DISTRIBUTION OF METHOXYL AND URONIC ACID GROUPS IN CEREAL STRAWS

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Abstract
The distribution of methoxyl and uronic acid groups in wheat and oat straw was investigated in the following successive fractions: extractive-free straw, pectin-free straw, holocellulose, hemicellulose "A", hemicellulose "B", and "alpha-cellulose" residue. About 18% of the total methoxyl content of extractive-free straws was found in the holocellulose fraction, the remainder being associated with the lignin portion. Methoxyl groups in the hemicellulose fractions and residues accounted for only about 70% of those present in the holocelluloses. No glycosidic methoxyls were found and the amt. of ester methoxyl was too small to account for losses by saponi-fication. The conclusion was reached that some of the ether methoxyls were cleaved during the alkali extraction of the holocelluloses. Methoxyl values in the alpha-cellulose residues as contained by the Zeisel method were considerably greater than those of the trimethylamine procedure. Uronic acid groups of the extractive-free straw were almost quantitatively accounted for in the various fractions. The molar ratio [image] which was less than unit in the [image] celluloses, increased to greater than unity in the hemicel-luloses A and B of both straws.

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