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Academic literature on the topic 'Free radical'

Author: Grafiati

Published: 4 June 2021

Last updated: 9 June 2025

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Journal articles on the topic "Free radical"

1

Yañez Jaramillo, Lina M., Joy H. Tannous, and Arno de Klerk. "Persistent Free Radicals in Petroleum." Processes 11, no. 7 (July 11, 2023): 2067. http://dx.doi.org/10.3390/pr11072067.

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The persistent free radical content in petroleum is of the order 1018 spins/g (1 μmol/g), with higher and lower values found depending on origin and in different distillation fractions. The field of persistent free radicals in petroleum was reviewed with the aim of addressing and explaining apparent inconsistencies between free radical persistence and reactivity. The macroscopic average free radical concentration in petroleum is persistent over geological time, but individual free radical species in petroleum are short-lived and reactive. The persistent free radical concentration in petroleum can be explained in terms of a dynamic reaction equilibrium of free radical dissociation and association that causes a finite number of species at any given time to be present as free radicals. Evidence to support this description are observed changes in free radical concentration related to change in Gibbs free energy when the bulk liquid properties are changed and responsiveness of free radical concentration to dynamic changes in temperature. Cage effects, solvent effects, steric protection, and radical stabilization affect free radical reaction rate but do not explain the persistent free radical concentration in petroleum. The difference between persistent free radicals in straight-run petroleum and converted petroleum is that straight-run petroleum is an equilibrated mixture, but converted petroleum is not at equilibrium and the free radical concentration can change over time. Based on the limited data available, free radicals in straight-run petroleum appear to be part of the compositional continuum proposed by Altgelt and Boduszynski. Persistent free radical species are partitioned during solvent classification of whole oil, with the asphaltenes (n-alkane insoluble) fraction having a higher concentration of persistent free radicals than maltenes (n-alkane soluble) fraction. Attempts to relate persistent free radical concentration to petroleum composition were inconclusive.

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Kim, Eun-Kyung, and Mi Ryeong Song. "Factors Influencing the Level of Oxygen Free Radicals in Female Nursing Students." Global Journal of Health Science 11, no. 7 (May 15, 2019): 1. http://dx.doi.org/10.5539/gjhs.v11n7p1.

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This study was conducted to investigate the levels of oxygen free radicals and related health factors in 201 female nursing students. The questionnaire was completed by the participants and their oxygen free radical levels were measured by urine test. In this study, an oxygen free radical analyzer was used to measure oxygen free radical levels. The oxygen free radical analyzer analyzes the amount of oxygen free radicals in the body by measuring urinary malondialdehyde (MDA). To determine factors associated with oxygen free radical levels, multiple regression tests were conducted. Of the participants, 89.6% exhibited normal levels of oxygen free radicals and 10.4% had elevated levels. In this study, the factors that affected oxygen free radical levels were eating habit (&beta; = .20, p =. 003), fatigue (&beta; = .20, p = .004), and detox necessity (&beta; = .18, p = .006). In order to lower oxygen free radical levels of female nursing students, the areas of eating habit, fatigue, and detox must receive increased focus.

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3

Stevanovic, Jelka, Suncica Borozan, Slavoljub Jovic, and Igor Ignjatovic. "Physiology of free radicals." Veterinarski glasnik 65, no. 1-2 (2011): 95–107. http://dx.doi.org/10.2298/vetgl1102095s.

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Free radicals imply that every atom, molecule, ion, group of atoms, or molecules with one or several non-paired electrons in outer orbital. Among these are: nitrogenoxide (NO?), superoxide-anion-radical (O2?-), hydroxyl radical (OH?), peroxyl radical (ROO?), alcoxyl radical (RO?) and hydroperoxyl radical (HO2?). However, reactive oxygen species also include components without non-paired electrons in outer orbital (so-called reactive non-radical agents), such as: singlet oxygen (1O2), peroxynitrite (ONOO-), hydrogen-peroxide (H2O2), hypochloric acid (eg. HOCl) and ozone (O3). High concentrations of free radicals lead to the development of oxidative stress which is a precondition for numerous pathological effects. However, low and moderate concentrations of these matter, which occur quite normally during cell metabolic activity, play multiple significant roles in many reactions. Some of these are: regulation of signal pathways within the cell and between cells, the role of chemoattractors and leukocyte activators, the role in phagocytosis, participation in maintaining, changes in the position and shape of the cell, assisting the cell during adaption and recovery from damage (e.g.caused by physical effort), the role in normal cell growth, programmed cell death (apoptosis) and cell ageing, in the synthesis of essential biological compounds and energy production, as well as the contribution to the regulation of the vascular tone, actually, tissue vascularization.

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4

Adrian, Gerild, Edi Suryanto, and Defny S. Wewengkang. "AKTIVITAS PENANGKAL RADIKAL BEBAS DARI FRAKSI KULIT KAYU SAGU BARUK (Arenga microcarpha Beccari)." PHARMACON 10, no. 1 (February 24, 2021): 762. http://dx.doi.org/10.35799/pha.10.2021.32777.

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ABSTRACTThis study aims to determine the antioxidant activity and free radical antidote from fraction of bark sago baruk (Arenga microcarpha Beccari). This study initiated by extracting the powder of bark sago baruk using the maceration method for 3 days with ethanol 80%. The extract then partitioned using a series of solvent such as petroleum ether, ethyl acetate, buthanol, aquadest. The results showed that the ethyl acetate fraction had the highest free radical antidote content followed by the aquadest fraction, buthanol fraction, petroleum ether fraction. The content of free radical antidote respectively was 86,25%; 66,30%; 65,32%; 43,43%. Based on this study, the ethyl acetate fraction was the best fraction can act as an antidote to free radicals better than other fractions. Keywords: Bark sago baruk, fraction, free radical antidote ABSTRAKPenelitian ini bertujuan untuk menentukan Aktivitas penangkal radikal bebas dari fraksi kulit kayu sagu baruk (Arenga microcarpha beccari). Penelitian ini dimulai dengan mengekstraksi serbuk kulit kayu sagu baruk menggunakan cara maserasi selama 3 hari dengan pelarut etanol 80%. Ekstrak kemudian dipartisi menggunakan pelarut petroleum eter, etil asetat, butanol, dan aquades. kemudian ditentukan aktivitas antioksidan dan penangkal radikal bebas. Hasilnya menunujukan bahwa fraksi etil asetat memiliki kandungan penangkal radikal bebas tertinggi diikuti fraksi aquades, fraksi butanol, dan fraksi petroleum eter. Kandungan penangkal radikal bebas berturut-turut adalah 86,25%; 66,30%; 65,32%; 43,43%. Berdasarkan penelitian ini, dapat disimpulkan bahwa fraksi etil asetat dapat berperan sebagai penangkal radikal bebas lebih baik dibandingkan dengan fraksi lainnya. Kata Kunci: Kulit Kayu Sagu Baruk, Fraksi, Penangkal Radikal Bebas

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5

Silaev, Michael M. "Free-Radical Nonbranched-Chain Oxidation of Hydrogen." International Journal of Innovative Research in Computer Science & Technology 6, no. 5 (September 2018): 91–98. http://dx.doi.org/10.21276/ijircst.2018.6.5.1.

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6

Mikayil Aliyev, Mirza, Ulduz Yunis Safarova, and Shafiqa Jahangir Jafarova. "CHARACTERISTICS AND THERAPEUTIC EFFECTS OF THE NOVEL FREE RADICAL SCAVENGER – EDARAVONE." NATURE AND SCIENCE 04, no. 05 (December 28, 2020): 17–20. http://dx.doi.org/10.36719/2707-1146/05/17-20.

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Edaravone is the first free radical scavenger which approved clinically and has an ability to decrease the level of free radicals in cells. Edaravone is a strong antioxidant, which can protect different cells (e.g. endothelial cells) against damage by ROS by inhibiting the lipoxygenase metabolism of arachidonic acid, by trapping hydroxyl radicals, by increasing prostacyclin production, by inhibiting alloxan-induced lipid peroxidation, etc. Because of that, Edaravone is used in treatment of diseases which are associated with oxidative stress. Key words: edaravone, free radical, antioxidant, neuroprotective agent, oxidative stress

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7

Horgan, John. "Free Radical." Scientific American 262, no. 5 (May 1990): 40–44. http://dx.doi.org/10.1038/scientificamerican0590-40.

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Silaev, Michael M. "KINETIC EQUATIONS FOR RADICAL-CHAIN OXIDATION INVOLVING PROCESS-INHIBITING ALKYL (OR HYDRO)TETRAOXYL FREE RADICAL." American Journal of Applied Sciences 05, no. 06 (June 30, 2023): 29–48. http://dx.doi.org/10.37547/tajas/volume05issue06-07.

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The derivation of kinetic equations for the oxidation processes by the free-radical nonbranched-chain mechanism is shown. This derivation is based on the proposed reaction scheme for the initiated addition of free radicals to the multiple bond of the molecular oxygen includes the addition reaction of the peroxyl free radical to the oxygen molecule to form the tetraoxyl free radical. This reaction competes with chain propagation reactions through a reactive free radical. The chain evolution stage in this scheme involves a few of free radicals, one of which – alkyl(or hydro)tetraoxyl – is relatively low-reactive and inhibits the chain process by shortening of the kinetic chain length. The rate equations (containing one to three parameters to be determined directly) are deduced using the quasi-steady-state treatment. These kinetic equations were used to describe the γ-induced nonbranched-chain processes of free-radical oxidation of liquid o-xylene at 373 K and hydrogen dissolved in water containing various amounts of oxygen at 296 K. The ratios of rate constants of competing reactions and rate constants of addition reactions to the molecular oxygen are defined. In these processes the oxygen with the increase of its concentration begins to act as an oxidation autoinhibitor (or an antioxidant), and the rate of peroxide formation as a function of the dissolved oxygen concentration has a maximum. It is shown that a maximum in these curves arises from the competition between hydrocarbon (or hydrogen) molecules and dioxygen for reacting with the emerging peroxyl 1:1 adduct radical. From the energetic standpoint possible nonchain pathways of the free-radical oxidation of hydrogen and the routes of ozone decay via the reaction with the hydroxyl free radical in the upper atmosphere (including the addition yielding the hydrotetraoxyl free radical, which can be an intermediate in the sequence of conversions of biologically hazardous UV radiation energy) were examined. The energetics of the key radical-molecule gas-phase reactions is considered.

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9

Livi Kharisma Wibawa, Vinda Maharani Patricia, and Livia Syafnir. "Aktivitas Antioksidan pada Tanaman Mengkudu (Morinda citrifolia L.)." Bandung Conference Series: Pharmacy 4, no. 2 (August 12, 2024): 313–20. http://dx.doi.org/10.29313/bcsp.v4i2.13911.

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Abstract. Degenerative diseases are caused by highly reactive free radicals. This free radical activity can be inhibited by antioxidant compounds. Antioxidants are substances necessary for the body to neutralize free radicals, compensating for the lack of electrons in free radicals, inhibiting the chain reaction of free radical formation, and preventing free radicals from damaging normal cells. The noni plant (Morinda citrifolia L.) has the potential to exert antioxidant effects by reducing the concentration of free radicals in the body and contains many flavonoids that may be useful as antioxidants. The research aims to determine the potential antioxidant activity of the noni plant (Morinda citrifolia L.) and its active compounds. The research method used is a systematic literature review (SLR). The results of this study showed that the tested parts of the Noni plant were the fruits, seeds, leaves and bark, which had the potential to have antioxidant activity using the DPPH, FRAP and ABTS antioxidant test methods. Through the DPPH testing method, the parts of the plant that have the strong activity for the best antioxidant can be found in the fruit. Abstrak. Penyakit degeneratif disebabkan oleh radikal bebas yang sangat reaktif. Aktivitas radikal bebas ini dapat dihambat oleh senyawa antioksidan. Antioksidan adalah zat yang diperlukan oleh tubuh untuk menetralisir radikal bebas dengan mengisi kembali kekurangan elektron pada radikal bebas, menghambat reaksi berantai pembentukan radikal bebas, dan mencegah kerusakan sel normal akibat radikal bebas. Tanaman mengkudu (Morinda citrifolia L.) berpotensi menunjukkan aktivitas antioksidan dengan menurunkan konsentrasi radikal bebas pada tubuh, dan banyak mengandung flavonoid yang dapat bermanfaat sebagai zat antioksidan. Penelitian ini bertujuan untuk mengetahui potensi aktivitas antoksidan pada tanaman mengkudu (Morinda citrifolia L.), serta mengetahui senyawa aktifnya. Metode penelitian yang digunakan adalah Systematic Literature Review (SLR). Hasil penelitian ini diperoleh bagian tanaman mengkudu yang sudah diteliti yaitu buah, biji, daun dan kulit yang berpotensi memiliki aktivitas antioksidan dengan menggunakan metode pengujian antioksidan DPPH, FRAP dan ABTS. Dari bagian tanaman tersebut, yang paling berpotensi memiliki aktivitas antioksidan paling kuat terdapat pada bagian buah dengan menggunakan metode pengujian DPPH.

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Zhao, Zizhen, Chen Fu, Yuping Zhang, and Ailing Fu. "Dimeric Histidine as a Novel Free Radical Scavenger Alleviates Non-Alcoholic Liver Injury." Antioxidants 10, no. 10 (September 27, 2021): 1529. http://dx.doi.org/10.3390/antiox10101529.

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Non-alcoholic liver injury (NLI) is a common disease worldwide. Since free radical damage in the liver is a crucial initiator leading to diseases, scavenging excess free radicals has become an essential therapeutic strategy. To enhance the antioxidant capacity of histidine, we synthesized a protonated dimeric histidine, H-bihistidine, and investigated its anti-free radical potential in several free-radical-induced NLI. Results showed that H-bihistidine could strongly scavenge free radicals caused by H2O2, fatty acid, and CCl4, respectively, and recover cell viability in cultured hepatocytes. In the animal model of nonalcoholic fatty liver injury caused by high-fat diet, H-bihistidine reduced the contents of transaminases and lipids in serum, eliminated the liver’s fat accumulation, and decreased the oxidative damage. Moreover, H-bihistidine could rescue CCl4-induced liver injury and recover energy supply through scavenging free radicals. Moreover, liver fibrosis prepared by high-fat diet and CCl4 administration was significantly alleviated after H-bihistidine treatment. This study suggests a novel nonenzymatic free radical scavenger against NLI and, potentially, other free-radical-induced diseases.

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Dissertations / Theses on the topic "Free radical"

1

Barreto, Joao Pedro Cabaco Moniz. "Dioxygen free radical reactions." Thesis, Oxford Brookes University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389105.

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Euapermkiati, Anucha. "Free radical telomerisation reactions." Thesis, University of Bradford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278895.

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Shooter, Andrew James. "Living free radical polymerisation." Thesis, University of Warwick, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263817.

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4

Wood, Geoffrey Paul Farra. "Theoretical Investigations of Radical-Mediated Protein Oxidation." Thesis, The University of Sydney, 2006. http://hdl.handle.net/2123/1413.

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This thesis primarily details the application of high-level ab initio quantum chemistry techniques in order to understand aspects of free-radical mediated protein oxidation. Traditionally, product analysis and electron paramagnetic resonance (EPR) spectroscopy are the primary means for elucidating the chemistry of protein oxidation. However, in experiments involving relatively small proteins reacting with a controlled radical-flux, a vast array of compounds can be produced, which are often difficult to analyse. Quantum chemical techniques on the other hand, can calculate the properties of any particular species directly, without suffering from the problems associated with experiment, such as side-reactions and chain processes. The results presented in this thesis are aimed at elucidating mechanistic details of protein oxidation, which might otherwise be difficult to probe experimentally. Chapter 1 gives an overview of the free-radical hypothesis of disease and ageing. Protein-derived radicals can undergo a variety of reactions, with the particular reaction that occurs depending on numerous aspects. Many types of reactions have been identified through radiolysis experiments of amino acids, and these are detailed in this chapter. In addition, the key reactive species are characterized and their different chemistries explained. Chapter 2 details the theoretical tools used throughout this thesis. Species with unpaired electrons (radicals) present unique problems for quantum chemistry to handle, thus an appropriate choice of theoretical technique is needed. The approach taken in this thesis is to use high-level compound methods, many of which have been directly formulated to give improved results for radical species, to provide benchmark quality results by which other less demanding techniques can be assessed. During the course of this study, it became apparent there was a void in the armoury of tools that could be used for the theoretical chemistry calculations. Chapter 3 details the formulation of a new tool in an attempt to fill this gap. Historically, the formulation of this new procedure came after much of the work in this thesis had been carried out. Thus, for the study of many of the reactions of this thesis the new method has not been used. However, it is most appropriate to place its formulation after summarizing the current status of techniques in common use today. Chapters 4 and 5 detail computations carried out on models of peptides containing backbone carbon- and nitrogen-centered radicals. A number of different theoretical techniques are used in these chapters, ranging from the highly accurate and computationally intensive to the less reliable and less demanding. The highly accurate techniques are used to gauge the accuracy of the other less demanding theoretical techniques so that the latter can be used with confidence in larger systems. Not only is the choice of theoretical technique important but also the judicious choice of model is essential. With this in mind, models are incrementally built until convergence of the particular property of interest is reached. Chapters 6 and 7 detail the calculations of Î²-scission reactions of alkoxyl radicals, which are a particular class of reaction known to occur on peptide backbones. Alkoxyl radicals are particularly difficult for theory to describe correctly. Therefore, Chapter 6 extensively assesses and then identifies the theoretical methods needed to portray them. Chapter 7 uses the techniques identified in the previous chapter in order to predict how the preference for a particular type of Î²-scission reaction changes.

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Wood, Geoffrey Paul Farra. "Theoretical Investigations of Radical-Mediated Protein Oxidation." University of Sydney, 2006. http://hdl.handle.net/2123/1413.

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Doctor of Philosophy (PhD)<br>This thesis primarily details the application of high-level ab initio quantum chemistry techniques in order to understand aspects of free-radical mediated protein oxidation. Traditionally, product analysis and electron paramagnetic resonance (EPR) spectroscopy are the primary means for elucidating the chemistry of protein oxidation. However, in experiments involving relatively small proteins reacting with a controlled radical-flux, a vast array of compounds can be produced, which are often difficult to analyse. Quantum chemical techniques on the other hand, can calculate the properties of any particular species directly, without suffering from the problems associated with experiment, such as side-reactions and chain processes. The results presented in this thesis are aimed at elucidating mechanistic details of protein oxidation, which might otherwise be difficult to probe experimentally. Chapter 1 gives an overview of the free-radical hypothesis of disease and ageing. Protein-derived radicals can undergo a variety of reactions, with the particular reaction that occurs depending on numerous aspects. Many types of reactions have been identified through radiolysis experiments of amino acids, and these are detailed in this chapter. In addition, the key reactive species are characterized and their different chemistries explained. Chapter 2 details the theoretical tools used throughout this thesis. Species with unpaired electrons (radicals) present unique problems for quantum chemistry to handle, thus an appropriate choice of theoretical technique is needed. The approach taken in this thesis is to use high-level compound methods, many of which have been directly formulated to give improved results for radical species, to provide benchmark quality results by which other less demanding techniques can be assessed. During the course of this study, it became apparent there was a void in the armoury of tools that could be used for the theoretical chemistry calculations. Chapter 3 details the formulation of a new tool in an attempt to fill this gap. Historically, the formulation of this new procedure came after much of the work in this thesis had been carried out. Thus, for the study of many of the reactions of this thesis the new method has not been used. However, it is most appropriate to place its formulation after summarizing the current status of techniques in common use today. Chapters 4 and 5 detail computations carried out on models of peptides containing backbone carbon- and nitrogen-centered radicals. A number of different theoretical techniques are used in these chapters, ranging from the highly accurate and computationally intensive to the less reliable and less demanding. The highly accurate techniques are used to gauge the accuracy of the other less demanding theoretical techniques so that the latter can be used with confidence in larger systems. Not only is the choice of theoretical technique important but also the judicious choice of model is essential. With this in mind, models are incrementally built until convergence of the particular property of interest is reached. Chapters 6 and 7 detail the calculations of Î²-scission reactions of alkoxyl radicals, which are a particular class of reaction known to occur on peptide backbones. Alkoxyl radicals are particularly difficult for theory to describe correctly. Therefore, Chapter 6 extensively assesses and then identifies the theoretical methods needed to portray them. Chapter 7 uses the techniques identified in the previous chapter in order to predict how the preference for a particular type of Î²-scission reaction changes.

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Grice, I. Darren, and n/a. "Some New Aspects of Radical Trapping Using an Aminoxyl Radical Trap." Griffith University. School of Science, 1993. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20050915.150556.

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An investigation of the initiation mechanism in the free radical copolymerisation of acrylonitrile and vinyl acetate using the aminoxyl radical trapping technique, employing 1,1 ,3,3-tetramethyl-2,3-dihydro- 1 Hisoindol-2-yloxyl is reported. Based upon the experimental results, the mechanism of initiation is suggested as proceeding via the 'free monomer' mechanism. Additionally, the effect of Lewis acids on the initiation mechanism is reported. A study of the addition of phosphorus-centred radicals to alkenes and phenylacetylene, utilising the aminoxyl radical trapping technique is reported. The results indicate a decreased rate of addition by both diphenylphosphinyl and dimethoxyphosphinyl radicals to cyclic versus acyclic alkenes. In contrast to cyclic alkenes, both these phosphorus-centred radicals add readily to the triple bond of phenylacetylene. The stereochemistry of the addition of diphenyiphosphinyl and dimethoxyphosphinyl radicals and of the aminoxyl trap is discussed. The stereochemistry of the addition of benzoyloxyl radicals to a conformationally rigid alkene, trans-a2-octalin is reported. Attempts to examine the initiation mechanism in the free radical copolymerisation of styrene/maleic anhydride and of styrene/tetracyanoethylene utilising the aminoxyl radical trapping technique are described. Also described are attempts to synthesise some new phosphorus radical initiators.

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7

Grice, I. Darren. "Some New Aspects of Radical Trapping Using an Aminoxyl Radical Trap." Thesis, Griffith University, 1993. http://hdl.handle.net/10072/365216.

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An investigation of the initiation mechanism in the free radical copolymerisation of acrylonitrile and vinyl acetate using the aminoxyl radical trapping technique, employing 1,1 ,3,3-tetramethyl-2,3-dihydro- 1 Hisoindol-2-yloxyl is reported. Based upon the experimental results, the mechanism of initiation is suggested as proceeding via the 'free monomer' mechanism. Additionally, the effect of Lewis acids on the initiation mechanism is reported. A study of the addition of phosphorus-centred radicals to alkenes and phenylacetylene, utilising the aminoxyl radical trapping technique is reported. The results indicate a decreased rate of addition by both diphenylphosphinyl and dimethoxyphosphinyl radicals to cyclic versus acyclic alkenes. In contrast to cyclic alkenes, both these phosphorus-centred radicals add readily to the triple bond of phenylacetylene. The stereochemistry of the addition of diphenyiphosphinyl and dimethoxyphosphinyl radicals and of the aminoxyl trap is discussed. The stereochemistry of the addition of benzoyloxyl radicals to a conformationally rigid alkene, trans-a2-octalin is reported. Attempts to examine the initiation mechanism in the free radical copolymerisation of styrene/maleic anhydride and of styrene/tetracyanoethylene utilising the aminoxyl radical trapping technique are described. Also described are attempts to synthesise some new phosphorus radical initiators.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Science<br>Science, Environment, Engineering and Technology<br>Full Text

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8

Johansson, Erik. "Free radical mediated cellulose degradation." Doctoral thesis, KTH, Chemistry, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3477.

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<p>This thesis addresses the mechanisms involved in cellulosedegradation in general and Totally Chlorine Free (TCF) bleachingof pulp in particular. The thesis shows that the cellulosedegradation during high consistency ozone bleaching is explainedby free radical chain reactions.</p><p>By simulation, it has been shown that the number, weight andviscosity average of liner polymer chain length can be used tocalculate the number of random scissions in a linear polymer ofany molecular weight distribution, provided that there is acalibrated Mark-Houwink equation. A model describing partialdegradation of molecular weight distributions of linear polymersmeasured with viscometry was developed and verifiedexperimentally. The model predicts viscometric measurement ofchemical cellulose degradation by a rapidly reacting reagent tobe strongly dependent on cellulose accessibility.</p><p>The role of free radical reactions in cellulose degradationwas studied by varying the amount of ferrous ions and ozone addedto the cotton linters. The result was compared to the resultsobtained from cellulose of lower crystallinity (cellulose beads)by measuring average chain length. When a ferryl ion reacted withcotton linters in the presence of ozone, the very formation ofone glycosidic radical was more significant to degradation thanthe final step of forming one oxidised glycoside. The inefficientdegradation observed of the oxidation step is explainable by theamount of accessible glycosides being too small to influenceviscometry. The efficient degradation observed in associationwith the glycosidic radical formation is explained by initiationof free radical chain reactions that are propagated as long asthere is ozone in the system. As none of these phenomena werefound in the less crystalline cellulose, cellulose structureappears to be important for how free radical mediated cellulosedegradation develops.</p><p>The theory of free radical chain reactions coupled withdiffusion suggests a concentric expansion of the chain reactionsoutwards from the initial site of radical formation duringozonation of carbohydrates. This was confirmed by demonstratingfree radical chain reactions spreading from a spot of initiationoutwards during ozonation of a filter paper, using a pH-indicatorto monitor acid formation. Furthermore, the interior and exteriorof cellulose fibres doped with initiator were shown to bepermeated by small holes after ozonation.</p><p>Ethylene glycol was shown to improve the selectivity duringozone bleaching of oxygen bleached kraft pulp at pH 3. Optimalconditions were obtained at pH 3 for 25 wt% ethylene glycol. Theinfluence of ethylene glycol on selectivity is explained by aproportion of the free radical chain reactions being carried bythe ethylene glycol instead of the cellulose during ozonebleaching. The observations were summarised in the form of amodel where the observed degradations for pulp, bleached pulp andcotton fibres during both ozone bleaching and ethylene glycolassisted ozone bleaching were shown to agree with each other.</p><p>From g-irradiation of ozonised aqueous solutions of alcohol,the rate constant of superoxide formation from the peroxylradical of methanol was estimated to be 10 s<sup>-1</sup>. Rate constants of the reactions between ozone andalkylperoxyl radicals were determined to be around 10<sup>4</sup>M<sup>-1</sup>s<sup>-1</sup>. The possibility of the reaction betweenalkylperoxyl radicals and ozone contributing significantly tofree radical chain reactions during ozonation of carbohydratesand alcohols could therefore be ruled out.</p><p>Cellulose, degradation, free radical, ozone, selectivity,ethylene glycol, alcohol, bleaching, kraft pulp, cotton linters,delignification, fibre, fibril, crystallinity, ferryl ion, freeradical chain reactions, TCF, viscometry, molecular weightdistributions, random scissions.</p>

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9

Hancock-Chen, Tanya. "Biologically relevant free radical reactions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0019/NQ58282.pdf.

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Johansson, Erik E. "Free radical mediated cellulose degradation /." Stockholm : Department of Chemistry, Nuclear Chemistry, Royal Institute of Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3477.

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Books on the topic "Free radical"

1

Coupé, Nez. Free radical. Fayetteville, NC: Croomia Books, 1992.

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Murphy, Claire Rudolf. Free radical. New York: Clarion Books, 2002.

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Myette, Michael. Free radical. Pittsburgh, PA: Pemberton Mysteries, 2008.

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Paulauskas, Irena O. Radical polymerization: New developments. Hauppauge, N.Y: Nova Science Publishers, 2011.

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Fehér, J. Free radical reactions in medicine. Berlin: Springer-Verlag, 1987.

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Perkins, M. John. Radical chemistry. New York: Ellis Horwood, 1994.

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Derek, Barton. Half a century of free radical chemistry. Cambridge [England]: Cambridge University Press, 1993.

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Bruce, Wallace Kendall, ed. Free radical toxicology. Washington, DC: Taylor & Francis, 1997.

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9

Postigo, J. Alberto. Organic radical reactions in water and alternative media. Hauppauge, N.Y: Nova Science Publishers, 2011.

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Forbes, Malcolm D. E., ed. Carbon-Centered Free Radicals and Radical Cations. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2009. http://dx.doi.org/10.1002/9780470584118.

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Book chapters on the topic "Free radical"

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Gooch, Jan W. "Free Radical." In Encyclopedic Dictionary of Polymers, 325–26. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_5286.

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Punekar, Narayan S. "Free Radicals and Radical Enzymology." In ENZYMES: Catalysis, Kinetics and Mechanisms, 451–60. Singapore: Springer Nature Singapore, 2025. https://doi.org/10.1007/978-981-97-8179-9_34.

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Drăguţan, I., A. Caragheorgheopol, H. Căldăraru, and R. J. Mehlhorn. "Hydrophobic Radical-Ions." In Organic Free Radicals, 47–48. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-73963-7_24.

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Hayashi, Nariyuki, and Dalton W. Dietrich. "Free Radical Production." In Brain Hypothermia Treatment, 24. Tokyo: Springer Japan, 2004. http://dx.doi.org/10.1007/978-4-431-53953-7_14.

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Norman, Richard, and James M. Coxon. "Free-radical reactions." In Principles of Organic Synthesis, 523–60. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-2166-8_17.

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Serra, Christophe. "Free Radical Polymerization." In Micro Process Engineering, 197–212. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2013. http://dx.doi.org/10.1002/9783527631445.ch29.

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Grossman, Robert B. "Free-Radical Reactions." In The Art of Writing Reasonable Organic Reaction Mechanisms, 212–55. New York, NY: Springer New York, 1999. http://dx.doi.org/10.1007/978-1-4757-3030-2_5.

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Grossman, Robert B. "Free-Radical Reactions." In The Art of Writing Reasonable Organic Reaction Mechanisms, 283–339. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-28733-7_5.

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Carey, Francis A., and Richard J. Sundberg. "Free-Radical Reactions." In Advanced Organic Chemistry, 651–727. Boston, MA: Springer US, 1990. http://dx.doi.org/10.1007/978-1-4613-9795-3_12.

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Hess, John L. "Free radical scavenging." In Plant Responses to the Gaseous Environment, 99–120. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1294-9_6.

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Conference papers on the topic "Free radical"

1

Dunlop, A. K. "Catalysis and Inhibition in Oxygen Scavenging." In CORROSION 1986, 1–11. NACE International, 1986. https://doi.org/10.5006/c1986-86176.

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Abstract The catalysis of oxygen scavenging reactions can be placed in two categories, 1) those depending on a free radical chain mechanism and 2) those in which a catalytic intermediate redox cycle is involved. Sulfite scavenging exemplifies the first category as the free radical chain mechanism is the only one effective in this system. This mechanism makes the sulfite system susceptible to a great variety of inhibiting effects. However, mechanistic understanding is available to solve such problems. Hydrazine can provide examples in each category. Catalysis via the hydroquinone/quinone cycle exemplifies the intermediate redox approach and, at high temperature, hydrazine appears to cleave rapidly enough to provide its own free radical chain initiation.

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Lewandowski, Heather J., L. Paul Parazzoli, and Daniel Lobser. "Cold Free-Radical NH Molecules." In Laser Science. Washington, D.C.: OSA, 2006. http://dx.doi.org/10.1364/ls.2006.ltuh1.

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Leahy, David J., Douglas R. Cyr, David L. Osborn, and Daniel M. Neumark. "Fast-beam studies of free-radical photodissociation: the CH2NO2 radical." In OE/LASE'93: Optics, Electro-Optics, & Laser Applications in Science& Engineering, edited by Cheuk Yiu Ng. SPIE, 1993. http://dx.doi.org/10.1117/12.143115.

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Scott, T. W., and S. N. Liu. "Picosecond cage recombination measurements of polyatomic free radical pairs." In International Laser Science Conference. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/ils.1986.thl51.

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Geminate free radical recombination is an important testing ground for current theories of chemical reaction dynamics in liquids. The work described here deals with the recombination of phenyl thiyl radicals in liquid hydrocarbons. Photolysis of diphenyl disulfides using near-ultraviolet light generates thiyl radicals which are detected by picosecond transient absorption spectroscopy. We find that the rate and extent of cage recombination is controlled by solvent viscosity and by the dipole-dipole reorientation energy of a polar radical pair. In moderately viscous liquids such as decalin, for example, cage recombination occurs with a 50% yield and with a half-life of ~150 ps. The influence of both temperature and solvent composition on recombination can be explained by a simple hydrodynamic model of diffusion controlled reactions, using a radiation boundary condition that mimics the reorientation barrier. In polar liquids, cage escape is enhanced by solvation of the radical pair. Based on the interpretation of these experiments it appears that the use of chemical substituents to alter the dipole movement of the radical can be used to study the recombination dynamics in more detail.

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Pfaendtner, Jim, Linda J. Broadbelt, and Q. Jane Wang. "Quantum Chemical Studies of Free-Radical, Hindered Phenol Stabilizers." In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-64007.

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Quantum chemical investigations of the action of hindered phenol radical stabilizers in lubricant degradation chemistry have been completed. We are currently developing the first mechanistic models of lubricant degradation with the aim of including the chemistry of additives such as radical stabilizers that are found in commercial lubricant formulations. A key component of development of these models is obtaining reliable estimates of the kinetic parameters for all reactions. Specifically, rate constants and structure-reactivity correlations for the interaction of hindered phenol radical stabilizers with small peroxy radicals have been sought using quantum chemistry and transition state theory. Accurate thermodynamic properties of hindered phenol radical stabilizers and structure-reactivity relationships have been obtained. Such relationships provide researchers the ability to quickly estimate reactivity of hindered phenol stabilizers using their thermodynamic properties and therefore may be useful in additive design.

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Bochinski, J. R., E. R. Hudson, and J. Ye. "Stark manipulation of the free radical OH." In Quantum Electronics and Laser Science (QELS). Postconference Digest. IEEE, 2003. http://dx.doi.org/10.1109/qels.2003.238172.

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Chen, H., Y. T. Chan, H. V. Poor, and K. Sezaki. "Range-Free Localization with the Radical Line." In ICC 2010 - 2010 IEEE International Conference on Communications. IEEE, 2010. http://dx.doi.org/10.1109/icc.2010.5502304.

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Lulan, Theodore Y. K., Sri Fatmawati, Mardi Santoso, and Taslim Ersam. "Free radical scavenging activity of Artocarpus champeden extracts." In THE 3RD INTERNATIONAL SEMINAR ON CHEMISTRY: Green Chemistry and its Role for Sustainability. Author(s), 2018. http://dx.doi.org/10.1063/1.5082460.

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Girbu, Vladilena, Nicon Ungur, Philippe Renaud, and Veaceslav Kulcitki. "Free radical functionalizations of labdanes and related diterpenoids." In New frontiers in natural product chemistry, scientific seminar with international participation. Institute of Chemistry, 2021. http://dx.doi.org/10.19261/nfnpc.2021.ab20.

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Hudson, Eric, J. R. Bochinski, H. J. Lewandowski, and Jun Ye. "Cold free radical molecules in the laboratory frame." In International Quantum Electronics Conference. Washington, D.C.: OSA, 2004. http://dx.doi.org/10.1364/iqec.2004.imi5.

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Reports on the topic "Free radical"

1

Dagdigian, Paul J. Spectroscopic Characterization of Free Radical Intermediates. Fort Belvoir, VA: Defense Technical Information Center, May 2001. http://dx.doi.org/10.21236/ada394529.

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Wang, M., J. M. Smith, and B. J. McCoy. Free-radical kinetics of coal liquefaction. Office of Scientific and Technical Information (OSTI), July 1994. http://dx.doi.org/10.2172/26601.

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Cyr, Douglas Robert. Fast beam studies of free radical photodissociation. Office of Scientific and Technical Information (OSTI), November 1993. http://dx.doi.org/10.2172/10148491.

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Osborn, David Lewis. Photodissociation dynamics and spectroscopy of free radical combustion intermediates. Office of Scientific and Technical Information (OSTI), December 1996. http://dx.doi.org/10.2172/503521.

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Miller, Roger E. The Growth and Characterization of Metastable Free Radical Nanoclusters. Fort Belvoir, VA: Defense Technical Information Center, June 2004. http://dx.doi.org/10.21236/ada424162.

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Baer, Tomas, and Roger E. Miller. The Growth and Characterization of Metastable Free Radical Nanoclusters. Fort Belvoir, VA: Defense Technical Information Center, January 2007. http://dx.doi.org/10.21236/ada469731.

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Brennecke, Joan F. Studies of Ionic and Free Radical Reactions in Supercritical Water. Fort Belvoir, VA: Defense Technical Information Center, September 2001. http://dx.doi.org/10.21236/ada396304.

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Jacox, Marilyn E. Free Radical Detection and Reactions in the Decomposition of Energetic Materials. Fort Belvoir, VA: Defense Technical Information Center, July 1987. http://dx.doi.org/10.21236/ada184677.

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Curl, R. F., and G. P. Glass. Infrared absorption spectroscopy and chemical kinetics of free radicals. [HCCN; CCH-H[sub 2] reaction; propargyl radical recombination]. Office of Scientific and Technical Information (OSTI), April 1993. http://dx.doi.org/10.2172/6566601.

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Lampe, F. W. The free-radical and ion chemistry of volatile silanes, germanes and phosphines. Office of Scientific and Technical Information (OSTI), January 1990. http://dx.doi.org/10.2172/6290400.

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