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal degradation of cellulose model compounds in inert atmosphere (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 31 (1986), S. 2433-2441 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: Thermal degradation of cellulose model compounds was studied using thermogravimetry (TG), electric spin resonance (ESR) spectroscopy, and gas chromatography-mass spectrometry (GS-MS). The molecular weight of samples did not influence the activation energy of gasification. In the case of catalytic influence of NaOH on cellulose thermolysis formation of gaseous products in the temperature range 250-350°C increased and a greater amount of residue was formed at 350-400°C compared to noncatalytic thermolysis. Residues of compounds with hemiacetal groups showed higher concentration of unpaired electrons than residues obtained from models with the blocked hemiacetal group.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1986.070310804
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  • 5
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    Low Temperature Thermolysis of Lignins - I. Reactions of ß—O—4 Model Compounds (1983)
    De Gruyter
    Details
    Publication Date: 1983-01-01
    Print ISSN: 0018-3830
    Electronic ISSN: 1437-434X
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by De Gruyter
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