Direct method for the determination of phenolic hydroxyl groups in pulp

Holzforschung ◽  
2007 ◽  
Vol 61 (6) ◽  
pp. 623-627 ◽  
Author(s):  
Tiina Liitiä ◽  
Tarja Tamminen
Keyword(s):  
Direct Method ◽  
Total Content ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Group ◽  
Total Phenolic ◽  
Hydroxyl Groups ◽  
Peroxide Bleaching ◽  
Uv Reflectance ◽  
Phenolic Hydroxyl Groups ◽  
Reflectance Measurements

Abstract For evaluation of changes in phenolic lignin units during kraft pulping and bleaching, a direct method based on UV reflectance measurements of pulp handsheets was tested. Similar trends in total phenolic hydroxyl-group contents were evident when UV reflectance results for isolated lignins and pulp sheets were compared. This direct method gave reliable results after alkaline cooking, oxygen delignification, and bleaching stages followed by alkaline extraction (DE, ZE). However, the phenolic content obtained after peroxide bleaching (QP) was over-estimated. This may be due to alkali-induced reactions during pH adjustment of the sheets for measurement concomitant with ionisation of the phenolic hydroxyl groups. Otherwise, this direct method based on UV reflectance measurements is a promising new approach for determining the total content of phenolic lignin units in pulp sheets without isolating the lignin.

Methylation of Phenolic Hydroxyl Group and Demethylation of Anisoles

2009 ◽  
Vol 2009 (4) ◽  
pp. 229-230 ◽  
Author(s):  
Nobuhiro Sato ◽  
Hiroyuki Endo
Keyword(s):  
Microwave Heating ◽  
Room Temperature ◽  
Reverse Reaction ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Phenolic Hydroxyl Groups ◽  
Phenyl Ethers ◽  
Methyl Phenyl

A mild methylation of phenolic hydroxyl groups with iodomethane was enabled in the presence of sodium bis(trimethylsilyl)amide at room temperature. The reverse reaction, namely demethylation of methyl phenyl ethers, was easily achieved by microwave heating with neat iodotrimethylsilane.

Effect of reserpine on the structure–activity relationships for the inhibition of noradrenaline uptake in adrenergic nerves in rat and rabbit ventricle by phenethylamines

1977 ◽  
Vol 55 (2) ◽  
pp. 196-205 ◽  
Author(s):  
D. M. Paton ◽  
D. S. Golko
Keyword(s):  
Phenolic Hydroxyl ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Noradrenaline Uptake ◽  
Inhibitory Potency ◽  
Sympathomimetic Amines ◽  
Structure Activity Relationships ◽  
Structure Activity ◽  
Phenolic Hydroxyl Groups ◽  
Inhibitory Agents

Ventricular tissue from the hearts of normal and reserpine-pretreated rats and rabbits were exposed to pargyline, tropolone, and hydrocortisone to inhibit monoamine oxidase (EC 1.4.3.4), catechol-O-methyltransferase (EC 2.1.1.6), and extraneuronal uptake, respectively. To examine the structure–activity relationships for inhibition of noradrenaline uptake, the inhibition of the 10-min uptake of (−)-[3H]noradrenaline by sympathomimetic amines was determined and ID50 values calculated. In reserpine-pretreated tissues, the most potent inhibitory agents studied were amines lacking phenolic hydroxyl groups (i.e., β-phenethylamine, (+)- and (−)-amphetamine). Addition of one or two phenolic hydroxyl groups, a β-hydroxyl group, or an N-methyl group generally decreased inhibitory potency, while α-methylation had little effect. Amines with large N-substitution and phenolic O-methyl groups were the least potent inhibitory agents. The stereoisomers of amphetamine, noradrenaline, and metaraminol did not differ in potency. However, the stereoisomers of ephedrine did, the order of potency being (−)-ephedrine > (±)-ephedrine > (+)-ψ-ephedrine > (−)-ψ-ephedrine. These structure–activity relationships are the same as those previously found for the acceleration of efflux of extragranular noradrenaline. Amines also released (−)-[3H]noradrenaline from reserpine-pretreated tissues. Results obtained using ventricles from nonreserpinized rats and rabbits showed two important differences. Firstly, sympathomimetic amines were much less potent releasers of (−)-[3H]noradrenaline from such tissues. Secondly, amines lacking phenolic hydroxyl groups were, on the average, five- to seven-fold less potent as inhibitors of (−)-[3H]-noradrenaline uptake. However, the inhibitory potencies of phenolethylamines and catecholamines were generally similar to those found in reserpine-pretreated tissues. These studies have demonstrated that reserpine pretreatment potentiates the inhibitory potency of phenethylamines and phenylethanolamines.

scholarly journals Transparent Cellulose/Technical Lignin Composite Films for Advanced Packaging

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1455 ◽  
Author(s):  
Guo ◽  
Tian ◽  
Shen ◽  
Yang ◽  
Long ◽  
...  
Keyword(s):  
Composite Films ◽  
Deep Eutectic Solvent ◽  
Value Added ◽  
Phenolic Hydroxyl ◽  
Total Phenolic ◽  
Hydroxyl Groups ◽  
Uv Shielding ◽  
Technical Lignin ◽  
Phenolic Hydroxyl Groups ◽  
Technical Lignins

Although recent work has shown natural lignin products are promising to fabricate various polymer based functional composites, high-value applications were challenged by their structural complexity and inhomogeneity. This work specially assessed the potential of four technical lignins for cellulose based functional films production. These four technical lignins were obtained by emerging pretreatment systems, i.e., lactic acid-betaine deep eutectic solvent (DES), ethanol organosolv, soda/anthraquinone (Soda/AQ) and the sodium salicylate hydrotrope, and their phenolic substructures were comparatively identified by prevalent 31P NMR technique. The influence of lignin chemical structure on the antioxidant potential and UV-shielding performance of the prepared cellulose/technical lignin composite films were assessed. Results showed severe organosolv and soda/AQ pretreatment produced technical lignins with higher total phenolic hydroxyl groups (3.37 and 3.23 mmol g-1 respectively), which also exhibited higher antioxidant activities. The composite films could effectively block the ultraviolet lights especially for UVB region (ultraviolet B, 280–315 nm) at only 5 wt.% lignin content. The contribution of lignin phenolic substructures to both antioxidant activity and UV-shielding property from high to low was syringyl > guaiacyl > p-hydroxyphenyl phenolic hydroxyl groups. This work provided some useful information that could facilitate upstream lignin extraction or downstream value-added applications.

scholarly journals Synthesis of Azacalixarenes and Development of Their Properties

Molecules ◽  
2021 ◽  
Vol 26 (16) ◽  
pp. 4885
Author(s):  
Hiroyuki Takemura
Keyword(s):  
Nitrogen Atom ◽  
Weak Interactions ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Side Chains ◽  
Simultaneous Presence ◽  
Basic Nitrogen ◽  
Phenolic Hydroxyl Groups ◽  
Deep Cavities

This review focuses on the synthesis, structure, and interactions of metal ions, the detection of some weak interactions using the structure, and the construction of supramolecules of azacalixarenes that have been reported to date. Azacalixarenes are characterized by the presence of shallow or deep cavities, the simultaneous presence of a basic nitrogen atom and an acidic phenolic hydroxyl group, and the ability to introduce various side chains into the cyclic skeleton. These molecules can be given many functions by substituting groups on the benzene ring, modifying phenolic hydroxyl groups, and converting side chains. The author discusses the evidence of azacalixarene utilizing these characteristics.

scholarly journals Phenolic Hydroxyl Groups in the Lignin Polymer Affect the Formation of Lignin Nanoparticles

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1790
Author(s):  
Jae Hoon Lee ◽  
Tae Min Kim ◽  
In-Gyu Choi ◽  
Joon Weon Choi
Keyword(s):  
Solvent Extraction ◽  
Colloidal Stability ◽  
Molecular Size ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Nanoprecipitation Method ◽  
Phenolic Hydroxyl Groups ◽  
Soda Lignin

Alkaline soda lignin (AL) was sequentially fractionated into six fractions of different molecular size by means of solvent extraction and their phenolic hydroxyl groups were chemoselectively methylated to determine their effect on nanoparticle formation of lignin polymers. The effect of the lignin structure on the physical properties of nanoparticles was also clarified in this study. Nanoparticles were obtained from neat alkaline soda lignin (ALNP), solvent-extracted fractions (FALNPs, i.d. 414–1214 nm), and methylated lignins (MALNPs, i.d. 516–721 nm) via the nanoprecipitation method. Specifically, the size properties of MALNPs showed a high negative correlation (R2 = 0.95) with the phenolic hydroxyl group amount. This indicates that the phenolic hydroxyl groups in lignin could be influenced on the nucleation or condensation during the nanoprecipitation process. Lignin nanoparticles exhibited high colloidal stability, and most of them also showed good in vitro cell viability. This study presents a possible way to control nanoparticle size by blocking specific functional groups and decreasing the interaction between hydroxyl groups of lignin.

Determination of Phenolic Hydroxyl Groups in Lignin by Combined Use of 1H NMR and UV Spectroscopy

Holzforschung ◽  
1999 ◽  
Vol 53 (5) ◽  
pp. 529-533 ◽  
Author(s):  
Eija Tiainen ◽  
Torbjörn Drakenberg ◽  
Tarja Tamminen ◽  
Kirsi Kataja ◽  
Anneli Hase
Keyword(s):  
Uv Spectroscopy ◽  
Spectroscopic Properties ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Model Compounds ◽  
H Nmr ◽  
Combined Use ◽  
Phenolic Hydroxyl Groups ◽  
The Difference

Summary Two independent spectroscopic methods are presented and compared for the quantitation of the phenolic hydroxyl groups in lignins. The combined information is used to further elucidate the character of the lignin samples examined. The UV method is based on the difference of the spectroscopic properties of the ionised and the nonionised phenol. The method using 1H NMR spectroscopy is based on the exchange of phenolic protons in D2O. The difference in integrated proton intensities in the sample dissolved in DMSO and the sample with additional 20% D2O is proportional to the phenolic protons. The method based on UV spectroscopy uses differences in the maxima close to 300 nm and 350 nm of the sample dissolved in alkali and the neutral sample. The results using the two independent methods are in agreement for milled wood lignin, for kraft lignin and for model compounds carrying one aromatic hydroxyl group. For modified lignins and for model compounds with more than one aromatic hydroxyl group, the UV method gives too low values for phenolic hydroxyl groups. The combined results obtained by the two methods however provide information of the total amount of the phenolic groups and of the nature of the phenolic structure formed by the lignin refining.

scholarly journals Reactivity of Aliphatic and Phenolic Hydroxyl Groups in Kraft Lignin towards 4,4′ MDI

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2131
Author(s):  
Leonardo Dalseno Antonino ◽  
Júlia Rocha Gouveia ◽  
Rogério Ramos de Sousa Júnior ◽  
Guilherme Elias Saltarelli Garcia ◽  
Luara Carneiro Gobbo ◽  
...  
Keyword(s):  
Experimental Work ◽  
Chemical Structure ◽  
31P Nmr ◽  
Kraft Lignin ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Diphenylmethane Diisocyanate ◽  
Complex Chemical ◽  
Heterogeneous Reactivity ◽  
Phenolic Hydroxyl Groups

Several efforts have been dedicated to the development of lignin-based polyurethanes (PU) in recent years. The low and heterogeneous reactivity of lignin hydroxyl groups towards diisocyanates, arising from their highly complex chemical structure, limits the application of this biopolymer in PU synthesis. Besides the well-known differences in the reactivity of aliphatic and aromatic hydroxyl groups, experimental work in which the reactivity of both types of hydroxyl, especially the aromatic ones present in syringyl (S-unit), guaiacyl (G-unit), and p-hydroxyphenyl (H-unit) building units are considered and compared, is still lacking in the literature. In this work, the hydroxyl reactivity of two kraft lignin grades towards 4,4′-diphenylmethane diisocyanate (MDI) was investigated. 31P NMR allowed the monitoring of the reactivity of each hydroxyl group in the lignin structure. FTIR spectra revealed the evolution of peaks related to hydroxyl consumption and urethane formation. These results might support new PU developments, including the use of unmodified lignin and the synthesis of MDI-functionalized biopolymers or prepolymers.

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