Presence Of Anthraquinone Research Articles

Studies on the alkaline degradation of cellulose. III. Alkaline treatment in presence of anthraquinone

Anthraquinone (AQ) reduces the rate of alkaline degradation of cotton and bagasse celluloses. This is due to the stabilization effect of AQ on the cellulose macromolecules. The D.P. values for the resulting oxycelluloses were in the order: alkali-AQ-treated cotton > alkali-AQ-treated bagasse > alkali-treated bagasse > alkali treated cotton. Thus, intracrystalline linkage with AQ is more efficient in chain stabilization in the alkaline degradation of cellulose than the intercrystalline linkages. This is because the latter is usually followed by intracrystalline degradation of decrystallized cellulose chains without AQ links. Furthermore, the bulky units of AQ penetrate within the cellulose chanis, separate them further apart and thus enhance decrystallization and accessibility. Also, many factors were found to affect the reactivity of the oxycelluloses obtained, namely, the chain length, availability of active groups and the extents of decrystallization and oxidation.

On the Mechanism of Methanol Oxidation Sensitized by Anthraquinone

The mechanism of photosensitized oxidation of methanol in acetonitrile was investigated in the presence of anthraquinone. Among the main stable products formaldehyde, formic acid, hydrogenperoxide and hydroxymethylhydroperoxide has been found. Their accumulation was measured in the range of 30–60°C. Specific experiments were carried out to prove the existence or negligibility of reactions proposed in the literature. The computer simulation based on literature data and on our results combined with estimation of certain rate coefficients as parameters resulted in good agreement with experimental product accumulation curves. The estimated value of monomolecular decomposition of hydroxymethylperoxyl radical (k325°C ≈ 3 s−1) is in favour of the lowest values that can be found in the literature. In the overall termination process the Russell-type termination step generally accepted in reactions between peroxyl radicals has decreasing importance with increasing temperature.

Photoaffinity labeling of the phylloquinone-binding polypeptides by 2-azidoanthraquinone in photosystem I particles

A photoaffinity label, 2-azido-9,10-anthraquinone, binds at the quinone-binding (Q φ) site with high affinity and can substitute for the secondary acceptor, phylloquinone, in photosystem I reaction center of spinach. Phylloquinone-depleted photosystem I particles reconstituted with azido-[ 3H]anthraquinone were illuminated with UV light and analyzed by sodium dodecylsulfate-polyacrylamide gel electrophoresis. The large core polypeptides ( psaA and/or psaB) were selectively labeled. The labeling was competitively inhibited in the presence of anthraquinone. These results indicate that the Q φ site is located on psaA or psaB polypeptides.

Identification by GC/MS of Acidic Compounds Produced During the Photosensitized Oxidation of Normal and Isoprenoid Alkanes in Seawater

Abstract Experiments carried out in vitro in the presence of anthraquinone allowed to simulate the photosensitized oxidation of linear and isoprenoid alkanes in the marine environment. The main acidic photoproducts formed after solar irradiation were identified by gas chromatography and gas chromatography/mass spectrometry and different mechanisms were proposed in order to explain their production. The detection of most of these photoproducts among the acidic compounds formed during the photodegradation of a petroleum fraction proved the suitability of anthraquinone as a model sensitizer for studies of the photochemical degradation of petroleum saturated hydrocarbons in water.

Mechanistic study of the photosensitized oxidation of cis-decalin and trans-decalin

cis-Decalin and trans-decalin were photooxidized in chloroform by sunlight in the presence of anthraquinone as sensitizer. The main photosensitized oxidation mechanisms, which act on all the carbon atoms of these molecules, were described and it appeared that steric factors strongly influenced their selectivity. An interesting photoisomerization mechanism of cis-1-decalone and trans-1-decalone was also proposed.

Cleavage of the natural lignin of cotton-plant stems with thioacetic acid in the presence of anthraquinone

The influence of additions of catalytic amounts of anthraquinone on the stages of hydrolysis in the cleavage of natural lignin by thioacetic acid has been investigated. The degree of delignification does not change under these conditions, but the yield of low-molecular-weight cleavage products increases, which indicates a profound degradation of the lignin macromolecule. The qualitative and quantitative compositions of the monomeric fractions of cleavage products do not undergo appreciable changes in the presence of anthraquinone.

Alkali Treatment of Xylotriose and Birch Xylan in the Presence of Anthraquinone.

Alkali Treatment of Xylotriose and Birch Xylan in the Presence of Anthraquinone.

Electron Transfer Reactions in Pulping Systems (II): Electrochemistry of Anthraquinone/Lignin Model Quinonemethides

Abstract Electron transfer reactions have been observed during the electrolyses of solutions containing anthraquinone and 8-aryl ether lignin model quinonemethides. In dry acetonitrile at a reduction potential of -0.9V (vs. Ag/AgCl) electrons are transferred from the electrode to anthraquinone (AQ) to form stable anthrahydroquinone radical anions (AHQ−). The lignin model quinonemethides are not reduced directly at the electrode at this potential but are reduced by AHQ− to give quinonemethide radical anions (QM−) and AQ. The QM− species rapidly fragment at their β-aryl ether bond to give phenolate ions and radicals; the latter further reduces to another phenolate ion. For example, the β-methyl lignin model QM 1 gives guaiacol and isoeugenol upon electrolysis at -0.9V in the presence of AQ. In wet acetonitrile, reduction of AQ at -0.9V leads to both anthrahydroquinone radical anion and dianion; the dianion is formed by direct electrolysis of the radical anion and by disproportlonation of the radical anion. ...

On the sensitized photo-oxidation of alkylbenzenes in seawater

Several homologous monoalkylated benzenes were photo-oxidized as surface films on and dissolved in pure water and purified natural seawater by solar and equivalent artificial UV irradiation in the presence of anthraquinone as photo-sensitizer. The main reaction products were the 1-phenylalkanones, the corresponding secondary alcohols, benzaldehyde and, when the side chain contained four or more carbon atoms, the products of what appears to be a Norrish type II photo-degradation. The detection among the reaction products of an aldehyde with one carbon atom less than the olefin produced by the Norrish type II photo-degradation suggests a photolytic decomposition of 1-alkenes, resulting in the formation of highly reactive compounds capable of abiotic reactions in the electronic ground state with a variety of organic compounds occurring in seawater.

Oxidation of cyclododecane in the presence of anthraquinone and o-nitrophenol : B. Ya. Ladygin, L. G. Bodachenko and V. N. Shurayeva, Neftekhimiya 23, No. 5, 664–669, 1983

Oxidation of cyclododecane in the presence of anthraquinone and o-nitrophenol : B. Ya. Ladygin, L. G. Bodachenko and V. N. Shurayeva, Neftekhimiya 23, No. 5, 664–669, 1983

Polymerization of 10-vinylphenthiazine in presence of orgamic π-acids

The polymerization of 10-vinyl phenthiazine has been studied in presence of anthraquinone, p-toluquinone, p-benzoquinone, 2,4,7-trinitrofluorenone, 7,7,8,8-tetracyanoquinodimethane. It has been established that the process of initiation of polymerization includes the stages of formation of the donor-acceptor complex and its dissociation into ion-radicals and recombination of the cation-radical of the monomer into the di-cation. The polymer chain grows by a cationic mechanism. A decisive influence on the molecular weights of the polymer is exerted by the mobile equilibrium of the ion pairs ↔ macrocation and the nature of the acceptor used. The main process of limitation of growth of the polymer chain is the reaction of chain transfer to the monomer.

Carbohydrate stabilization in wood by quinones and oxygen

Spruce meal, impregnated with magnesium sulfate to suppress the depolymerization of the carbohydrates by oxygen, was treated with 1 M sodium hydroxide at 100°C in the presence of anthraquinone (AQ) or anthraquinone-2-sulfonic acid (AMS). A decreased loss of carbohydrates obtained in the presence of oxygen is related to an increased conversion of the reducing sugar end groups to aldonic acid end groups. Larger effects of oxygen were obtained with AMS compared to AQ.

Thermal degradation of poly(vinyl chloride) in presence of additives part III. Studies in molecular weight distribution

AbstractThe changes in molecular weight and molecular weight distribution of PVC degraded in presence of maleic anhydride, benzoquinone and anthraquinone were studied by gel permeation chromatography. Chain scission and crosslinking reactions were indicated on the basis of M̄n and M̄w of degraded samples. Crosslinking was predominant when degradation was carried out in presence of anthraquinone.

Alkali Treatment of Glycolaldehyde, Glucose and Cellobiose in the Presence of Anthraquinone.

Alkali Treatment of Glycolaldehyde, Glucose and Cellobiose in the Presence of Anthraquinone.

Carbohydrate stabilization with anthraquinone during alkaline pulping

Treatment of wood meal with aqueous alkali in the presence of anthraquinone at 80°C leads to a conversion of reducing hexose end groups in the polysaccharides to mannonic and gluconic acid end groups. Xylose end groups are oxidized to xylonic and lyxonic acid groups. This leads to a stabilization of the polysaccharides against endwise alkaline degradation.

Studies on the Thermal Polymerization of Methyl Linoleate. V

Anthraquinone has been recognized as an effective catalyst for the thermal dimerization and the formation of conjugated isomers of methyl linoleate. From the results of analysis of kinetic data obtained, the mechanism of thermal dimerization of methyl Linoleate in the presence of anthraquinone is proposed as follows : The anthraquinone draws off a hydrogen atom from methyl linoleate molecule thus forming the radicals, which in turn produce either dimer by the radical-addition reaction or conjugated isomers of methyl linoleate. Then, the conjugated isomers and the linoleate dimerize by the Diels-Alder reaction, where the trans, trans-conjugated isomer acts as diene, and the trans, trans-, the cis, trans-conjugated isomer or the linoleate act as dienophile. Besides these reactions, the formation of octadecenoate also occurs.

Whisker Formation in the Presence of Anthraquinone

IT has been shown1 that nitrogen-substituted amino-anthraquinone compounds prepared by vacuum deposition in the form of solid films on quartz can crystallize when stored in the dark at room temperature. Similar experiments with impure aminoanthraquinone derivatives containing anthraquinone showed that whiskers2 also grow from the surface of the film. When these substances were purified and freed from anthraquinone before deposition, however, no whiskers were formed when the solid films were stored; nor was it possible to grow whiskers from films containing only anthraquinone. Subsequent attempts to investigate whisker formation were made with films prepared from mixtures of the purified aminoanthraquinone compound and pure anthraquinone.