Christopher J. Biermann

Hydrolysis and other Cleavages of Glycosidic Linkages in Polysaccharides

Publisher Summary This chapter discusses the cleavage of glycosidic linkages useful for the analysis of oligo- and polysaccharides. The cleavage of glycosidic linkages of larger oligo- and polysaccharides is necessary to determine the monosaccharides that compose the larger carbohydrate. Hydrolysis—that is, the cleavage of a bond by the addition of the elements of a water molecule, is the most common method for the cleavage of glycosidic linkages. Hydrolysis is carried out in aqueous solutions with an acid catalyst, although some special-purpose hydrolyses, such as the liberation of carbohydrate chains from glycoconjugates, require alkaline catalysts. Common acid catalysts are hydrochloric, sulfuric, and trifluoroacetic acids. Glycosidic linkages may also be cleaved in other solvents such as methanol. In this case, water is rigorously excluded so that the elements of a molecule of methanol are added across the glycosidic linkage to afford the methyl glycosides. Methanolysis is usually catalyzed by the addition of dry hydrogen chloride to methanol. Other solvents, such as acetic anhydride-acetic acid (acetolysis) and formic acid (formolysis), are occasionally used for special purposes.

Grafting of partially hydrolysed poly(methyl methacrylate) onto mesylated cellulose acetate

Abstract A new synthetic route to cellulose graft polymers by nucleophilic displacement of mesylate groups from mesyl cellulose acetate (MCA) by the polystyrylcarboxylate anion has been recently reported by us. This approach to cellulosic graft polymers overcomes the drawbacks of the radical polymerization methods and allows for precise control of parameters such as the molecular weight and molecular weight distribution of the grafted side chains, higher degree of substitution on the cellulose backbone, the number and nature of grafted side chains and overall better control and reproducibility of the grafting process. In this report, partially hydrolysed poly(methyl methacrylate) was successfully grafted on to mesylated cellulose acetate in excellent yields by nucleophilic displacement of mesylate groups in less than 60 min at 75°C.

Grafting of poly(ethylenimine) onto mesylated cellulose acetate, poly(methyl methacrylate) and poly(vinyl chloride)

Work on the formation of graft copolymers of cellulose derivatives has been continued by grafting poly(ethylenimine) (PEI) onto mesylated cellulose acetate (MCA) by second order nucleophilic displacement (SN2) of mesylate groups by amine groups. Three solutions each containing 5% MCA and 2·5, 5 and 10% PEI, respectively, in dimethylformamide (DMF) were reacted at 80°C. The first solution did not form a gel, while the others formed gels (since cross-linking occurs) in 3 h and 1·5 h, respectively. This indicates aminolysis of acetate groups was taking place preferentially to the SN2 reaction. Reaction of PEI with poly(methyl methacrylate) (PMMA) led to gelation, indicating that aminolysis of ester groups was occurring even with the ‘hindered’ esters of PMMA. The nucleophilic reaction leading to grafting was demonstrated by reaction of PEI with poly(vinyl chloride) (PVC), which also led to gelation. These grafting reactions could be used to produce cross-linked resins with high ion-exchange capacity.

The characterization of charcoal and high-density carbon pellets produced from Douglas-fir bark

High-density carbon pellets (HDCP) produced from Douglas-fir bark could provide an alternate source of carbon for industry. The production of HDCP in vertical retorts is discussed. Scanning electron microscopy (SEM), atomic absorption spectroscopy (AAS), carbon elemental analysis, and other analytical methods were used to characterize HDCP. HDCP produced from Douglas-fir bark in this work have 90% fixed carbon, an average density of 1.3 g/mL, and 1.18% average ash content with negligible metal impurities. These pellets should be particularly suited for use in the production of adsorbents, high-grade carbons, reductants, carbon black, carbon electrodes, and activated carbons.

The Utilization of Douglas-Fir Bark for the Production of Oxalic Acid and High Density Carbon Pellets

The production of oxalic acid by the catalytic oxidation of Douglas-fir (Psedotsuga menfiesii (Mirb) Franco) bark and subsequent pyrolysis of the residue to produce high density carbon pellets is discussed. Kinetic rate data are presented for oxalic acid production from Douglasfir bark. A maximum yield of 38 wt% oxalic acid has been obtained in 8 h at 80°C with 62.5 vol% HNO3 and 0.5 mg V2O5/g of bark. Additional oxalic acid can be produced by the conversion of pyrolytic oils and tars (obtained during carbonization of the residue) to increase the total yield to 45 wt%. An economic analysis based on the current cost of oxalic acid indicates the viability of the proposed process.