Dioxane Lignin Research Articles

A study of dioxane lignin from bolls of the cotton plant of variety AN Bayaut-2 II

The dioxane lignin was isolated from ripe bolls of a medium-fiber cotton plant of the variety AN Bayaut-2. Its developed empirical formula was derived, its UV, IR, and PMR spectra were recorded, and its molecular weight was determined. It was shown that the boll lignin is more condensed than the stem lignin. It differs from the stem lignin by a lower content of methoxy groups and a higher content of hydroxy and carbonyl groups.

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.

Cleavage of the natural lignin and the dioxane lignin of kenaf by thioacetic acid

The dioxane lignin and the natural lignin of kenaf undergo 37.62% and 94.6% cleavage, respectively. The combined monomeric degradation products have been studied by the GLC method. The presence of substances relating to three types of structural units has been established: p-coumaryl, gualacyl, and syringyl. It has been shown by chromatography on Sephadex LH-20 (with ethanol-water (9:1) as solvent and eluent) that the phenolic products of degradation extracted by ethyl acetate at pH 2 consist of five fractions: oligomers, tetramers, trimers, dimers, and monomers.

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.

Lignin of the fine-fibered cotton plant of variety S-6030 affected by fusarial wilt. II

A comparative study of the products of cleavage by sodium in liquid ammonia of the dioxane lignins (DLAs) from healthy and fusarial-wilt-affected stems of the fine-fibered cotton plant of variety S-6030 and a study of the PMR spectra of both lignins has shown that the DLA from the healthy stems is more highly condensed than the DLA of the stems affected by wilt. The main structures of DNA wilt are of the guaiacyl type. In the DLA from the affected stems, the amount of p-coumaryl structures had increased, which confirms the demethylating action of fusarial wilt on cotton-plant lignin.

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.

Silicon-29 NMR Spectroscopy in Lignin Chemistry - Application to Trimethylsilylated Spruce Dioxane Lignin and Related Model Compounds

Silicon-29 NMR Spectroscopy in Lignin Chemistry - Application to Trimethylsilylated Spruce Dioxane Lignin and Related Model Compounds

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.

Temperature dependence of the tensile properties of lignin/paper composites

The mechanical properties of dioxane lignin (DL)/paper and kraft lignin (KL)/paper composites were investigated as functions of temperature and strain rate. The tensile properties of the lignin/paper composites were governed by the viscoelastic properties of lignins used as a matrix. In the temperature dependence of the tensile properties, the strength of DL/paper composite decreased at 70° and 130°C at which the elongation had maxima. This behaviour was caused by the viscoelastic properties of DL having two relaxations in the primary dispersion region at 120° and 160°C. In the case of KL/paper composite, a drastic decrease in the strength and maximum of elongation were observed at the glass transition of KL (140°C). The strain rate dependence of the strength of DL/paper composite showed behaviour typical of viscoelastic materials. The strength increased with increase of the strain rate and then decreased after reaching a maximum, which showed a transition from a brittle to a ductile type of fracture.

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.

A study of the lignin of the sea island cotton plant of variety S-6030

The dioxane lignin has been isolated by Pepper's method with a yield of 9.5% on the Komarov lignin from the ripe stems of the sea island cotton plant of variety S-6030. The developed emperical formula has been calculated, the IR and UV spectra have been taken, and the molecular-mass distribution has been studied. The dioxane lignin is polydisperse. Mw=10,100, Mn=5350.

Dioxane lignin of the stems of the cotton plant of variety Tashkent 1 wholly affected by wilt

Dioxane lignin of the stems of the cotton plant of variety Tashkent 1 wholly affected by wilt

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 Bjorkman 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.

A study of rice lignin

For a comparison study of the dioxane lignins of rice husks and of ripe rice stems, the DLA of ripe rice stems has been isolated by a modification of Pepper's method with a yield of 5.25% on the plant and 25% on the Komarov lignin. The amounts of the main functional groups in the two lignins are similar. The semiempirical formulas have been calculated on the basis of elementary and functional analysis. IR, UV, and PMR spectra of the DLA have been taken. It has been established by gel chromatography on Sephadex G-75 that the DLA of ripe rice stems is polydisperse and the molecular weight has a number-average value of 3900, a weight-average value of 5300, and a mean value of 9800.

A study of the lignin of the cotton plant of the subspeciesmexicanium

p-Hydroxybenzoic, vanillic, ferulic, and syringic acids, and also p-hydroxybenzalde-hyde and vanillin, have been found in an ethanol-benzene extract of the stems of cotton plants of the subspeciesmexicanium. The dioxane lignin (DLA) has been isolated by Pepper's method, the semiempirical formula of its phenylpropane structural unit and its molecular-mass distribution have been established, and its UV, IR, and PMR spectra have been recorded. The DLA has a comparatively low molecular mass and a lower degree of polydispersity than the dioxane lignin of the cotton plant of variety Tashkent-1, while the amounts of functional groups in them coincide, with the exception of a lower amount of carboxy groups in the DLA.

Structure of the lignin of cotton plants of the subspeciesmexicanium

The nitrobenzene oxidation and cleavage with metallic sodium and liquid ammonia and with thioacetic acid (TAA) of the natural lignin of cotton plants of the subspeciesmexicanium and of the dioxane lignin (DLA) isolated from it have been performed. A comparison of the yields of the products and their compositions has shown that the most complete and reliable results are given by cleavage with TAA, under which a considerable part of the lignin suffers destruction. The high content of monomeric and dimeric fractions in the products of TAA cleavage shows a low degree of condensation of the lignin of cotton plants of the subspeciesmexicanium.

Fractional composition of kenaf dioxane lignin

The fractionation of kenaf dioxane lignin according to molecular weights has been carried out. The six fractions obtained differ by their molecular masses and chemical compositions. Semiempirical formulas of all the fractions have been deduced. The relative optical densities have been calculated on the basis of the IR spectra of the fractions.

Poplar Lignin Decomposition by Gram-Negative Aerobic Bacteria

Eleven gram-negative aerobic bacteria (Pseudomonadaceae and Neisseriaceae) out of 122 soil isolates were selected for their ability to assimilate poplar dioxane lignin without a cosubstrate. Dioxane lignin and milled wood lignin degradation rates ranged between 20 and 40% of initial content after 7 days in mineral medium, as determined by a loss of absorbance at 280 nm; 10 strains could degrade in situ lignin, as evidenced by the decrease of the acetyl bromide lignin content of microtome wood sections. No degradation of wood polysaccharides was detected. Lignin biodegradation by Pseudomonas 106 was confirmed by CO(2) release from labeled poplar wood, although in lower yields compared with results obtained through chemical analysis based on acetyl bromide residual lignin determination.

The Influence of Anthrahydroquinone and Other Additives on the Condensation Reactions of Vanillyl Alcohol

Abstract Vanillyl alcohol, a simple lignin model, has been heated with alkali under a variety of conditions and in the presence of several additives. The level of condensed products, principally dimers and trimers, has been determined in each case. Some additives, such as sulfide and anthraquinone, showed few differences from the control. Other additives, such as anthrahydroquinone, dithionite and 3,5-dinitrobenzoic acid, greatly depressed the levels of condensation products. The detection of a minor product, a head-to-head dimer, suggests some radical intermediates are present under these reaction conditions. The degree of condensation and ratio of products was quite temperature dependent. The influence of selected additives on the condensation reactions of a dioxane lignin has also been studied.

Aminomethylation of dioxane lignins of healthy and wilt-diseased cotton plants of the variety Tashkent-1

The products of the aminomethylation of dioxane lignins of healthy and wilt-diseased plants of variety Tashkent-1 according to the vegetation periods (ADLKhT-1-VII) have been studied. It has been established that the dioxane lignins of the wilt-diseased cotton-plant stems are less condensed.