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  • 1
    Electronic Resource
    Electronic Resource
    High-resolution solid-state carbon-13 nuclear magnetic resonance study of chitin (1990)
    s.l. : American Chemical Society
    Macromolecules 23 (1990), S. 3576-3583 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00217a008
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  • 2
    Electronic Resource
    Electronic Resource
    Cellulose organic solutions: A nuclear magnetic resonance investigationPart of this work was presented at the Symposium on “New Solvents of Cellulose” at the ACS Meeting, Chicago, August 23, 1977. (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 13-25 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four solvents of cellulose have been studied by using 13C-NMR spectroscopy. All these solvents, N-methyl morpholine-N-oxide, methylamine, hydrazine, and paraformaldehyde (PF), contained dimethyl sulfoxide (DMSO) as a cosolvent. Oligomers of cellulose of DP = 10 soluble in hot DMSO have been used as model compounds. 13C chemical shifts and line shapes show that three of the mentioned solvents are “true solvents” of cellulose. On the other hand, dissolution of cellulose in DMSO-PF system occurs by the formation of a statistical derivative of cellulose. Enriched 13C bacterial cellulose on C-1 and C-6 positions have been used to identify the 13C positions mainly in DMSO-N-methyl morpholine-N-oxide system. This solvent has been found to be degradative for the macromolecule when the solution is kept at 100°C over a long period. Viscosity measurements show a reduction of the molecular weight in these conditions. Polarimetry indicates that no glucose is present in solution and hence there is a statistical break of the chain. Enriched cellulose solution in DMSO-N-methyl morpholine-N-oxide has been also used for relaxation time (T1) determination both of the solvent and of the enriched carbons of the polymer. Nuclear Overhauser enhancement (NOE) was found to be 1.8 for C-1 and 2.1 for C-6 showing that relaxation phenomenon is not purely dipolar. T1 values of 97 and 65 msec are found for C-1 and C-6 of cellulose, in good agreement with the values known for polysaccharides. Determination of T1 for the different carbon atoms of the solvent DMSO-N-methyl morpholine-N-oxide with and without cellulose shows a large reduction of T1 for N-methyl morpholine-N-oxide molecule. This denotes a slower molecular motion of this molecule and a preferential interaction with the cellulose macromolecule.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.170180102
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  • 3
    Electronic Resource
    Electronic Resource
    NMR studies of chitin and chitin derivatives (1982)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 593-601 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The 13C NMR spectra of N-acetyl-D-glucosamine (1) and chitobiose (2), monomer and dimer of chitin, were assigned and used to assign the 13C NMR spectra of chitin in lithium thiocyanate and in LiCl/dimethylacetamide solutions. The dissolution of chitin in formic acid was studied. IR, 13C and 1H NMR spectra show that dissolution occurs by a reaction of formic acid with chitin with the formation of formyl chitin as a statistical derivative of chitin. 13C NMR spectra of diformyl- and diacetylchitin were also assigned to characterize these regular polymers.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1982.021830309
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  • 4
    Electronic Resource
    Electronic Resource
    Conformational analysis of ß(1→4)-linked polysaccharides in aprotic solvent solutions (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 153-162 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The 1H NMR parameters (chemical shift and coupling constant) of ß(1→4)-linked polysaccharides xylan, cellulose, and chitin are compared in solutions of aprotic solvents. The following NMR parameters are analyzed: (1) Chemical shifts of labile protons, (2) their variation with temperature, (3) coupling constants through the H—C—O—H moiety  -  for monomers, dimers, and the corresponding polymers. It is observed that the OH-3 hydroxyl group for cellulose and chitin oligomers and polymers present a particular behaviour, which is in agreement with the existence of an intramolecular hydrogen bond between this hydroxyl of one monomeric unit, and the heterocyclic oxygen atom of the adjacent monomeric unit. This kind of intramolecular hydrogen bond is not observed in case of the xylan series. It can be concluded that substitution of an equatorial hydrogen atom at the C-5 position of the sugar ring by a CH2OH group  -  when passing from xylan to cellulose and chitin  -  induces a rotation restriction around the glycosidic bond. This places the OH-3 hydroxyl group in a favourable position to be hydrogen-bonded. The consequent implication on the respective conformations of the chains in solution is discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1988.021890115
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  • 5
    Electronic Resource
    Electronic Resource
    1H NMR study of the chitin dissolution mechanism (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 1787-1795 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The 1H NMR spectra of N-acetyl-D-glucosamine (1) and methyl-B-D-chitobioside (2), the monomer and dimer of chitin, respectively, were determined in the aprotic solvents, N,N-dimethylacetamide (DMA) and DMA containing lithium chloride. It could be shown that dissolution of 1 and 2 in DMA/LiCl proceeds via interaction of one LiCl molecule with each labile proton (OH or NH). Observation of the temperature-dependent hydroxyl proton chemical shift revealed the particular behaviour of the OH3 hydroxyl of 2. This dependence was assigned to the existence of an intramolecular hydrogen bond between OH3 and O5′ (the heterocyclic atom) of the other D-glucopyranosyl unit. Similar results were found for chitin in DMA/LiCl solution.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1985.021860907
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  • 6
    Electronic Resource
    Electronic Resource
    Xylan derivatives: aromatic carbamates (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 321-328 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Xylan, which is a natural polysaccharide extracted from plant cell walls, is a branched polymer. Linear xylan can be easily obtained through preferential cleavage of the branched sugar units. Xylan is a polyhydroxylated polymer, which is difficult to dissolve in classical organic solvents. The complete substitution of the hydroxyl groups regularly distributed along the xylan chain has been achieved via their reaction with aromatic monoisocyanates. Xylan-2,3-bis(phenyl carbamate) (5) and xylan-2,3-bis(tolyl carbamate) (6) were obtained with good yield. They were fully characterized by using spectroscopic methods (IR, 1H and 13C NMR). These new xylan derivatives are thermoplastic at high temperatures and decompose beyond 300°C.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940128
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  • 7
    Electronic Resource
    Electronic Resource
    Structural and conformational investigation of carrageenans (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2165-2175 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A detailed assignment of the 13C chemical shifts of κ- and ι-carrageenans in their Na+ and K+ forms in D2O and dimethylsulfoxide is given. Evidence of the conformational transition induced by temperature variation in the absence of any gel formation on κ-carrageenans is also presented. This evidence is based on 13C-nmr and optical rotation experiments.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360191203
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  • 8
    Electronic Resource
    Electronic Resource
    13C-NMR spectroscopic investigation of α- and β-1,4-D-glucose homooligomers (1979)
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 167-185 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A complete, unambiguous assignment of all the 13C signals of cellobiose and maltose has been achieved using methods such as selective proton decoupling, 13C selective spin labeling, and isotopic chemical shift induced by deuterium. The chemical-shift variation of the 13C signals with the degree of polymerization in each α or β (1 → 4) series is discussed. The chemical-shift dependence on temperature and solvent in these two series is shown and interpreted in terms of modifications of the solvation and of the conformation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1979.360180113
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  • 9
    Electronic Resource
    Electronic Resource
    Biosynthèse de la cellulose bacterienne deutériée: étude par R. M. N. du taux d'incorporation et de la localisation du deutérium (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2269-2273 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of the NMR spectra (250 MHz) of cellulose triacetate allows the determination of the percentage of deuterium bonded to each of the six carbon atoms of the monomer residue (except for H-1 and one of the protons bonded to C6 where the signals overlap). Deuterated derivatives of D-glucose and/or deuterated water were used for the biosynthesis of bacterial cellulose by Acetobacter xylinum. Analysis of NMR spectra of acetylated samples gives the following results. About 90% of the protons linked to C1 and C6 come from the D-glucose used in the nutrition medium, whereas 10% are exchanged with other sources of protons. Over 40% of the protons linked to C2, C3, C4, and C5 arise from the water of the nutrition medium. Discrepancies between results of biosynthesis from deuterated water and from deuterated D-glucose can only be explained if more than one enzymatic process is involved in the biosynthesis of bacterial cellulose.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360101118
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  • 10
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    High-resolution solid-state carbon-13 nuclear magnetic resonance study of chitin (1990)
    American Chemical Society
    Details
    Publication Date: 1990-07-01
    Print ISSN: 0024-9297
    Electronic ISSN: 1520-5835
    Topics: Chemistry and Pharmacology , Physics
    Published by American Chemical Society
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