Distribution of Substituents in Methylcellulose

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Abstract
The distribution of methyl groups in methylcelluloses (DS 1.7) has been determined. The partially methylated monosaccharides obtained on complete hydrolysis of methylcellulose were converted into alditols by reduction. They were identified as their acetates or trimethylsilyl ethers by gas-liquid chromatography-mass spectrometry and quantified by gas-liquid chromatography. In addition, 13C-nuclear magnetic resonance spectra of native and hydrolyzed methylcelluloses as well as the partially methylated alditols obtained by hydrolysis and reduction were analyzed. The main glucose methyl ethers obtained were in decreasing order 2,6-, 2,3,6-, 2-, 6-, and 2,3-. The 2-and 6-positions were occupied by methyl groups in 70.0 and 61.5%, respectively, while the 3-position contained only 37.4%. The GLC-MS method gave a more accurate determination of the distribution of methyl groups in methylcellulose compared to NMR spectroscopy.