Methoxyl content

The endo-action of the K. marxianus PG was demonstrated by a extremely rapid attack on plant tissue. This activity appears to be at least equivalent to that of several commercial preparations used for separating plant cells for protoplast preparation (RMC, unpublished data). Most of the endo-PGs produced by plant pathogens and saprophytes have so far been reported to possess macerating activity. PG secreted by K. marxianus CCT 3172 also had a strong activity in reducing the viscosity of cocoa pulp. Cocoa pulp generally contains 1 - 1.5% (w/w) of pectin consisting of 68% esterification and 11.6% methoxyl content [18]. 

The presence of three hydroxyl groups per glucose unit was shown by the preparation of a triacetate and a tribenzoate. Six or seven methyla-tions (using dimethyl sulfate and concentrated alkali) of dextran did not raise the methoxyl content above 41% (theoretical maximum 45.6%). Also, Purdie methylations (using methyl iodide and silver oxide) and methylation with thallium ethoxide and methyl iodide were ineffective in raising the methoxyl content of methylated dextran above 43.5%. The maximum theoretical methoxyl content was eventually attained by modified Muskat methylations. 6 Partially methylated dextran suspended in anisole solution was treated with sodium in liquid ammonia, and the sodium salt of methylated dextran thus formed was allowed to react with methyl iodide. The methoxyl content of the partially methylated dextran was raised by three such methylations from 42% to 45.5% and by five such methylations from 30% to 45.4%. 

Lignin may be defined as the incrusting material of the plant which is built up mainly, if not entirely, of phenylpropane building stones it carries the major part of the methoxyl content of the wood it is unhydrolyzable by acids readily oxidizable, soluble in hot alkali and bisulfite, and readily condenses with phenols and thio compounds (14). 

Table 9. Methoxyl Content of Bagasse Native Lignin and its Derivatives (111).

Repeated methylation of bagasse native lignin with dimethyl sulfate yielded a product with a 29-1 % methoxyl content. Four such methyl-ations did not change this value. However, the infrared spectrum of this derivative still revealed a small absorption band at 3400 cm1. Thus, it appeared that at least one hydroxyl group could not be methylated. Treatment of this methylated product with acetic anhydride and pyridine gave an acetate, which did not exhibit an absorption band at 3400 cm-1. Consequently, a tertiary hydroxyl group, which can be acetylated but not methylated, seems to be present in this lignin. 

Table 10. Methoxyl Content of Diazomethane Methylated Native and Enzymatically...

The native lignin from Paulownia tomentosa has been isolated and characterized in this laboratory. It has a methoxyl content of 16 6% and properties very similar to other native lignins (110). 

The various conflicting interpretations are attributed in part to the non-specific nature of the spectrum of lignin and more so to the fact that the. molecular weight of lignin is, as yet, unknown. Recently, Aulin-Erdtman (4) has successfully used the methoxyl content of various lignins instead of molecular weights in the determination of extinction coefficients. 

The data presented in a recent communication by Freudenberg et al. (32) show that the methoxyl content of the dehydrogenation polymers of coniferyl alcohol do not change with condensation time. However, their reference to p-hydroxycinnamyl alcohols seems to indicate their appreciation of the significance of a p-hydroxyphenylpropane unit in the mechanism of lignin formation. 

This review would be incomplete without mention of an important and rapidly developing new field in pectin chemistry and technology, namely that of the low-ester pectinic acids. In contrast to pectinic acids (pectins) of over 7% methoxyl content, pectinic acids containing 3-6% methoxyl are capable, in the presence of the required proportion of... 

The thallous derivative so formed was found to undergo metathesis with methyl iodide and to yield thallous iodide and methyl cellulose. Analyses of the latter product for methoxyl content after suitable purification yielded a measure of the accessible hydroxyl groups. The reactions were all conducted in non-aqueous systems. 

Evidence was presented that thallous ethylate did not penetrate or alter the crystalline parts of the fiber. Moreover, it was possible to conduct the thallation with different solvents for thallous ethylate. When this was done with normal ethers, the extent of methylation was observed to decrease as the molecular volume of the thallous ethylate solvent increased. These results suggested that accessibility is dependent upon the penetrating power of the ether solvent. Amorphous cellulose was, therefore, defined as the percentage of cellulose wetted by an ether of zero molecular volume and was estimated by determining methylation-molecular volume values for three or more straight-chain ethers, plotting the data and extrapolating to obtain methoxyl content for an ether of zero molecular volume. The amount of cellulose corre-... 

Methoxyl content of the different samples were determined using a modified Zeisel procedure (14). 

Lignin Characterization. Elemental analysis, TGA, methoxyl content, GPC, FTIR, and 13C NMR were used to characterize our prototype solvolytic lignin. 

Thermogravimetric weight loss for the OSL is similar to that of kraft lignin. Except for a slightly elevated methoxyl content, the NMR and degradation results in Table II are within the expected range for a hardwood lignin. 

Copolymerization reactions Copolymerization experiments with styrene and MMA employed molar fractions of 20, 40, 60, and 80% comonomers, which were reacted in ethanol 1,2-dichIorethane 60 40 (by volume) mixtures and benzoyl peroxide as catalyst. Polymerizations were carried out at 70°C. The reactions were quenched by the addition of methanol as non-solvent, and the copolymer was isolated by centrifugation. Copolymer analysis employed UV spectroscopy for copolymers with MMA, and methoxyl content determination according to a procedure by Hodges et al. (16) in the case of styrene copolymers. Reactivity ratios were determined in accordance with the method by Kelen-Tiidos (17) and that by Yezrielev-Brokhina-Roskin (YBR) (18). Experimental details and results are presented elsewhere (15). 

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