PMR spectra of the lignins ofCystoseira barbata at different ages

The PMR spectra of the dioxane lignins from the brown algaCystoseira have been studied. It has been established that the lignins isolated from specimens ofCystoseira of different ages have different degrees of substitution of the C₃ side chain and differ in their degree of condensation. The most highly condensed is the dioxane lignin of young specimens ofCystoseira (age up to one year) and the least condensed the Björkman lignin ofCystoseira aged more than three years. All the PMR spectra of preparations of the lignin of the alga under investigation contain the signals of protons present in coumaran structures, their amount being the greatest in the lignins of the youngest samples and decreasing with increasing age of the alga.Odessa Institute of Structural Engineering. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 91–94, January–February, 1983.     

Macromolecular properties and topological structure of spruce dioxane lignin

Samples of spruce dioxane lignin were isolated by means of six-stage extraction from spruce sawdust, their macromolecular characteristics were determined, and the hydrodynamic properties of the fractions were studied. The conformational properties and the topological structure of dioxane lignin were characterized. The heterogeneity of spruce dioxane lignin isolated in the successive steps of organosolv delignification was established, a property that is confirmed by the variability of the Tsvetkov-Klenin hydrodynamic invariant and a departure from linearity of the logarithmic dependence of the diffusion coefficient on the molecular mass. It was assumed that dioxane lignin macromolecules exist as branched polymers at M _w< 2 × 10⁴ and a network structure is formed at M _w > 2 × 10⁴.     

Investigation of the dihydroxylignin ofAlthaea rhyticarpa

Summary 1. The developed semiempirical formula for the dioxane lignin from the stems ofAlthaea rhyticarpa has been found from the results of elementary and functional analyses.2. It has been shown that the lignin consists of high- and low-molecular-weight fractions.3. It has been shown by the nitrobenzene oxidation method that p-coumaryl, guaiacyl, and syringyl structural units are present in the lignin.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 242–246, March–April, 1976.     

An investigation of the dioxane lignin of cotton bolls

Summary 1. Dioxane lignin has been isolated from mature stems of the cotton plantGossypium hirsutum by mild acidolysis in an atmosphere of nitrogen.2. Its expanded semiempirical formula has been established by elementary and functional analyses.3. The molecular-weight distribution of the dioxane lignin has shown that it consists of high-molecular-weight and low-molecular-weight fractions.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 645–648, September–October, 1974.     

Study of the lignin of cotton plants of the variety AN Bayaut-2. I

The dioxane lignin has been isolated from ripe stems of a cotton plant of the variety AN Bayaut-2. Its developed empirical formula has been derived, its UV, IR, and PMR spectra have been recorded, and its molecular weight has been determined. It has been shown that the dioxane lignins of the stems of cotton plants of different varieties differ in chemical structure.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 101–104, January–February, 1986.     

Quantitative1H and13C NMR spectroscopy of lignins isolated from aspen wood by various methods

A comparative analysis has been made of the chemical structures of aspen milled wood lignin, aspen dioxane lignin, and lignin from the explosive autohydrolysis of aspen wood.Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 878–886, November–December, 1995. Original article submitted November 22, 1994.     

Formation of peroxide compounds on the oxidation of lignin by oxygen in an organic solvent

The results are given of a determination of the steady-state concentrations of peroxide compounds on the oxidation of lignin by oxygen in dioxane. An iodometric method of determining peroxides was used, with spectrophotometric control of the amount of iodine formed. It was established that the achievable steady-state concentration of peroxide compounds on the oxidation of lignin is 0.28–0.44 wt. % of O_act (oxygen pressure 1 atm, temperature 50–80°C). With a rise in the temperature, the steady-state concentration of peroxide compounds decreased. The addition of water (30 vol. %) to the organic solvent led to an increase in the rate of accumulation of peroxide compounds. It has been shown that the presence of alkaline and acidic catalysts exerts no appreciable influence on the achievable steady-state concentration and the rate of accumulation of peroxide compounds during the oxidation of lignin.Bratsk Industrial Institute. All-Union Scientific Production Combine of the Pulp and Paper Industry, Leningrad. Translated from Khimiya Prirodnykh Soedinenii, Nos. 3,4, pp. 413–417, May–August, 1992.     

Dioxane lignin from shoots of the cotton plant of variety 108-F. I

The dioxane lignin has been isolated by Pepper's method from two-week shoots of the cotton plant of variety 108-F and has been separated into two fractions — insoluble and soluble in ether — DLA-A and DLA-B, respectively. It has been shown that in the early stage of development of the cotton plant a low-molecular-weight lignin with a low degree of methoxylation and distinctly different from the lignin from ripe stems of the same cotton plant is synthesized.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 96–98, January–February, 1984.     

The lignin of the sea island cotton plant of variety S-6030 affected by fusarial wilt. I

A comparative study of the dioxane lignins isolated from healthy and wilt-affected cotton plant stems has shown thatFusarium fungi demethylate lignin and make it more oxidized than the lignin from healthy stems.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 825–827, November–December, 1985.     

Schematic structure of a fragment of the cottonplant lignin macromolecule

A schematic structure has been proposed for an average fragment of the macromolecule of cottonplant dioxane lignin on the basis of the results of a chemical study and quantitative¹H and¹³C NMR spectroscopy.Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 234–236, March–April, 1996. Original article submitted June 27, 1994.     

Phosphorylation of lignins I. Phosphorylation of piperidinomethylated dioxane lignin from cottonseed husks

The phosphorylation of piperidinomethylated dioxane lignin has been studied. It has been shown that the reaction takes place with the formation of quaternary ammonium phosphates, while the transesterification of dimethyl phosphite with an aliphatic hydroxy group of the lignin is also possible.Institute of Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 275–277, March–April, 1993.     

Cleavage of dioxane lignin of the cotton plant with thioacetic acid

Summary 1. It has been established that the dioxane lignin of mature cotton-plant stems is cleaved by thioacetic acid. About 3/4 of the bonds in the lignin are alkyl-aryl ether bonds and only 1/4 are C-C bonds.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 505–507, July–August, 1978.     

An investigation of the lignins of healthy and wilt-affected cotton plants of variety Tashkent-1 according to the vegetation periods

Summary 1. The dioxane lignins of healthy and wilt-affected cotton plants of variety Tashkent-1 have been isolated and have been studied comparatively in relation to the vegetation period. On the basis of elementary and functional analysis, semiempirical formulas of the dioxane lignins isolated (DLCT-I to -VII) have been determined and it has been established that the dioxane lignins isolated from the wilt-affected plants contain more OCH₃ groups per phenyl-propane structural unit than the lignins of healthy plants.2. The molecular-weight distributions of the dioxane lignins have been studied and it has been shown that all the dioxane lignins isolated are polydisperse, those of the affected plants to a greater degree.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 260–264, March–April, 1978.     

Influence of additions of anthraquinone on the alkaline hydrolysis of cotton-plant lignin

The action of catalytic amounts of anthraquinone on the alkaline hydrolysis of the stems and dioxane lignin of the cotton plant of the ssp.mexicanium has been investigated. It has been established that this leads to a substantial increase in the yield of low-molecular-weight hydrolysis products. Analysis of the monomeric fractions of the hydrolysis products by the GLC method has shown the presence in them of large amounts of substances with a p-coumaryl structure. This, and also the low level of syringyl derivatives, may be caused by the demethoxylation of the lignin under the conditions described.Institute of the Chemistry of Plant Substances, Academy of Sciences of the USSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 391–395, May–June, 1985.     

Change in the structural elements of cotton-plant lignins in the various vegetation periods

Summary 1. The dioxane lignins of the cottonplant of various vegetation periods have been studied, and it has been shown that the lignin changes in the course of the development of the plant: the amount of methoxy groups increases and the amount of phenolic hydroxy groups decreases.2. Gel chromatography of the lignins has shown that they are all polydisperse with a predominance of the high-molecular-weight fraction.3. The 3,4-diethoxybenzaldehyde detected in the products of the alkaline nitrobenzene oxidation of dioxane lignin of the early vegetation period after its ethylation with diethyl sulfate is a direct proof of the presence of catechol structural units in cotton-plant lignin.4. A quantitative determination of the catechol structures in the lignins of the cottonplant has shown that their amount decreases as the plant develops.5. By decomposing the lignins with sodium and liquid ammonia, the presence in them of guaiacyl, syringyl, and p-coumaryl structural units has been confirmed and it has been shown that the lignin becomes less condensed as the plant grows, which is apparently connected with an increase in the degree of its methoxylation.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 100–107, January–February, 1977.     

Anion dependence of crown ether selectivities for alkali picrates and sulfonates in dioxane and toluene. A synergistic effect

The binding constants,K _N, of sodium and potassium 8-anilinonaphthalene-1-sulfonate (ANS) and of sodium 5-dimethylamino-1-naphthalenesulfonate (DNS) to benzo-18-crown-6 bound to a 2% cross-linked polystyrene network (RN18C6) were measured spectrophotometrically in dioxane and the results compared with those obtained for picrate salts. The network RN18C6 was then used to measure in dioxane and toluene by a competition method the equilibrium constant,K, of the reaction A^–M⁺N+CrA^–M⁺Cr+N.A^–M⁺N denotes the ionic solute (ANS, DNS, methyl orange or picrate salt) bound to the network RN18C6 (N) and A^–M⁺Cr is the solute bound to a soluble ligand Cr, where Cr represents a series of 18-crown-6 and 15-crown-5 compounds. Combining theK _N andK values the formation constants,K _L, of the crown ether complexes of the respective salts were obtained in dioxane. The data show a reversal in the complexation strength of the 18-crown-6 compounds in dioxane when sodium picrate is replaced by sodium ANS. The results were rationalized in terms of a synergistic effect exerted by dioxane, with dioxane forming a 1:1 dioxanate with the crown ion pair complex. This effect is especially strong with ANS and with a rigid planar crown ether like dibenzo-18-crown-6. The binding constants,K _N, of NaANS and NaDNS to RN18C6 in dioxane are nearly three times larger than for sodium picrate, and the same holds for the potassium salts. Differences in anion interactions with the network appear to be a plausible cause for the anion dependence ofK _N.     

Hydrogenolysis of rice husk lignins

The hydrogenolysis of the protolignin, the hydrolysis lignin, and the dioxane lignin of rice husks in the presence of demethylated lignin as catalyst has been studied. The breakdown of the lignins into low-molecular-mass compounds took place with yields comparable with those obtained by hydrogenolysis using other catalysts.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 611–613, July–August, 1995. Original article submitted November 21, 1994.     

A study of the dioxane lignin of Ricinus communis

The dioxane lignin (DLA) isolated from a powder of the stems the castor-oil plant by a modification of Pepper's method has been investigated. The yield of DLA amounted to 19.85% on the Komarov lignin. On the basis of elementary and functional analysis, a developed semiempirical formula has been proposed for it from which it can be seen that the amounts of methoxy, aliphatic hydroxy, and carbonyl groups are high and that of phenolic hydroxyl low. UV, IR, and PMR spectra have been taken, and the molecular weight of the material has been determined.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 501–503, July–August, 1986.     

Cleavage by sodium in liquid ammonia of kenaf lignins and the biological activity of the cleavage products

The natural lignin of kenaf stems and fractions of the dioxane lignin of kenaf stems isolated previously were cleaved by sodium in liquid ammonia in order to study their structure. It was established that the kenaf lignins consist of three types of structural units: p-coumaryl, guaiacyl, and syringyl, with a predominance of the guaiacyl types. An antioxidation activity of the monomeric products of the degradation of the kenaf lignins has been found.Institute of the Chemistry of Plant Substances of the Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 738–742, September–October, 1987.     

Quantitative1H and13C NMR spectroscopies of cottonplant dioxane lignin

A comparative analysis has been made of the dioxane lignins of the stems, seedling shoots, and seed coats of the cotton plant. The ratio of p-hydroxyaromatic, guaiacyl, and syringyl units in the macromolecules of the lignins has been determined, and so have the amounts of functional groups and bonds. It has been established that the main difference between the dioxane lignins from seedling shoots and seed coats of the cotton plant, on the one hand, and the lignin from the woody stems, on the other hand is a lower content of syringyl and guaiacyl units in the former.Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 798–808, November–December, 1994.