The use of cerimetric method for phenolic hydroxyl determination in analytical practice

2020 ◽  
Vol 86 (5) ◽  
pp. 11-15
Author(s):  
I. V. Karandi ◽  
A. G. Buyanovskaya
Keyword(s):  
Potentiometric Titration ◽  
High Strength ◽  
Strength Properties ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Group ◽  
Indicator Electrode ◽  
Hydroxyl Groups ◽  
Sulfuric Acid Medium ◽  
Cerium Sulfate

The possibility of using cerium (IV) sulfate as an oxidizing reagent in analysis of various organic compounds is considered and exemplified specifically in determination of phenolic hydroxyl group. Cerium sulfate quantitatively reacts with a phenolic hydroxyl group to form quinoid compounds. Techniques for determination of phenols of different structures (including perchlorinated and perfluorinated phenols) using potentiometric titration with a solution of cerium sulfate in a sulfuric acid medium with a redoxometric indicator electrode are proposed. The presence of the substituents with reducing properties in the aromatic ring interferes with the determination. Cerimetric potentiometric titration was also used to study the structure of polymers based on methylol derivatives of phenolphthalein which are crosslinking agents and serve to obtain thermostatic structural materials with high strength properties. It is shown that the methylol hydroxyl group, which is also quantitatively oxidized by cerium sulfate, can be determined simultaneously with a phenolic hydroxyl group. The results obtained by the proposed method of cerimetric titration and well-known method of acetylation appeared identical. The determined number of hydroxyl groups in the analyzed samples is indicative of the polymer structure. Proceeding from the technique of cerimetric titration we propose a method for determination of free xylenols in fire-resistant turbine oil. The developed technique is more rapid and less labor-consuming compared to generally accepted technique TU 3470.11335–07 based on the bromination of xylenols with a bromide-bromate mixture.

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 Cobalt(II) ion-selective electrode with solid contact

2008 ◽  
Vol 6 (4) ◽  
pp. 607-612 ◽  
Author(s):  
Cecylia Wardak
Keyword(s):  
Detection Limit ◽  
Response Time ◽  
Potentiometric Titration ◽  
Indicator Electrode ◽  
Solid Contact ◽  
Selective Electrode ◽  
Cobalt Ions ◽  
Real Samples ◽  
Nernstian Slope

AbstractA new all plastic sensor for Co2+ ions based on 2-amino-5 (hydroxynaphtyloazo-1′)-1,3,4 thiadiazole (ATIDAN) as ionophore was prepared. The electrode exhibits a low detection limit of 1.5 × 10−6 mol L−1 and almost theoretical Nernstian slope in the activity range 4.0 × 10−6–1 × 10−1 mol L−1 of cobalt ions. The response time of the sensor is less than 10 s and it can be used over a period of 6 months without any measurable divergence in potential. The proposed sensor shows a fairly good selectivity for Co(II) over other metal ions. The electrode was successfully applied for determination of Co2+ in real samples and as an indicator electrode in potentiometric titration of Co2+ ions with EDTA.

scholarly journals Application of Home Made Ag2S Electrode in Alkaline Media

1970 ◽  
Vol 8 (8) ◽  
pp. 69-72
Author(s):  
A Rajbhandari ◽  
AP Yadav ◽  
RR Pradhananga ◽  
K Manandhar ◽  
C Durante ◽  
...  
Keyword(s):  
Silver Nitrate ◽  
Potentiometric Titration ◽  
Pharmaceutical Preparation ◽  
Vitamin B1 ◽  
Alkaline Media ◽  
Indicator Electrode ◽  
Membrane Electrode ◽  
Thiamine Hydrochloride ◽  
Silver Sulphide

Home made silver sulphide ion selective electrode was prepared and applied for argentometric titration in alkaline media for the determination of thiamine hydrochloride.The amount of thiamine hydrochloride estimated from titration of ionisable chloride with silver nitrate was found to be 637 mg/g of the vitamin B1 tablet. This result is in agreement with the value obtained from ion chromatographic (IC) and cyclic voltammetric (CV) techniques. In presence of chloride from other sources, these techniques fail, but thiamine in pharmaceutical preparation, however, can be determined by potentiometric titration in highly alkaline medium using silver- sulphide membrane electrode with silver nitrate solution at which there is no interference due to the presence of chloride from other sources. The results showed that home made silver- sulphide electrode can be used as an indicator electrode for the potentiometric determination of thiamine in pharmaceutical preparation. Keywords: Silver sulphide electrode; Potentiometric titration; Thiamine; Vitamin B1. DOI: 10.3126/sw.v8i8.3853 Scientific World Vol.8(8) 2010 pp.69-72

scholarly journals Influence of Ethanol Organosolv Pulping Conditions on Physicochemical Lignin Properties of European Larch

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Markus Hochegger ◽  
Betty Cottyn-Boitte ◽  
Laurent Cézard ◽  
Sigurd Schober ◽  
Martin Mittelbach
Keyword(s):  
Reaction Temperature ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Group ◽  
Catalyst Loading ◽  
Hydroxyl Groups ◽  
European Larch ◽  
Molecular Weights ◽  
Organosolv Pulping ◽  
Lignin Fraction ◽  
Potential Applicability

Over the years, the organosolv pulping process has proven to be a valuable pretreatment method for various lignocellulosic feedstocks. The objective of this study was to characterize and assess the potential applicability of the organosolv lignin fraction from European larch sawdust, as no research has been conducted in this field so far. Eight different samples were prepared from the European larch sawdust under varied reaction conditions and one milled wood lignin sample as reference. The reaction temperature and sulfuric acid loading were varied between 420 and 460 K and 0.00 and 1.10% (w/w on dry wood basis) H2SO4, respectively. The antiradical potential (via DPPH• method), chemical structure (via ATR-FTIR, 1H NMR, 31P NMR, and thioacidolysis), as well as the molecular weight distribution of the isolated lignins were analyzed and compared. Results from thioacidolysis show a direct correlation between the amount of β-ether bonds broken and pulping process severity. Similarly, both antiradical potential and phenolic hydroxyl group content exhibit a direct relationship to reaction temperature and catalyst loading. On the contrary, the content of aliphatic hydroxyl groups and the average molecular weights both decreased with increasing process severity. The high content of phenolic hydroxyl groups and antioxidative potential of the larch organosolv fractions, especially for the sample isolated at 460 K and 1.10% H2SO4 loading, indicate good applicability as antioxidants as well as feedstocks for further downstream valorization and require additional research in this area.

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.

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.

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