Analysis of the 13C-n.m.r. spectra of hydrolyzed and methanolyze O-methylcelluloses: monomer compositions and models for their description

✍ Scribed by Jacques Reuben

• Publisher: Elsevier Science
• Year: 1986
• Tongue: English
• Weight: 663 KB
• Volume: 157
• Category: Article
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(86)85069-8

✦ Synopsis

Complete assignments are presented of the 13C-n.m.r. spectra of the mixtures of methylated D-glucoses and methylated methyl D-glucosides that respectively result from hydrolysis and methanolysis of commercial samples of O-methylcellulose. The effects of methylation on the 13C chemical shifts of some of the atoms deviate from additivity, indicating interaction between the substituents at C-l, -2, and -3 of the D-glucopyranose ring. The monomer composition (given by the mole fractions of the component monosaccharides) conforms to a statistical, kinetic model that assumes that the reactivity of the 3-hydroxyl group depends upon the state of substitution at C-2. The relative rate-constants (averaged over the two samples) of the hydroxyl groups in the methylation reaction are k2: k,:k$ k, = 1.24:0.28:0.82:1.00, indicating that the reactivity of OH-3 increases threefold upon methylation of OH-2.