Redox Systems in the Initiation of Radical Processes. Mechanism of Action

1959 ◽  
Vol 32 (1) ◽  
pp. 244-256
Author(s):  
B. A. Dolgoplosk ◽  
E. I. Tinyakova
Keyword(s):  
Free Radicals ◽  
Mechanism Of Action ◽  
Low Temperatures ◽  
Oxidation States ◽  
Reversible Systems ◽  
Redox Systems ◽  
The Third ◽  
Destructive Processes ◽  
Radical Processes ◽  
Variable Valency

Abstract The following redox systems capable of initiating radical polymerizations are discussed: (1) Systems of the first type, where the reaction leads to the formation of a single radical: (a) Mechanism of action of reversible systems involving dienols and salts of metals of variable valency. (b) Mechanism of the decomposition of hydroperoxides by the action of salts of metals of variable valency in their higher oxidation states. (2) Systems of the second type, where the reaction leads to the formation of two radicals. Mechanism of action and effectiveness of systems involving hydroperoxides, quinol, and sulfite. (3) Systems of the third type, in which the formation of free radicals is not directly linked to the redox process. Mechanism of action of systems involving diazoamino compounds and “polyamine” systems. (4) Crosslinking of unsaturated polymers at low temperatures by the action of redox systems. Transition from crosslinking to destructive processes in presence of oxygen.

The influence of humus acids of peloids and its components on free radical processes

2018 ◽  
Vol 64 (5) ◽  
pp. 429-432 ◽  
Author(s):  
N.P. Avvakumova ◽  
F.H. Kamilov ◽  
A.V. Zhdanova ◽  
I.A. Men’shikova ◽  
Yu.V. Zhernov ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Free Radical ◽  
Free Radical Oxidation ◽  
Albino Rats ◽  
Redox Systems ◽  
Radical Oxidation ◽  
The Third ◽  
Glutathione Peroxidases ◽  
Humus Acids ◽  
Radical Processes

The effect of individual components of humic substances of peloid on free radical oxidation processes has been investigated under conditions of oxidative stress induced in albino rats. Biological activity of peloids was determined using such parameters as the general antioxidant activity, activity superoxide dismutases, catalases and glutathione peroxidases on the third and tenth day of the experiment. Results indicate that the state of oxidative stress can be corrected on the third day of the experiment. Humic acids restore not only normal physiological redox systems, but also increase the activity of antioxidant enzymes on the 10th day.

Oxidation-Reduction Systems for Initiation of Radical Processes. VI. Systems Involving Oxygen for Initiation of Oxidative Degradation of Polymers

1959 ◽  
Vol 32 (1) ◽  
pp. 231-243 ◽  
Author(s):  
E. I. Tinyakova ◽  
B. A. Dolgoplosk ◽  
V. N. Reĭkh
Keyword(s):  
Free Radicals ◽  
Low Temperatures ◽  
Oxidative Degradation ◽  
Chain Process ◽  
Iron Salts ◽  
Oxidation Reduction ◽  
A Chain ◽  
Radical Processes ◽  
Effective Source ◽  
Hydrocarbon Media

Abstract 1. The mechanism of action of various oxidation-reduction systems containing organic reducing agents, iron salts, and oxygen, is investigated, and it is shown that in hydrocarbon media these systems are an effective source of free radicals at low temperatures. 2. The possibility of utilization of these systems for initiation of a chain process of oxidative degradation of unsaturated and some saturated polymers, at low temperatures, is shown.

Degradation of Rubber by Chemical Agents in Solution

1961 ◽  
Vol 34 (4) ◽  
pp. 1212-1219
Author(s):  
G. H. Foxley
Keyword(s):  
Free Radicals ◽  
Low Temperatures ◽  
Model Compound ◽  
Polymer Degradation ◽  
Chain Scission ◽  
Redox Systems ◽  
Chemical Agents ◽  
The Subject ◽  
Partial Fulfillment

Abstract It is clear that the subject of polymer degradation by chemical agents is an active branch of polymer chemistry. This is reflected in the large number of patents applying to polymer degradation and no attempt has been made to include every appropriate patent. Much of the comparative work is based on equal weights, rather than equal numbers of molecules, so that the true comparisons of the efficiency of peptizers are often difficult. It has been shown that polymer degradation can proceed via several mechanisms all of which involve free radicals and the main points can be summarized as follows :— In solutions at low temperatures the initiatory free radicals come from the added peptizer such as benzoyl peroxide or bis-azoisobutyronitrile. Although oxygen accelerates the reaction, it is not essential, and there is appreciable degradation in the absence of oxygen. Thiols are active only when oxygen is present even at high temperature. This is somewhat surprising, since the rubber radicals produced by thermal scission should be just as active as those produced by mastication and be capable of reaction with thiols, and serves to emphasize the importance of the role of oxygen in peptization by thiols and disulfides. Oxygen is also necessary for degradation by redox systems and in its absence structurizing takes place. The lack of work on triphenyl methane derivatives is somewhat surprising in view of the ease with which they undergo homolysis to give free radicals. However, it is not sufficient to introduce any type of free radical and expect degradation: stabilized free radicals are the best peptizers, unstable radicals can add to olefinic bonds and cause crosslinking rather than chain scission. Squalene has been used as a model compound for the study of the reactions of natural rubber with free radicals in a similar manner to the use of methylcyclohexene as a model compound for oxidation studies. This review forms part of a dissertation submitted in partial fulfillment of the requirements for the London University M.Sc. (External) Examination.

Mechanochemical Phenomena in Polymers. II. The Effects of Initiators and Inhibitors of Chain Processes

1963 ◽  
Vol 36 (2) ◽  
pp. 480-487
Author(s):  
E. V. Reztsova ◽  
B. T. Kipkina ◽  
G. L. Slonimskii
Keyword(s):  
Free Radicals ◽  
Fatigue Resistance ◽  
Substantial Effect ◽  
Chemical Bonds ◽  
Chain Processes ◽  
Radical Processes ◽  
Effect Of Inhibitors ◽  
Dynamic Fatigue

Abstract 1. The substantial effect of inhibitors and initiators of chain radical processes on the change in the properties of rubbers in milling, as well as on the resistance of vulcanizates to fatigue, has been shown. This indicates a mechanochemical mechanism for processing of polymers and in the fatigue of elastomers. The act of mechanical scission of chemical bonds, with the formation of free radicals which initiate the secondary chain processes, rests on these processes. 2. The possibility has been shown of regulating the properties of polymers during processing, and also of increasing the dynamic fatigue resistance of vulcanizates by incorporating small quantities of additives active in regard to free radicals.

scholarly journals How Aromatic Are Molecular Nanorings? The Case of a Six-Porphyrin Nanoring

2021 ◽  
Author(s):  
irene casademont-reig ◽  
Raúl Guerrero-Avilés ◽  
Eloy Ramos-Cordoba ◽  
Miquel Torrent-Sucarrat ◽  
Eduard Matito
Keyword(s):  
Low Temperatures ◽  
Ring Current ◽  
Computational Method ◽  
Oxidation States ◽  
Aromatic Rings ◽  
Persistent Currents ◽  
Conjugated Molecules ◽  
Strong Magnetic Fields ◽  
The Poor ◽  
Computational Calculations

<div> <div> <div> <p>Large conjugated rings give rise to novel promising structures that can sustain persistent currents at low temperatures even in the presence of strong magnetic fields. One of the most interesting such molecules was recently synthesized [Anderson et al., Nature, 2017, 541, 3512] in the form of a six-porphyrin nanoring structure, which, according to the authors, in its +6-oxidation state (c-P66+) sustained an aromatic ring current involving 78π electrons; one of the largest aromatic rings ever produced. In this paper, we have provided compelling evidence that this molecule is not aromatic, as it was incorrectly inferred from computational calculations that suffer from large delocalization errors. A thorough analysis of four oxidation states of the six-porphyrin nanoring re- veals that the main reason behind the poor aromaticity of these nanorings is the low delocalization in the transition from the porphyrins to the bridging butadiyne linkers, which disrupts the overall conjugated circuit. These results highlight the importance of choosing an adequate computational method to study large conjugated molecules and the appropriate aromaticity descriptors to identify the part of the molecule that is responsible for the loss of aromaticity. We believe the strategy here employed will be helpful in designing new large aromatic molecular nanorings. </p> </div> </div> </div>

scholarly journals Efektivitas Ekstrak Buah Merah (Pandanus conoideus De Vriese) Asal Kabupaten Poso Sebagai Alternatif Penurun Kadar Gula Darah

2017 ◽  
Vol 5 (4) ◽  
pp. 185
Author(s):  
Anang Wahid M. D. Diah ◽  
Ni Kadek Ana Diani ◽  
Minarni Rama Jura
Keyword(s):  
Free Radicals ◽  
Blood Sugar ◽  
Positive Control ◽  
Negative Control ◽  
Effective Concentration ◽  
Fruit Extract ◽  
Control Data ◽  
Significance Level ◽  
The Third ◽  
Sugar Levels

Bioactive compounds contained in red fruit (pandanus conoideus De Vriese) among others are flavonoids and tannins. The compounds are classified as very powerful antioxidants and can inhibit free radicals. This study aimed to determine the effective concentration of the red fruit extract from Poso as an alternative for lowering blood sugar levels. The separatin method used was boiling. The animals test were 15 male of mice (Mmus musculus) induced by ethylene diamine tetra acetic (EDTA). The mice were divided randomly into 5 groups with different treatments. The first, the second, and the third treatments were given red fruit extract each with a concentration of 10%, 20% and 30%. The fourth treatment was given glibenclamide suspension as a positive control, and the fifth treatments was given Na-CMC as a negative control. Data were analyzed using a statistical analysis of variance (Anova) test followed by Duncan test. The results showed that the preclinical test of red fruit extract reduced blood sugar levels of mice, and the most effective concentration was 20% as much as 68% (w/v) with significance level a = 0.05.

E.s.r. studies on free radicals generated in poly[p-(2-hydroxyethoxy) benzoic acid] fibres at low temperatures

Polymer ◽  
1981 ◽  
Vol 22 (9) ◽  
pp. 1267-1271 ◽  
Author(s):  
Toshihiko Nagamura ◽  
Kenneth Lawrence DeVries
Keyword(s):  
Free Radicals ◽  
Benzoic Acid ◽  
Low Temperatures

scholarly journals Mechanism of action of the third generation benzopyrans and evaluation of their broad anti-cancer activity in vitro and in vivo

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Alexander J. Stevenson ◽  
Eleanor I. Ager ◽  
Martina A. Proctor ◽  
Dubravka Škalamera ◽  
Andrew Heaton ◽  
...  
Keyword(s):  
Mechanism Of Action ◽  
Third Generation ◽  
The Third ◽  
Anti Cancer ◽  
Cancer Activity
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