Kyosti V. Sarkanen

Kinetics of Organosolv Delignification in Batch- and Flow-Through Reactors

Etude de la cinetique de delignification du bois de Populus trichocarpa dans une solution aqueuse de methanol

Synthesis and kinetics of acid-catalyzed hydrolysis of some α-aryl ether lignin model compounds

Aseries of α-aryl ether lignin model compounds were synthesized and their rates of acid-catalyzed hydrolysis were determined in ethanol-water media.The rates were all first-order with respect to both catalystand Substrate concentrations. With varying Substitution patterns of the benzyl moiety, the hydrolysis rates decreased in the Order: 4-methoxy s 3,4-dimethoxy-»3,45 trimethoxybenzyl. On the other hand, varying structures of the aryl ether moiety caused the following rate effects: 2,6-dimethoxy-»2-methoxy-4methyl->2-methoxyphenyl. Addition of an aryloxymethyl substituent to the benzylic carbon reduced the hydrolysis rate to approximately forty percent of its original value.The activation energies for the hydrolysis of individual model compounds varied in the r nge from 79 to 118 kJ/mol.

The Isolation and Characterization of the Lignins of Jute (Corchorus capsularis)

Milled wood lignin (MWL) and enzymatically liberated lignin (ELL) were isolated from jute fiber and jute stick tissues. Alkali lignin (AL) was isolated from jute fiber. The lignins were characterized on the basis of FT1R, UV, H and C NMR spectroscopy. The molar ratio of syringaldehydc to vanillin (S/V) from alkaline nitrobenzene oxidative cleavage was found to be 2.0 for fiber and 1.4 for stick lignins, respectively. The Q formulas were calculated for fiber MWL, stick MWL, fiber ELL, stick ELL and fiber AL as C9H8.I803.23(OCH3)U3, CyH^CWOCHa),^, C9H^3(}O3,3K(OCH3)L44· ^Ητ99Ο3Λ3(Ο€Η3)}^ and QH736O2.43(OCH3)if2i, based on their mcthoxyl and elemental analyses. Estimating the xylan content of the isolated lignins to be 5%, the corresponding xylan free formulations become C<jH7^)3O3M (OCH3)u8, QH^O^OCH^.^, QH8.o403.21(OCH3)J)50, C9H7.74O2.96(OCH3)1.41 respectively. From cry thro and threo ratios, it is evident that the β—Ο—4 structures are mainly of the erythro-synngy\ ether type. In general, the characteristics of jute lignins are similar to hardwood.

Acidic permanganate oxidations of lignin and model compounds: Comparison with ozonolysis

Acid permanganate oxidation degrades completely the aromatic moieties of lignins and lignin model compounds while a part of the side-chain structures can be recovered intact in the form of carboxylic acids. Thus, threonic acid (6.9%) is obtained from threo-veratrylglycerol, erythronic acid (7.8%) from erythro-veratrylglycerol φ-(2-methoxyphenyl) ether and glycolic acid (∼13%) from vanillyl alcohol. Erythronic and threonic acids, in a molar ratio of 0.6:1, were also identified as permanganate oxidation products of black spruce native lignin. Minor oxidation products from lignin and lignin model compounds included glyceric, oxalic, glycolic, tartronic, erythraric, threaric, 2,4-dihydroxybutanoic, succinic and malic acids

Formation of C6 C2 -Enol Ethers in the Acid-Catalyzed Hydrolysis of Erythro-Veratrylglycerol-β-(2-Methoxyphenyl) Ether

Abstract Acid-catalyzed hydrolysis of erythro-veratrylglycerol-β-(2-methoxyphenyl) ether in mixed aqueous-organic media yields, in addition to Hibberts ketones formed via readily hydrolyzable C6 C3 -enol ether intermediates, the cis-and trans-isomers of a C6 C2 -enol ether. The formation of these C6 C2 isomers involves the elimination of the γ-carbinol group as formaldehyde. Both C6 C2 -enol ether isomers are unexpectedly resistant towards hydrolysis. In aqueous dioxane and ethanol systems, the competing formation of the C6 C2 -enol ethers is increased with increasing concentration of the organic solvent and with increasing reaction temperature.

Marine plant polymers : Part III. A kinetic analysis of the alkaline degradation of polysaccharides with specific reference to (1→3)-β-D-glucans

Abstract A general kinetic expression is presented for the rate of alkaline degradation of linear polysaccharides in terms of mono- and di-anionic species formed from the reducing end-groups. Specific rate constants have been determined for the end-wise depolymerization of the (1→3)-β- D -glucans, laminaran, laricinan, and pachyman, and compared with similar data for amylose degradation. The rate constants of degradative chain-propagation via the mono- and di-anion intermediates have been shown to be essentially equal. The effect of the type and concentration of base on the mechanism of end-wise degradation is described for both (1→3)-linked and (1→4)-linked polysaccharides. Inhibition of alkaline degradation is discussed in terms of chain branching and blockage of reducing end-groups.

Donnan Equilibria in Wood-Alkali Interactions. Part I. Quantitative Determination of Carboxyl-, Carboxyl Ester and Phenolic Hydroxyl Groups

Abstract The functional groups in wood that may become ionized by the action of sodium hydroxide consist of carboxyl, phenolic hydroxyl and carbohydrate hydroxyl groups. The extent of ionization is dependent on the pH of the solution and causes the establishment of a Donnan equilibrium between the outer solution phase and that associated with the solid phase. Analytical techniques were developed to determine the carboxyl and phenolic hydroxyl contents of extractive-free mildly saponified hemlock and cottonwood meals using equilibration in the pH range of 12 to 12.5. The determined carboxyl contents, 0.158 and 0.127 meq/g OD wood, respectively, were confirmed by conductometric titrations of wood meal samples methylated with diazomethane prior to saponification with NaOH. Further confirmation was obtained from conductometric titrations of saponified and HCl-washed samples with NaHCO3. The last-mentioned method was also applied to unsaponified hemlock and cottonwood samples to obtain their free carboxyl cont...

The use of alkaline degradation for structural characterization of branched-chain polysaccharides

Abstract Classical methods of polysaccharide characterization are often inadequate for the evaluation of the number and nature of sugar residues associated with side-branches. This investigation demonstrates that controlled, alkaline degradation may be used to eliminate the backbone of the molecule and to convert branches linked through position 6 of the backbone into individual entities containing saccharinic acid end-groups. Application of alkaline degradation to an arabinogalactan revealed that arabinose residues are present not only in the branches but also in the backbone of the molecule. Furthermore it has been shown that, in addition to single-unit and two-unit branches, a few branches contain as many as ten residues.

Formation and Reaction of Coniferyl Alcohol During Alkaline Pulping

Abstract The formation and subsequent disappearance of coniferyl alcohol during kraft and soda-AQ (anthraquinone) pulping of western hemlock wood meal have been studied under isothermal condition. At 140°C, the amount of coniferyl alcohol generated increases to a sharp maximum (0.4% of total lignin in kraft and 1.9% in soda-AQ pulping) and then declines rapidly to low values. It was found that the disappearance of coniferyl alcohol was mainly due to condensation with other components of dissolved lignin. Nearly identical activation energies, 125 kJ mole−1 for kraft and 128 kJ mole−1 for soda-AQ pulping, were derived from the initial rates of coniferyl alcohol formation, conforming closely with the value 121 kJ mole−1 for the cleavage of phenolic β-ether model compounds in the kraft process.

Oxidative dimerizations of (E)- and (Z)-isoeugenol (2-methoxy-4-pro-penylphenol) and (E)- and (Z)-2,6-dimethoxy-4-propenylphenol

Reaction of (E)-isoeugenol (3) with 1 equiv. of hydrogen peroxide catalysed by peroxidase gives a mixture of dehydrodi-isoeugenol {4-[2,3-dihydro-7-methoxy-3-methyl-5-(E)-propenylbenzofuran-2-yl]-2-methoxyphenol}(7a)(65%). threo- and erythro-1 -(4-hydroxy-3-methoxyphenyl)-2-[2-methoxy-4-(E)-propenylphenoxy]propan-1-ol (9a)(17%) and (10a)(5%). and isomers of 2,5-bis-(4-hydroxy-3-methoxyphenyl)-3,4-dimethyltetrahydro-furan (13a)(4%) and (14a)(9%) which result from β–5. β–O, and β–β coupling, respectively. Oxidation of (Z)-isoeugenol (4) under identical conditions yields products differing only in the propenyl side-chain configurations of compounds (7), (9), and (10): viz. (7b)(22%), (9b)(40%), (10b)(13%), (13a)(8%), and (14a)(17%). The tetrahydrofuran dimethyl ethers (13b) and (14b) were identified as the (±)-forms of the lignans galbelgin and veraguensin, respectively. Oxidation of (E)-2,6-dimethoxy-4-propenylphenol (5) with 1 equiv. of hydrogen peroxide-peroxidase or potassium ferricyanide affords a 1 : 2 mixture of isomers of 2,5-bis-(4-hydroxy-3,5-di-methoxyphenyl)-3,4-dimethyltetrahydrofuran (13c) and (14c). In identical oxidative treatments, the (Z)-phenol (6) gives isomers (13c), (14c), (15c), and (16c) in the ratio 1:2:2:1. The tetrahydrofuran configurations were assigned by reductive degradation experiments involving ring scission and by n.m.r. spectral comparisons with analogous lignans. The β–β coupling of phenols (3)–(5) is remarkably stereospecific and produces exclusively threo-compounds. whereas the (Z)-phenol (6) gives threo- and erythro-coupling products in equal amounts, A mechanism is proposed for this coupling which involves the intermediacy of a dimeric ‘tail-to-tail’ charge-transfer complex, formed by association of phenoxyl radicals. The feasibility of the alternative ‘head-to-tail’ complexes is also discussed. The differences in the probabilities of coupling modes in the oxidations of (E)- and (Z)-isoeugenol is considered to be due to the characteristics of these intermediate complexes rather than to the differences in free-electron densities.