Chemical comparison between three Amazonian woods and north American hardwoods / Marcia Moura Bananeira.

Tese (M.S.) - Colorado State University, 1986

A complete chemical analysis of three commercial tropical Amazonian species (Plastimicium ulei, Maquira guianensis and Virola surinamensis) was determined by using generally recommended procedures. The following quantitative determinations were made: extractives, 1% NaOH solubility, ash, lignin (acid insoluble and acid soluble), methoxyl (in wood and in lignin), acetyl, uronic anhydride, pentosans, holocellulose and alpha-cellulose. For the isolation of hemicelluloses; wood was delignified by the chlorite method and extracted with dimethyl sulfoxide which removed the acetylated 4-0-methylglucurono xylan. The residue was then extracted with aqueous sodium hydroxide containing borate yielding glucomannan and alkaline xylan. The remaining residue was modified alpha-cellulose. To characterize the xylan, it was necessary to determine the amount of constituents; methoxyl, acetyl and uronic acid. In the investigation of polysaccharides, the type and quantity of sugar units was determined. The material was hydrolyzed, reduced with sodium borohydride to form alditols, which in turn were acetylated with acetic anhydride. The acetates were dissolved in methylene chloride and isolated by gas-liquid chromotography. The ratios of uronic: O-acetyl-4-methoxyglucuronoxylan and acetyl: O-acetyl-4-methoxyglucuronoxylan were determined to indicate the degree of substitution of the xylan with regard to uronic acid and acetyl groups, respectively. The total of 4-0-metrhoxyglucuronoxylan in wood was also determined. From the glucomannan preparation, the ratio of glucose to mannose was determined, as well as the total glucomannan content for each species. The analytical results obtained for the three Amazonian woods were compared with those in the literature for North American hardwoods. Based on the comparison, it can be said that, these three Amazonian woods are higher in cellulose, higher in lignin, lower in actyl, lower in pentosans and lower in mannan than are the North American hardwoods. .