The Chemistry of Wood II—Water-Soluble Polysaccharide of Western Larch Wood¹

Abstract

3) reported the presence of a water-soluble polysaccharide in western l a r c h (Larix occidentalis, Nuttall).This interesting substance, on hydrolysis, gave extraord i n a r i l y high yields of galactose, and Schorger and Smith ventured the opinion that this was the only sugar formed.The water-soluble s u bstance, which was termed "Egalactan" by its discoverers, when distilled with 12 per cent I The water-soluble +galactan of western larch, described by Schorger and Smith, yields 11.95 per cent arabinose and 84.6 per cent galactose on complete hydrolysis and appears to be an arabogalactan. Over 70 per cent of the galactose present, as indicated by analysis, could actually be separated in crystalline form. The arabinose was identified through its benzylphenylhydrazone and the diphenylhydrazone.Van der Haar's modification of Tollen's mucic acid method gives a fair approximation of the galactose content in e-galactan hydrolysis mixtures. A modification of the Neuberg-Wohlgemuth method for arabinose furnishes a convenient proximate means of estimating this sugar. The excellent thiobarbituric acid method for furfural devised by Dox and Plaisance is admirably suited to the accurate determination of of galactose.h y d r o c h l o r i c acid, yielded about 6.2 per cent furfural, while pure galactose under similar conditions gave rise to only 0.55 per cent of an aldehyde calculated as furfural. In explanation of this phenomenon, Schorger and Smith make the following comment: "It is believed that the formation of furfural is due to the peculiar structure of the galactan molecule, and not to the presence of a pentosan residue."I n a preliminary investigation on €-galactan, the present writers were able, not only to check Schorger and Smith's furfural yields in the case of the original polysaccharide, but to obtain practically the same furfural yields after the complete hydrolysis of the galactan. Theoretically such a hydrolysate, if it contained galactose as the sole sugar, should yield only negligible amounts of aldehyde when distilled with 12 per cent hydrochloric acid, This intriguing discrepancy caused the writers to repeat and to extend Schorger and Smith's work on e-galactan. The results virtually substantiated those of the previous investigators, with one important exception. Arabinose was definitely shown to be one of the products of the €-galactan hydrolysis and the percentage of arabinose (determined gravimetrically as the diphenylhydrazone) accounted quantitatively for the furfural yield obtained from the hydrolyzed galactan by two different methods. A series of careful determinations of galactose and arabinose indicated the presence of 84 to 85 per cent anhydrogalactose arabinose in the presence 1 Received January 20, 1930. Presented under the subtitle by L. E. Wise before the Division of Cellulose Chemistry at the 78th Meeting of the American Chemical Society, Minneapolis, Minn., September 9 to 13, 1929. The first article in this series, by Harlow and Wise, was published in IND. ENG. CHSM., 40, 720 (1928). an...

The Chemistry of Reaction Wood. Part II. The Polysaccharides ofEucalyptus goniocalyxandPinus radiata

“…Galactose was determin.ed by the method of Wise and Peterson (1930) except that precipitation was carried out at 20° C. Duplicates of three galactose Solutions of known concentration were analysed with each batch of unknowns. -This constituent was determined by nitric acid oxidation of the hydrolysates of wood, or modified wood.…”

Quantitative Determination of Hemicellulose Constituents by Fermentation

“…838) would selectively ferment D-xylose in the presence of L-arabinose and certain other sugars. However, in a study of the fermentation of wood-sugar stillage, Kurth and Cheldelin (8) claim that H. suaveolens (NRRL No. 838) and Candida lipolytica (NRRL No.…”

Quantitative Determination of 5-Methyl Furfural

“…The methods selected for study were the phloroglucinol or A. O. A. C. method (7), the thiobarbituric acid method (3,10,17,19), the 2, 4-dinitrophenylhydrazine method (8,16), the volumetric bromidebromate titration method [ß, 4, 10-13, IS), and the volumetric bromide-bromate titration at 0°C. (7).…”