Dioxane lignins of kenaf bast and tow

Summary 1. Dioxane lignins have been isolated from the outer (bast) and inner (tow) parts of kenaf of the variety Uzbekskii 15–74, and the semiempirical formulas of the phenylpropane structural units of these dioxanes have been calculated on the basis of elementary and functional analyses.2. It has been shown by measurements of molecular-weight distribution that the DLAKK was more polydisperse than the DLALK.3. A study of the products of alkaline nitrobenzene oxidation and of decomposition by metallic sodium in liquid ammonia has shown that the DLAKK and DLALK were constructed of p-coumaryl, guaiacyl, and syringyl structural units, with the latter predominating.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 74–82, January–February, 1979.     

Vibrational Spectroscopic Analyses and Imaging of the Early Middle Ages Hemp Bast Fibres Recovered from Lake Sediments

Fourier Transform Infrared (FT-IR) spectroscopy and imaging combined with hierarchical cluster analysis (HCA) was applied to analyse biochemical properties of Early Middle Ages hemp (Cannabis sativa L.) bast fibres collected from lake bottom sediment of lake Słone. The examined plant macrofossil material constitutes residues of the hemp retting process that took place in the 7th–8th century. By comparison of three samples: untreated isolated bast fibres, and fibres incubated overnight at 4 and 37 °C, we were able to mimic the retting conditions. Using FT-IR qualitative and semi-quantitative assessment of the primary polysaccharides content, total protein content, and their spatial distribution was performed within the hemp fibres. The concentration of cellulose remained vastly unchanged, while the concentration of lignin and pectin was the highest in the untreated sample. The spatial distributions of compounds were heterogeneous in the untreated and 4 °C-incubated samples, and homogenous in the specimen processed at 37 °C. Interestingly, a higher amide content was detected in the latter sample indicating the highest degree of enzymatic degradation. In this study, we show that the spectroscopic methods allow for a non-destructive evaluation of biochemical composition of plant fibres without preparation, which can be an appropriate approach for studying ancient plant remains.     

Characterization of cellulose nanofibrils prepared by direct TEMPO-mediated oxidation of hemp bast

Hemp bast (α-cellulose 79.4%, Klason lignin 4.9%) was directly oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation in water at pH 10 and room temperature for 2 h. The level of added NaClO in oxidation varied from 5 to 30 mmol/g (based on dry weight of hemp bast). Weight recovery ratios of the TEMPO-oxidized hemp bast celluloses were in the range of 81–91%, and their carboxylate contents increased up to 1.2 mmol/g with the increased NaClO addition level. The lignin contents decreased to 0.5–0.9% after oxidation, and the viscosity-average degrees of polymerization decreased from 1100 to 560 because of depolymerization during oxidation. Thus, direct TEMPO-mediated oxidation of hemp bast introduced a significant number of carboxylate groups and simultaneously achieved sufficient delignification. Small amounts of xylose, mannose, and rhamnose originating from hemicelluloses remained in the TEMPO-oxidized hemp bast samples prepared by oxidation with 5–20 mmol/g NaClO. However, oxidation with 30 mmol/g NaClO completely removed these hemicellulose-originating sugars, and produced almost pure TEMPO-oxidized cellulose. When TEMPO-oxidized hemp bast samples were mechanically disintegrated in water, their nanofibrillation yields were 58–65%. After removal of unfibrillated fractions by centrifugation, transparent dispersions showed birefringence when observed between cross-polarizers, while atomic force microscopy images showed near-individually dispersed nanofibril elements with widths of ~2 nm.     

Equations for the Molecular Mass Distribution of Hydrocarbons Formed in CO Hydrogenation on a Cobalt–Zirconium Catalyst

A mathematical model for Fischer–Tropsch synthesis is proposed. The model takes into account the most common deviations from classical Anderson–Schulz–Flory distribution and adequately describes the experimental molecular mass distributions of hydrocarbons formed in carbon monoxide hydrogenation on a cobalt catalyst supported on the zirconium form of silica gel.     

Voltammetric Determination of Sulfide Ions

Procedures were proposed for the voltammetric determination of S^2– at a mercury-film electrode. They are based on the oxidation of S^2– at –0.79 to –0.80 V and on the reduction of HgS, the product of the oxidation of S^2–, at –0.76 to –0.96 V in a 1 M NaOH solution. The anodic and cathodic currents are linear functions of S^2– concentration in the ranges from 1 × 10^–5 to 1 × 10^–4 M and from 2 × 10^–6 to 1 × 10^–4 M, respectively.     

Voltammetric Determination of Rubeanic Acid

Procedures for the voltammetric determination of rubeanic acid (RA) at a mercury-film electrode were proposed. They are based on the oxidation of RA at –0.70 to –0.80 V or on the reduction of mercury sulfide, the product of RA oxidation, at –0.82 to –0.85 V (versus a saturated silver–silver chloride electrode) in a 1 M NaOH solution. The oxidation and reduction currents are linear functions of RA concentration in the ranges from 9 × 10^–6 to 3 × 10^–4 M and from 5 × 10^–6 to 3 × 10^–4 M, respectively.     

Improved method of obtaining piperitone

A new convenient variant of the reduction of thymol methyl ether by lithium and isopropanol in the presence of ethylenediamine at 80–85°C and a molar equivalent ratio of ether to alcohol to amine to metal of 1:(8–12):(2.5–3):(4–6) has been developed. The proposed method permits the yield of piperitone to be doubled in comparison with known methods.I. N. Ul'yanov Chuvash State University, Cheboksary. Translated from Khimiya Prirodnykh Soedinenii, Nos. 3,4, pp. 335–338, May–August, 1992.     

Improved Hydrophobicity of Macroalgae Biopolymer Film Incorporated with Kenaf Derived CNF Using Silane Coupling Agent

Hydrophilic behaviour of carrageenan macroalgae biopolymer, due to hydroxyl groups, has limited its applications, especially for packaging. In this study, macroalgae were reinforced with cellulose nanofibrils (CNFs) isolated from kenaf bast fibres. The macroalgae CNF film was after that treated with silane for hydrophobicity enhancement. The wettability and functional properties of unmodified macroalgae CNF films were compared with silane-modified macroalgae CNF films. Characterisation of the unmodified and modified biopolymers films was investigated. The atomic force microscope (AFM), SEM morphology, tensile properties, water contact angle, and thermal behaviour of the biofilms showed that the incorporation of Kenaf bast CNF remarkably increased the strength, moisture resistance, and thermal stability of the macroalgae biopolymer films. Moreover, the films’ modification using a silane coupling agent further enhanced the strength and thermal stability of the films apart from improved water-resistance of the biopolymer films compared to unmodified films. The morphology and AFM showed good interfacial interaction of the components of the biopolymer films. The modified biopolymer films exhibited significantly improved hydrophobic properties compared to the unmodified films due to the enhanced dispersion resulting from the silane treatment. The improved biopolymer films can potentially be utilised as packaging materials.     

Infrared spectra of cyclic ethers and their derivatives

The IR spectra of six monosubstituted and of four 2,6-disubstituted 1,4-dioxanes have been studied in the 650–1800cm^–1 region. The assignment of the bands due to the vibrations of the 1,4-dioxane ring and to the deformation vibrations of the methylene groups of the ring is given. The appearance of a whole series of new absorption bands on passing from unsubstituted 1,4-dioxane to its derivatives is explained by the change in the symmetry of the molecule and the removal of the prohibition from the vibrations previously inactive in the IR spectra connected with this reduction in symmetry. It is proposed to use, in order to confirm the presence of a 1,4-dioxane ring in a molecule from the results of IR spectroscopy, not only the 1126-cm^–1 band but the whole group of bands lying in the frequency ranges 800–950, 1000–1150, and 1200–1300 cm^–1.For part I, see [3].     

Flow injection chemiluminescence determination of naftopidil based on potassium permanganate oxidation in the presence of formaldehyde or formic acid

A flow injection method is proposed for the determination of naftopidil based upon the oxidation by potassium permanganate in a sulfuric acid medium and sensitized by formaldehyde and formic acid. The optimum chemical conditions for the chemiluminescence emission were 0.25 mM potassium permanganate and 4.0 M sulfuric acid. Two manifolds were tested and instrumental parameters such as the length of the reactor, injection volume and flow rate were compared. When using the selected manifold in the presence of 0.4 M formaldehyde, naftopidil gives a second-order calibration graph over the concentration range 0.1–40.0 mg L^–1 with a detection limit calculated (as proposed by IUPAC) of 92.5 ng mL^–1 and a standard deviation of 0.12 mg mL^–1 for ten samples of 10.0 mg L^–1 naftopidil. In the presence of 1.15 M formic acid, naftopidil gives a second-order calibration graph over the concentration range 0.05–40.0 mg L^–1 with a detection limit of 14.2 ng mL^–1 and a standard deviation of 0.37 mg mL^–1 for ten samples of 10.0 mg L^–1 naftopidil. In both cases, the determination is free from interferences from common excipients such as sucrose, glucose, lactose, starch and citric acid.     

Amination of biologically active guaianolides containing an α-methylene-γ-lactone grouping

A method is proposed for freeing total plant phospho- and phosphonolipids from impurities.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Priorodynkh Soedinenii, No. 6, pp. 785–788, November–December, 1988.     

Structure of artabin

Summary FromArtemisia absinthium L. a new sesquiterpene lactone of the germacrane type — artabin — has been isolated. Structure I is proposed for it.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedineii, No. 6, pp. 691–694, November–December, 1970.     

Catalytic hydroamination of furfuryl and tetrahydrofurfuryl alcohols with nitriles

Reaction of furfuryl and tetrahydrofurfuryl alcohols with nitriles over copper oxide catalysts under a hydrogen pressure of 15 atm at a temperature of 230C gives N-alkylfurfuryl- (yield 46–50%) and N-alkyl-tetrahydrofurfurylamines (49–53%), and N-alkylpiperidines (28–41%). A reaction mechanism is proposed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 23–26, January, 1988.     

Guaiol and hydroxyaromatic acids of Ferula ferulaeoides

Summary A method is proposed for freeing plant phospholipids from carbohydrates; silica gel has been used as adsorbent.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 570–572, September–October, 1975.     

New method for the 1-deacetylation of peracetates of aminosugars

A method for the selective O-deacetylation at the glycosidic centers of aminosugar peracetates is proposed.M. V. Frunze Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 177–179, March–April, 1994.