scholarly journals Reactivity of Polymers on Exposure to Nitrogen Dioxide

2010 ◽  
Vol 4 (4) ◽  
pp. 281-290
Author(s):  
Evgeny Davydov ◽  
◽  
Irina Gaponova ◽  
Georgy Pariiskii ◽  
Tatyana Pokholok ◽  
...  
Keyword(s):  
Free Radical ◽  
Nitrogen Dioxide ◽  
Chemical Structure ◽  
Elevated Temperatures ◽  
Carbon Chain ◽  
Hydroxyl Groups ◽  
Double Bonds ◽  
Simple Method ◽  
Alkyl Radicals

The mechanism of reactions of nitrogen dioxide with polymers of different classes is considered. In reactions with carbon-chain polymers at 298 K, nitrogen dioxide can only add to extrinsic double bonds that are formed in the synthesis of the polymers. The mechanism of reactions of nitrogen dioxide with polymers of different classes is considered. In reactions with carbon-chain polymers at 298 K, nitrogen dioxide can only add to extrinsic double bonds that are formed in the synthesis of the polymers. These reactions resulted in dinitro compounds and nitro nitrites. At elevated temperatures, carbonyl and hydroxyl groups are formed in these polymers along with nitration products. Active participants of NO2 reactions with rubbers are double bonds converting into nitroalkyl and alkyl radicals initiating then free radical conversions of these polymers. Polymers containing amide, urethane and imide groups are rather sensitive to NO2. These materials undergo essential changes in the chemical structure with formation of stable nitrogen-containing radicals. The reactions of nitrogen dioxide provide a simple method of the spin-labeled polymer preparation.

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.

scholarly journals The structure of novel C35 pentacyclic terpenes from Acetobacter xylinum

1973 ◽  
Vol 135 (1) ◽  
pp. 133-143 ◽  
Author(s):  
Hans J. Förster ◽  
Klaus Biemann ◽  
W. Geoffrey Haigh ◽  
Neil H. Tattrie ◽  
J. Ross Colvin
Keyword(s):  
High Resolution ◽  
High Resolution Mass Spectrometry ◽  
Carbon Chain ◽  
Acetobacter Xylinum ◽  
Mass Spectrometric ◽  
Hydroxyl Groups ◽  
Mass Spectral Data ◽  
Mass Spectral ◽  
High Resolution Mass ◽  
Resolution Mass

A novel C35 terpene and its monounsaturated analogue were isolated from cultures of Acetobacter xylinum, together with traces of their C36 homologues. These substances were found to be hopane derivatives substituted by a five-carbon chain bearing four vicinal hydroxyl groups. For the parent hydrocarbon the term bacteriohopane is proposed. The elucidation of the structures utilized high-resolution mass spectrometry of the terpenes, degradation to C32 hydrocarbons and detailed mass-spectrometric comparison of these with C32 hydrocarbons synthesized from known pentacyclic triterpenes. High-resolution mass-spectral data of the terpenes are presented. N.m.r. data are in agreement with the proposed structures, which are further supported by the isolation from the same organism of 22-hydroxyhopane and derivative hopene(s).

Evaluation of Biodegradability of Amine Collectors

2010 ◽  
Vol 113-116 ◽  
pp. 267-271 ◽  
Author(s):  
Heng Zhen Yan ◽  
Wen Qi Gong ◽  
Guang Jun Mei ◽  
Xiao Ye Liu ◽  
Shao Hua Chen
Keyword(s):  
Chemical Structure ◽  
Ester Group ◽  
Carbon Chain ◽  
Ammonium Bromide ◽  
Evaluation Standards ◽  
Testing Method

Amine collectors are widely used as oxidized ore collectors.Based on OECD 301B testing method, the biodegradability of amine collectors were analyzed and evaluated, and the values of IB of lauryl amine, octadecylamine, laurtrimonium chloride, lauryl trimethyl ammonium bromide, decane-propyl ether amine and dodecyl propyl ether amine were 173.4, 162.2, 164.6, 171.2, 160.8 and 149.4, respectively. The biodegradation of six test substances all exceeded 10% in 10 days, and all up to over 50% within 28 days. Considering comprehensively the two evaluation standards, the six amine collectors are all biodegradable. Evaluation of the biodegradability of amine collectors provides information that the chemical structure influences the biodegradability of amine collectors. It seems that the existence of ester group decreases the biodegradability of ether amine, and the shorter the carbon chain, the greater the biodegradation occurred.

A Simple Method for the Characteristic Differentiation of Antibiotics by TLC-Bioautography in Graded Concentration of Ammonium Chloride

1988 ◽  
Vol 51 (10) ◽  
pp. 786-789 ◽  
Author(s):  
FUSAO KONDO
Keyword(s):  
Laboratory Test ◽  
Ammonium Chloride ◽  
Chloride Solution ◽  
Chemical Structure ◽  
Characteristic Change ◽  
Routine Laboratory ◽  
Simple Method ◽  
Tetracycline Antibiotics ◽  
Tlc Bioautography ◽  
Rf Values

A simple classification method for 24 known antibiotics by TLC-bioautographic procedure was developed. The approach used was to change the Rf values in seven TLC systems with an ammonium chloride solution in a graded concentration range (0.5, 1, 2, 3, 5, 10 and 20%). The antibiotics were divided into four groups (A to D) showing the characteristic behavior of Rf values corresponding to similarities in chemical structure: β-lactam, aminoglycoside, macrolide and tetracycline antibiotics. TLC-bioautography helps to estimate the character of antibiotics and the characteristic change of Rf values may be very useful for classifying unknown residual antibiotics in animal samples as a routine laboratory test.

scholarly journals 3D Printed Chromophoric Sensors

Chemosensors ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 317
Author(s):  
Zachary Brounstein ◽  
Jarrod Ronquillo ◽  
Andrea Labouriau
Keyword(s):  
Thermal Stability ◽  
3D Printing ◽  
Material Properties ◽  
Chemical Structure ◽  
Elevated Temperatures ◽  
Advanced Manufacturing ◽  
Color Changes ◽  
Printed Sensors ◽  
3D Printed ◽  
Manufacturing Techniques

Eight chromophoric indicators are incorporated into Sylgard 184 to develop sensors that are fabricated either by traditional methods such as casting or by more advanced manufacturing techniques such as 3D printing. The sensors exhibit specific color changes when exposed to acidic species, basic species, or elevated temperatures. Additionally, material properties are investigated to assess the chemical structure, Shore A Hardness, and thermal stability. Comparisons between the casted and 3D printed sensors show that the sensing devices fabricated with the advanced manufacturing technique are more efficient because the color changes are more easily detected.

scholarly journals Antioxidant Activity of Quercetin: A Mechanistic Review

2016 ◽  
Vol 4 (12) ◽  
pp. 1134 ◽  
Author(s):  
Senay Ozgen ◽  
Ozgur Kivilcim Kilinc ◽  
Zeliha Selamoğlu
Keyword(s):  
Antioxidant Activity ◽  
Free Radical ◽  
Cardiovascular Diseases ◽  
Chemical Structure ◽  
Radical Scavenging ◽  
Antioxidant Property ◽  
Free Radical Scavenging ◽  
Polyphenolic Compounds ◽  
Structure And Properties ◽  
Treatment Of Diabetes

Flavones and flavonoids are known to have potent antioxidant activity due to intracellular free radical scavenging capacities. Flavonoids are found ubiquitously in plants as a member of polyphenolic compounds which share diverse chemical structure and properties. Quercetin is among the most efficient antioxidants of the flavonoids. The antioxidant property of quercetin has been highlighted in this review. These compounds have pivotal role in treatment of diabetes, cancers and some cardiovascular diseases.

Free Radical Addition of Butanethiol to Vegetable Oil Double Bonds

2009 ◽  
Vol 57 (4) ◽  
pp. 1282-1290 ◽  
Author(s):  
Grigor B. Bantchev ◽  
James A. Kenar ◽  
Girma Biresaw ◽  
Moon Gyu Han
Keyword(s):  
Free Radical ◽  
Vegetable Oil ◽  
Radical Addition ◽  
Double Bonds ◽  
Free Radical Addition

scholarly journals Advanced Analytical Methods for Phenolics in Fruits

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
Nesibe Ebru Kafkas ◽  
Müberra Kosar ◽  
Ayşe Tülin Öz ◽  
Alyson E. Mitchell
Keyword(s):  
Phenolic Compounds ◽  
Value Added ◽  
Biological Tissues ◽  
Carbon Chain ◽  
Polyphenolic Compounds ◽  
Hydroxyl Groups ◽  
Plant Metabolites ◽  
Secondary Plant Metabolites ◽  
Extraction Separation ◽  
Health Promoting

Phenolic compounds are a group of secondary plant metabolites, many with health-promoting properties that are present in all parts of plants. They have an aromatic structure, including either one or more hydroxyl groups giving them the ability to stabilize free radicals and protect biological tissues against damage related to reactive oxygen species. Phenolic compounds are concentrated in the fruit of plants, and therefore, the fruit can be an important dietary source of these phytochemicals, which exist as monomers, or bound to one another. Polyphenolic compounds are classified into different subclasses based upon the number of phenol ring systems that they contain, saturation, and length of the carbon chain that bind the rings to one another. The phenolic acids present in fruit tissues protect the plant against disease, infections, UV radiation, and insect damage. For this reason, the beneficiary effects of phenolic compounds are continually being investigated for their health-promoting properties and for meeting increased consumer demand for healthy nutritious food. Due to the functional properties of polyphenolic compounds, there is increased interest on improving extraction, separation, and quantification techniques of these valuable bioactive compounds, so they can be used as value-added ingredients in foods, pharmaceuticals, and cosmetics. This review provides information on the most advanced methods available for the analysis of phenolics in fruits.

scholarly journals Hydrophilicity and carbon chain length effects on the gas sensing properties of chemoresistive, self-assembled monolayer carbon nanotube sensors

2019 ◽  
Vol 10 ◽  
pp. 565-577 ◽  
Author(s):  
Juan Casanova-Cháfer ◽  
Carla Bittencourt ◽  
Eduard Llobet
Keyword(s):  
Carbon Nanotubes ◽  
Nitrogen Dioxide ◽  
Photoelectron Spectroscopy ◽  
Gas Sensing ◽  
Carbon Chain ◽  
Head Group ◽  
Carbon Chain Length ◽  
Sensing Properties ◽  
Gas Sensing Properties ◽  
Self Assembled

Here we describe the development of chemoresistive sensors employing oxygen-plasma-treated, Au-decorated multiwall carbon nanotubes (MWCNTs) functionalized with self-assembled monolayers (SAMs) of thiols. For the first time, the effects of the length of the carbon chain and its hydrophilicity on the gas sensing properties of SAMs formed on carbon nanotubes are studied, and additionally, the gas sensing mechanisms are discussed. Four thiols differing in the length of the carbon chain and in the hydrophobic or hydrophilic nature of the head functional group are studied. Transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy are used to analyze the resulting gas-sensitive hybrid films. Among the different nanomaterials tested, short-chain thiols having a hydrophilic head group, self-assembled onto Au-decorated carbon nanotubes were most responsive to nitrogen dioxide and ethanol vapors, even in the presence of ambient humidity. In particular, this nanomaterial was about eight times more sensitive to nitrogen dioxide than bare Au-decorated carbon nanotubes when operated at room temperature. This response enhancement is attributed to the interaction, via strong hydrogen bonding, of the polar molecules tested to the polar surface of hydrophilic thiols. The approach discussed here could be extended further by combining hydrophilic and hydrophobic thiol SAMs in Au-MWCNT sensor arrays as a helpful strategy for tuning sensor response and selectivity. This would make the detection of polar and nonpolar gas species employing low-power gas sensors easier, even under fluctuating ambient moisture conditions.

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