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Journal articles on the topic 'Free radical reactions'

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Author: Grafiati

Published: 4 June 2021

Last updated: 2 March 2023

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1

Jonsson, M., J. Lind, T. Reitberger, T. E. Eriksen, and G. Merenyi. "Free radical combination reactions involving phenoxyl radicals." Journal of Physical Chemistry 97, no. 31 (August 1993): 8229–33. http://dx.doi.org/10.1021/j100133a018.

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2

Khalid, Maher, and Shireen Mohammed. "Recent Free-Radical Reactions." Asian Journal of Chemistry 31, no. 1 (2018): 25–40. http://dx.doi.org/10.14233/ajchem.2019.21635.

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3

Sibi, Mukund P., and Ned A. Porter. "Enantioselective Free Radical Reactions." Accounts of Chemical Research 32, no. 2 (February 1999): 163–71. http://dx.doi.org/10.1021/ar9600547.

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4

Mohammad, Mahboob, Muhammad Tariq, and Muhammad Tahir Soomro. "“Long-life” atom-free radical: Generation and reactions of bromine atom-free radical." Collection of Czechoslovak Chemical Communications 75, no. 11 (2010): 1061–74. http://dx.doi.org/10.1135/cccc2010066.

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In order to study the damaging or beneficial properties of bromine atom-free radical, reaction of the free radical (Br•) with some biologically important compounds were investigated. Br• was generated through electrochemical oxidation of bromide ion (Br–). First the reactivity of Br• atom-free radical vis a vis its dimerization to form Br2, was studied using cyclic voltammetry and spectroelectrochemistry. Through these techniques it was ascertained that the substrates understudy and the under experimental conditions used, underwent reactions with Br• and not with dibromine (Br2). The monitoring of the reactions of Br• with glycine and cytosine led us to conclude that whereas cytosine reacted with Br• as simple chemical reaction (EC mechanism), glycine underwent a catalytic reaction (EC′ mechanism).

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5

Silaev, Michael M. "OXYGEN AS OXIDANT AND ANTIOXIDANT." EPH - International Journal of Applied Science 1, no. 2 (June 27, 2015): 21–32. http://dx.doi.org/10.53555/eijas.v1i2.3.

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New reaction scheme is suggested for the initiated nonbranched-chain addition of free radicals to the multiple bond of the molecular oxygen. The scheme 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 (tetraoxyl) is relatively low-reactive and inhibits the chain process by shortening of the kinetic chain length. Based on the proposed scheme rate equations (containing one to three parameters to be determined directly) are deduced using quasi-steady-state treatment. The kinetic description with use the obtained rate equations is applied to the γ-induced nonbranched-chain processes of the freeradical oxidation of liquid o-xylene at 373 K and hydrogen dissolved in water containing different 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 autoingibitor (or an antioxidant), and the rate of peroxide formation as a function of the dissolved oxygen concentration has a maximum. 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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6

Harasym, N. P., M. Y. Booklyv, A. R. Zyn, S. M. Mandzynets, A. O. Bezkorovainy, and D. I. Sanahursky. "Quercetin and histamine effects on free radical reactions in rat erythrocytes." Ukrainian Biochemical Journal 93, no. 1 (February 22, 2021): 96–103. http://dx.doi.org/10.15407/ubj93.01.096.

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7

Goodman, B. A. "The involvement of oxygen-derived free radicals in plant–pathogen interactions." Proceedings of the Royal Society of Edinburgh. Section B. Biological Sciences 102 (1994): 479–93. http://dx.doi.org/10.1017/s0269727000014500.

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SynopsisPlants have evolved a multiplicity of defence mechanisms against pathogen attack. Their modes of action may be to (i) kill the pathogen directly, (ii) block the action of enzymes required for infection, or (iii) erect barriers to pathogen growth. Some of these reactions proceed via free radical intermediates and make use of either atmospheric oxygen or reactive oxygen species. This paper reviews the various types of reaction involving oxygen-derived free radicals that are initiated in plant tissue when it is invaded by pathogenic organisms. Both the production of free radicals by plants in defensive processes and the utilisation of free radicals by pathogens in offensive reactions are considered and particular attention is given to the use of electron paramagnetic resonance (EPR) spectroscopy for the direct observation of such free radical reactions.

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8

Davies, M. J., S. Fu, and R. T. Dean. "Protein hydroperoxides can give rise to reactive free radicals." Biochemical Journal 305, no. 2 (January 15, 1995): 643–49. http://dx.doi.org/10.1042/bj3050643.

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Proteins damaged by free-radical-generating systems in the presence of oxygen yield relatively long-lived protein hydroperoxides. These hydroperoxides have been shown by e.p.r. spectroscopy to be readily degraded to reactive free radicals on reaction with iron(II) complexes. Comparison of the observed spectra with those obtained with free amino acid hydroperoxides had allowed identification of some of the protein-derived radical species (including a number of carbon-centred radicals, alkoxyl radicals and a species believed to be the CO2 radical anion) and the elucidation of novel fragmentation and rearrangement processes involving amino acid side chains. In particular, degradation of hydroperoxide functions on the side chain of glutamic acid is shown to result in decarboxylation at the side-chain carboxy group via the formation of the CO2 radical anion; the generation of an identical radical from hydroperoxide groups on proteins suggests that a similar process occurs with these molecules. In a number of cases these fragmentation and rearrangement reactions give rise to further reactive free radicals (R., O2-./HO2., CO2-.) which may act as chain-carrying species in protein oxidations. These studies suggest that protein hydroperoxides are capable of initiating further radical chain reactions both intra- and inter-molecularly, and provide information on some of the fundamental mechanisms of protein alteration and side-chain fragmentation.

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9

Crich, David, and John W. Davies. "Stereoselectivity in free radical reactions." Tetrahedron Letters 28, no. 36 (1987): 4205–8. http://dx.doi.org/10.1016/s0040-4039(00)95580-1.

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10

Barluenga, Jose, and Miguel Yus. "Free radical reactions of organomercurials." Chemical Reviews 88, no. 3 (May 1988): 487–509. http://dx.doi.org/10.1021/cr00085a003.

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11

Goodman, Bernard A., Sheila M. Glidewell, Nigel Deighton, and Ann E. Morrice. "Free radical reactions involving coffee." Food Chemistry 51, no. 4 (January 1994): 399–403. http://dx.doi.org/10.1016/0308-8146(94)90192-9.

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12

Meier, B. "Free radical reactions in medicine." Toxicon 28, no. 10 (January 1990): 1244. http://dx.doi.org/10.1016/0041-0101(90)90133-r.

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13

Mahe, Capucine, and Kevin Cariou. "Ynamides in Free Radical Reactions." Advanced Synthesis & Catalysis 362, no. 22 (October 9, 2020): 4820–32. http://dx.doi.org/10.1002/adsc.202000849.

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14

WALLING, C. "ChemInform Abstract: Free Radical Reactions." ChemInform 28, no. 12 (August 4, 2010): no. http://dx.doi.org/10.1002/chin.199712314.

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15

Murphy, John A. "Free radicals in synthesis. Clean reagents affording oxidative or reductive termination." Pure and Applied Chemistry 72, no. 7 (January 1, 2000): 1327–34. http://dx.doi.org/10.1351/pac200072071327.

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Neurotoxic organotin reagents currently play a key role in radical chemistry. As a result, this is an important area for development of new clean replacement reactions. The pharmaceutical industry in particular has had to avoid use of radical methodology for the formation of carbon_carbon bonds for this reason. With the current dawn in green chemistry, a host of new clean radical methods is beginning to flourish. Our aim has been to develop new nontoxic methodology for carbon_carbon bond formation by radical chemistry, which would provide either reductive termination (giving a hydrogen atom to the ultimate radical, as happens with tributyltin hydride), or oxidative functionalization, installing a useful polar group at the site of the ultimate radical. Two methods for effecting radical reactions in an environmentally friendly way are presented: (i) The tetrathiafulvalene (TTF)-mediated radical-polar crossover reaction converts arenediazonium salts to aryl radicals, which have sufficient lifetime to cyclize onto alkenes—the resulting alkyl radicals couple with TTF+• to afford sulfonium salts which, in turn, undergo solvolysis to alcohols, ethers or amides. The method provides the key step in a synthesis of (±)-aspidospermidine. (ii) Hypophosphite salts and hypophosphorous acid, on the other hand, form C_C bonds with reductive termination. These economical reagents afford radicals efficiently, starting from aryl iodides, alkyl bromides, and alkyl iodides, and give very easy separation of products from by-products.

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16

Khudyakov, Igor, Peter Levin, and Aleksei Efremkin. "Cage Effect under Photolysis in Polymer Matrices." Coatings 9, no. 2 (February 12, 2019): 111. http://dx.doi.org/10.3390/coatings9020111.

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Photoinduced elementary reactions of low-MW compounds in polymers is an area of active research. Cured organic polymer coatings often undergo photodegradation by free-radical paths. Besides practical importance, such studies teach how the polymer environment controls elementary free-radical reactions. Presented here is a review of recent literature which reports such studies by product analysis and by a time-resolve technique of photochemical reaction inside the cage of a polymer and in the bulk of a polymer. It was established that application of moderate external magnetic field allows the control of the kinetics of free radicals in elastomers. Preheating and stretching of elastomers affect reactivity of photoproduced radicals.

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17

Elliot, A. John, Shahsultan Padamshi, and Jana Pika. "Free-radical redox reactions of uranium ions in sulphuric acid solutions." Canadian Journal of Chemistry 64, no. 2 (February 1, 1986): 314–20. http://dx.doi.org/10.1139/v86-053.

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The radiolytic reduction of uranyl ions in degassed sulphuric acid solutions containing various organic solutes was studied. It was shown that while ĊOOH, CO2−, and α-hydroxy-alkyl radicals reduced uranyl ions, the β-hydroxy-alkyl radicals and those derived from gluconic acid could not affect the reduction. The oxidation of uranium(IV) by hydrogen peroxide at pH 0.7 involves hydroxyl radicals in a chain mechanism but at pH 2.0 the oxidation proceeds by a non-radical reaction pathway. From the enhancement of the rate of oxidation of uranium(IV) by oxygen in the presence of 2-propanol, a mechanism involving the perhydroxyl radical, which reconciles earlier published data on kinetics and oxygen tracer studies, is proposed for the oxygen-uranium(IV) reactions.

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18

Badanov, S. V., A. V. Urumov, V. V. Bayandin, and N. S. Shaglaeva. "Reactivity of 2,3-Dichloropropene in free-radical copolymerization reactions." Proceedings of Universities. Applied Chemistry and Biotechnology 11, no. 4 (January 6, 2022): 517–22. http://dx.doi.org/10.21285/2227-2925-2021-11-4-517-522.

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The copolymers of 2,3-Dichloropropene with vinyl chloride, methyl methacrylate, and styrene of different compositions were obtained via free-radical copolymerization. The copolymerization constants for the comonomers were found from the dependence of the copolymer composition on the initial mixture content. An increase in the content of 2,3-Dichloropropene in the initial mixture was found to decrease the yield and intrinsic viscosity of the copolymer for all systems. The reactivity of 2,3-Dichloropropene in copolymerization reactions was assessed according to the reciprocals of the copolymerization constants of vinyl chloride, methyl methacrylate, and styrene, which indicate the reactivity of the dichlorinated monomer when interacting with comonomer radicals. It was found that 2,3-dichloropropene is the most active in the reaction with a styrene radical. However, its reactivity with a methyl methacrylate radical decreases by a factor of 0.88 as compared to the styrene radical. The lowest reactivity of 2,3-Dichloropropene is observed when interacting with a vinyl chloride radical. The synthesized copolymers can be further modified by replacing chlorine atoms with functional groups.

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19

Boger, Dale L., and Robert J. Mathvink. "Tandem free-radical alkene addition reactions of acyl radicals." Journal of the American Chemical Society 112, no. 10 (May 1990): 4003–8. http://dx.doi.org/10.1021/ja00166a043.

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20

JONSSON, M., J. LIND, T. REITBERGER, T. E. ERIKSEN, and G. MERENYI. "ChemInform Abstract: Free Radical Combination Reactions Involving Phenoxyl Radicals." ChemInform 24, no. 47 (August 20, 2010): no. http://dx.doi.org/10.1002/chin.199347094.

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21

Taiwo, F. A., H. J. Powers, E. Nakano, H. R. Griffiths, and D. F. Nugent. "Free radical reactions in atherosclerosis; An EPR spectrometry study." Spectroscopy 20, no. 2 (2006): 67–80. http://dx.doi.org/10.1155/2006/474183.

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The copper catalysed oxidation of homocysteine has been studied by electron paramagnetic resonance (EPR) spectroscopy and spin trapping techniques to determine the nature of free radical species formed under varying experimental conditions. Three radicals; thiyl, alkyl and hydroxyl were detected with hydroxyl being predominant. A reaction mechanism is proposed involving Fenton chemistry. Inclusion of catalase to test for intermediate generation of hydrogen peroxide showed a marked reduction in amount of hydroxyl radical generated. In contrast, the addition of superoxide dismutase showed no significant effect on the level of hydroxyl radical formed. Enhanced radical formation was observed at higher levels of oxygen, an effect which has consequences for differential oxygen levels in arterial and venous systems. Implications are drawn for a higher incidence of atherosclerotic plaque formation in arteries versus veins.

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22

M. Silaev, Michael. "Kinetics of Free-Radical Addition Processes by the Nonbranched-Chain Mechanism." Journal of Advance Research in Applied Science (ISSN: 2208-2352) 3, no. 10 (October 31, 2016): 01–19. http://dx.doi.org/10.53555/nnas.v3i10.645.

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Five reaction schemes are suggested for the initiated nonbranched-chain addition of free radicals to the multiple bonds of the unsaturated compounds. The proposed schemes include the reaction competing with chain propagation reactions through a reactive free radical. The chain evolution stage in these schemes involves three or four types of free radicals. One of them is relatively low-reactive and inhibits the chain process by shortening of the kinetic chain length. Based on the suggested schemes, nine rate equations (containing one to three parameters to be determined directly) are deduced using quasi-steady-state treatment. These equations provide good fits for the nonmonotonic (peaking) dependences of the formation rates of the molecular products (1:1 adducts) on the concentration of the unsaturated component in binary systems consisting of a saturated component (hydrocarbon, alcohol, etc.) and an unsaturated component (alkene, allyl alcohol, formaldehyde, or dioxygen). The unsaturated compound in these systems is both a reactant and an autoinhibitor generating low-reactive free radicals. A similar kinetic description is applicable to the nonbranched-chain process of the free-radical hydrogen oxidation, in which the oxygen with the increase of its concentration begins to act as an oxidation autoingibitor (or an antioxidant). The energetics of the key radical-molecule reactions is considered.

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23

Maafa, Ibrahim M. "Inhibition of Free Radical Polymerization: A Review." Polymers 15, no. 3 (January 17, 2023): 488. http://dx.doi.org/10.3390/polym15030488.

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Polymerization reactions have caused several severe accidents in the past since they are prone to runaways due to their highly exothermic and auto-accelerating nature. The heat generated during these uncontrolled runaway reactions surpasses the heat removal capacity of the cooling system leading to the auto-acceleration of the reactions. If proper measures are not taken to attenuate this auto-accelerative nature, dangerous consequences ensue, such as rampant boiling of the reaction system fluids or vapor production from secondary reactions. Both these consequences may eventually lead to over-pressurization followed by a thermal explosion. Thus, to eliminate the associated risk, polymerization reactions in industries are carried out in the presence of inhibitors which are injected into the reaction system before the initiation of polymerization. In this review, I have summarized various accidents that have happened in the past due to runaway polymerization implicating that there is an urgent necessity to do further research in this relatively less explored field of polymerization inhibition. To this end, I have completed an exhaustive survey of the various types of inhibitors used in industries and their inhibition mechanisms focusing mainly on the auto-initiated polymerization of styrene, methyl methacrylate, and acrylic acid monomer. Lastly, the synergism in the inhibition performance of a mixture of two types of inhibitors was also compared and discussed in detail.

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24

MONIZ-BARRETO, PEDRO, and DAVID A. FELL. "Simulation of dioxygen free radical reactions." Biochemical Society Transactions 21, no. 3 (August 1, 1993): 256S. http://dx.doi.org/10.1042/bst021256s.

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25

Yamazaki, I., M. Tamura, R. Nakajima, and M. Nakamura. "Physiological aspects of free-radical reactions." Environmental Health Perspectives 64 (December 1985): 331–42. http://dx.doi.org/10.1289/ehp.8564331.

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26

Chuang, Che-Ping. "Sodiump-Toluenesulfinate in Free Radical Reactions." Synthetic Communications 23, no. 17 (September 1993): 2371–80. http://dx.doi.org/10.1080/00397919308011122.

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27

Myrvold, Bernt O. "Free radical gelling reactions of lignosulfonates." Holzforschung 69, no. 9 (November 1, 2015): 1089–96. http://dx.doi.org/10.1515/hf-2014-0195.

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Abstract Eleven different lignosulfonates (LS) and nine different free radical initiators have been tested in different concentrations to study the possibility of forming LS gels. It was found that the initiator must have a potential high enough for oxidizing the phenolic groups but not so high that would lead to a complete destruction of the LS. The chemical changes of the LS with different oxidants were observed in tests with low concentration of LS. The course of the reaction depends strongly on the type of oxidants that are able to gel the LS.

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28

Holley, A. E., and K. H. Cheeseman. "Measuring free radical reactions in vivo." British Medical Bulletin 49, no. 3 (1993): 494–505. http://dx.doi.org/10.1093/oxfordjournals.bmb.a072626.

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29

H�weler, Udo, and Martin Klessinger. "A model for free-radical reactions." Theoretica Chimica Acta 67, no. 6 (July 1985): 485–90. http://dx.doi.org/10.1007/bf00528143.

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30

Yamazaki, Isao. "Free radical mechanisms in enzyme reactions." Free Radical Biology and Medicine 3, no. 6 (January 1987): 397–404. http://dx.doi.org/10.1016/0891-5849(87)90018-9.

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31

Antropova, Irina G., Elena S. Kurakina, Eldar P. Magomedbekov, and Phyo Myint Oo. "Coumarin reactivity in free radical reactions." Journal of Radioanalytical and Nuclear Chemistry 321, no. 3 (July 19, 2019): 823–29. http://dx.doi.org/10.1007/s10967-019-06666-8.

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32

Cadot, Christine, Peter I. Dalko, Janine Cossy, Cyril Ollivier, Rachel Chuard, and Philippe Renaud. "Free-Radical Hydroxylation Reactions of Alkylboronates." Journal of Organic Chemistry 67, no. 21 (October 2002): 7193–202. http://dx.doi.org/10.1021/jo0201833.

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33

Sibi, Mukund P., and Ned A. Porter. "ChemInform Abstract: Enantioselective Free Radical Reactions." ChemInform 30, no. 20 (June 15, 2010): no. http://dx.doi.org/10.1002/chin.199920287.

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34

Dowd, Paul, and Soo-Chang Choi. "Novel free radical ring-expansion reactions." Tetrahedron 45, no. 1 (January 1989): 77–90. http://dx.doi.org/10.1016/0040-4020(89)80035-3.

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35

Zimmerman, Joke, Amanda Halloway, and Mukund P. Sibi. "ChemInform Abstract: Free Radical Cyclization Reactions." ChemInform 41, no. 37 (August 19, 2010): no. http://dx.doi.org/10.1002/chin.201037267.

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36

ZHDANOV, R. I. "ChemInform Abstract: Nitroxyl Radicals and Non-Radical Reactions of Free Radicals." ChemInform 24, no. 31 (August 20, 2010): no. http://dx.doi.org/10.1002/chin.199331310.

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37

Kremer, Mordechai L. "Initial Steps in the Reaction of H2O2 with Fe2+ and Fe3+ Ions: Inconsistency in the Free Radical Theory." Reactions 4, no. 1 (February 20, 2023): 171–75. http://dx.doi.org/10.3390/reactions4010010.

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Consideration of the changes in free energy shows that the assumed initial steps in reactions of H2O2 with Fe2+ and Fe3+ in the free radical theory are not consistent. The free radical theory is unable to account for the Fe3+-initiated decomposition of H2O2 or for oxidations by it. In reactions with Fe2+ ions at high [H2O2], where O2 evolution reaches a limit, such limit is not foreseen by the free radical model. At lower [H2O2], because of a disallowed substitution in the equation used, the interpretation is not valid. It appears, therefore, that free radicals derived from H2O2 do not provide a suitable basis for constructing models for these reactions. Non-radical models are more successful in interpreting experimental results.

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38

Silaev, M. M. "Competition Kinetics of the Nonbranched-Chain Addition of Free Radicals to Olefins, Formaldehyde, and Oxygen." International Journal of Chemical Engineering 2011 (2011): 1–19. http://dx.doi.org/10.1155/2011/830610.

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Five reaction schemes are suggested for the initiated nonbranched-chain addition of free radicals to the multiple bonds of alkenes, formaldehyde, and oxygen. The schemes include reactions competing with chain propagation through a reactive free radical. The chain evolution stage in these schemes involves three or four types of free radicals. One of them— , , , , or —is relatively low-reactive and inhibits the chain process by shortening of the kinetic chain length. Based on the suggested schemes, nine rate equations containing one to three parameters to be determined directly are set up using quasi-steady-state treatment. These equations provide good fits for the nonmonotonic (peaking) dependences of the formation rates of the molecular addition products (1 : 1 adducts) on the concentration of the unsaturated component in liquid homogeneous binary systems consisting of a saturated component (hydrocarbon, alcohol, etc.) and an unsaturated component (olefin, formaldehyde, or dioxygen). The unsaturated compound in these systems is both a reactant and an autoinhibitor generating low-reactive free radicals. A similar kinetic description is applicable to nonbranched-chain free-radical hydrogen oxidation. The energetics of the key radical-molecule reactions is considered.

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39

Michail, Karim, Naif Aljuhani, and Arno G. Siraki. "The interaction of diamines and polyamines with the peroxidase-catalyzed metabolism of aromatic amines: a potential mechanism for the modulation of aniline toxicity." Canadian Journal of Physiology and Pharmacology 91, no. 3 (March 2013): 228–35. http://dx.doi.org/10.1139/cjpp-2012-0253.

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Synthetic and biological amines such as ethylenediamine (EDA), spermine, and spermidine have not been previously investigated in free-radical biochemical systems involving aniline-based drugs or xenobiotics. We aimed to study the influence of polyamines in the modulation of aromatic amine radical metabolites in peroxidase-mediated free radical reactions. The aniline compounds tested caused a relatively low oxidation rate of glutathione in the presence of horseradish peroxidase (HRP), and H2O2; however, they demonstrated marked oxygen consumption when a polyamine molecule was present. Next, we characterized the free-radical products generated by these reactions using spin-trapping and electron paramagnetic resonance (EPR) spectrometry. Primary and secondary but not tertiary polyamines dose-dependently enhanced the N-centered radicals of different aniline compounds catalyzed by either HRP or myeloperoxidase, which we believe occurred via charge transfer intermediates and subsequent stabilization of aniline-derived radical species as suggested by isotopically labeled aniline. Aniline/peroxidase reaction product(s) were monitored at 435 nm by kinetic spectrophotometry in the presence and absence of a polyamine additive. Using gas chromatography – mass spectrometry, the dimerziation product of aniline, azobenzene, was significantly amplified when EDA was present. In conclusion, di- and poly-amines are capable of enhancing the formation of aromatic-amine-derived free radicals, a fact that is expected to have toxicological consequences.

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40

Huang, Zhipeng, Yang Yang, Junju Mu, Genheng Li, Jianyu Han, Puning Ren, Jian Zhang, Nengchao Luo, Ke-Li Han, and Feng Wang. "Controlling the reactions of free radicals with metal-radical interaction." Chinese Journal of Catalysis 45 (February 2023): 120–31. http://dx.doi.org/10.1016/s1872-2067(22)64181-0.

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41

Beltrán, Fernando J., Manuel Checa, Javier Rivas, and Juan F. García-Araya. "Modeling the Mineralization Kinetics of Visible Led Graphene Oxide/Titania Photocatalytic Ozonation of an Urban Wastewater Containing Pharmaceutical Compounds." Catalysts 10, no. 11 (October 30, 2020): 1256. http://dx.doi.org/10.3390/catal10111256.

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In a water ozonation process, dissolved organics undergo two reactions at least: direct ozone attack and oxidation with hydroxyl radicals generated from the ozone decomposition. In the particular case of urban wastewater contaminated with pharmaceuticals, competition between these two reactions can be studied through application of gas–liquid reaction kinetics. However, there is a lack in literature about kinetic modeling of ozone processes in water specially in photocatalytic ozonation. In this work, lumped reactions of ozone and hydroxyl radicals with total organic carbon have been proposed. Urban wastewater containing a mixture of eight pharmaceutical compounds has been used to establish the kinetic model that simulates the mineralization process. The kinetic model is based on a mechanism of free radical and molecular reactions and the knowledge of mass transfer, chemical reaction rate constants, and radiation transfer data. According to the model, both single ozonation and photocatalytic ozonation present two distinct reaction periods characterized by the absence and presence of dissolved ozone. In the first period (less than 10 min), pharmaceuticals mainly disappear by direct ozone reactions and TOC variation due to these compounds has been modeled according to gas–liquid reaction kinetics through a lumped ozone-pharmaceutical TOC fast second order reaction. The corresponding rate constant of this reaction was found to change with time from 3 × 105 to 200 M−1 s−1 with Hatta values higher than 0.3. In the second period (nearly 5 h), competition between direct and hydroxyl radical reactions takes place and a kinetic model based on a direct and free radical reaction mechanism is proposed. Main influencing parameters to be known were: Direct ozone reaction rate constant, catalyst quantum yield, and hydroxyl radical scavengers. The first two take values of 0.5 M−1 s−1 and 5 × 10−4 mol·photon−1, respectively, while a fraction of TOC between 10% and 90% that changes with time was found to possess hydroxyl radical scavenger nature.

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42

Romodin, Leonid A. "Chemiluminescence Detection in the Study of Free-Radical Reactions. Part 1." Acta Naturae 13, no. 3 (November 15, 2021): 90–100. http://dx.doi.org/10.32607/actanaturae.10912.

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The present review, consisting of two parts, considers the application of the chemiluminescence detection method in evaluating free radical reactions in biological model systems. The first part presents a classification of experimental biological model systems. Evidence favoring the use of chemiluminescence detection in the study of free radical reactions, along with similar methods of registering electromagnetic radiation as electron paramagnetic resonance, spectrophotometry, detection of infrared radiation (IR spectrometry), and chemical methods for assessing the end products of free radical reactions, is shown. Chemiluminescence accompanying free radical reactions involving lipids has been the extensively studied reaction. These reactions are one of the key causes of cell death by either apoptosis (activation of the cytochrome c complex with cardiolipin) or ferroptosis (induced by free ferrous ions). The concept of chemiluminescence quantum yield is also discussed in this article. The second part, which is to be published in the next issue, analyzes the application of chemiluminescence detection using luminescent additives that are called activators, a.k.a. chemiluminescence enhancers, and enhance the emission through the tripletsinglet transfer of electron excitation energy from radical reaction products, followed by light emission with a high quantum yield.

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43

Goez, Martin, Isabell Frisch, and Ingo Sartorius. "Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP." Beilstein Journal of Organic Chemistry 9 (February 26, 2013): 437–46. http://dx.doi.org/10.3762/bjoc.9.46.

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The photoreactions of diazabicyclo[2,2,2]octane (DABCO) and triisopropylamine (TIPA) with the sensitizers anthraquinone (AQ) and xanthone (XA) or benzophenone (BP) were investigated by time-resolved photo-CIDNP (photochemically induced dynamic nuclear polarization) experiments. By varying the radical-pair concentration, it was ensured that these measurements respond only to self-exchange reactions of the free amine-derived radicals (radical cations DH • + or α-amino alkyl radicals D • ) with the parent amine DH; the acid–base equilibrium between DH • + and D • also plays no role. Although the sensitizer does not at all participate in the observed processes, it has a pronounced influence on the CIDNP kinetics because the reaction occurs through successive radical pairs. With AQ, the polarizations stem from the initially formed radical-ion pairs, and escaping DH • + then undergoes electron self-exchange with DH. In the reaction sensitized with XA (or BP), the polarizations arise in a secondary pair of neutral radicals that is rapidly produced by in-cage proton transfer, and the CIDNP kinetics are due to hydrogen self-exchange between escaping D • and DH. For TIPA, the activation parameters of both self-exchange reactions were determined. Outer-sphere reorganization energies obtained with the Marcus theory gave very good agreement between experimental and calculated values of ∆G ‡ 298.

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Bulgakov, V. G., V. F. Tatarinov, and N. S. Gavryushenko. "Tribochemical Component of Oxidative Stress Development at Artificial Joints Implantation. Part 5. Pro-oxidative Properties and Interrelation of Titanium and Non-Metallic Orthopaedic Material Wear Particles with Antioxidants." Vestnik travmatologii i ortopedii imeni N.N. Priorova, no. 3 (September 30, 2015): 41–44. http://dx.doi.org/10.32414/0869-8678-2015-3-41-44.

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Radical-forming ability of artificial wear particles of BT6 titanium alloy and nonmetallic materials was studied using modelling reaction of cumene oxidation. It was stated that alloy particles initiate formation of radicals and consecutive repeated cumene oxidation by metallic particles took place with significantly higher rate of radicals’ formation. Particles of nonmetallic materials (polyethylene, corundum ceramics, carbon nanocomposite) are inert and do not possess radical-forming ability that ensures their advantage in prevention of possible development of adverse free radical reactions in surrounding implant tissues.

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Bulgakov, V. G., V. F. Tatarinov, and N. S. Gavryushenko. "Tribochemical Component of Oxidative Stress Development at Artificial Joints Implantation. Part 5. Pro-oxidative Properties and Interrelation of Titanium and Non-Metallic Orthopaedic Material Wear Particles with Antioxidants." N.N. Priorov Journal of Traumatology and Orthopedics 22, no. 3 (September 15, 2015): 41–44. http://dx.doi.org/10.17816/vto201522341-44.

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Radical-forming ability of artificial wear particles of BT6 titanium alloy and nonmetallic materials was studied using modelling reaction of cumene oxidation. It was stated that alloy particles initiate formation of radicals and consecutive repeated cumene oxidation by metallic particles took place with significantly higher rate of radicals’ formation. Particles of nonmetallic materials (polyethylene, corundum ceramics, carbon nanocomposite) are inert and do not possess radical-forming ability that ensures their advantage in prevention of possible development of adverse free radical reactions in surrounding implant tissues.

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46

Chumakov, Anton A., Valentina N. Batalova, Yuriy G. Slizhov, and Tamara S. Minakova. "VERIFICATION OF NON-CATALYTIC HYDROGEN PEROXIDE DISPROPORTIONATION MECHANISM BY THERMODYNAMIC ANALYSIS OF ONE-ELECTRON REDOX REACTIONS." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 60, no. 6 (July 19, 2017): 40. http://dx.doi.org/10.6060/tcct.2017606.5529.

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There is two-electron transfer during the process of hydrogen peroxide decomposition into water and oxygen. The detailed mechanism of non-catalytic hydrogen peroxide disproportionation is not verified until now. We assumed that any poly-electron redox process is a complex and consists of one-electron redox reactions. We have formulated equations of possible one-electron transfers during hydrogen peroxide disproportionation. Based on known laws and equations of thermochemistry we calculated standard thermodynamic functions for a total reaction and each one-elect-ron redox reaction using reference values of standard thermodynamic functions of reagents and products of reactions. Results show that the total reaction leads to significant decrease in Gibbs free energy -246.0 kJ/mol in gas phase but there is increase +39.9 kJ/mol in Gibbs free energy during the first proposed step. It is substantiation for known dependence of hydrogen peroxide dismutation kinetics at thermal, photochemical or catalytic activation. The first proposed step of non-catalytic process is one-electron plus one-proton transfer in thermally or photochemically activated dimeric hydrogen peroxide associate (H2O2)2 with simultaneous generation of hydroperoxyl HO2• and hydroxyl HO• free radicals and water molecule. There is thermodynamic argumentation for radical chain mechanism of hydrogen peroxide disproportionation after the activation. We made the graphic illustration of thermodynamically supported scheme of non-catalytic hydrogen peroxide decomposition. There is a cyclic alternation of two radical-molecular interactions during the hydrogen peroxide chain decomposition. The hydroxyl radical generates the hydroperoxyl radi-cal from a hydrogen peroxide molecule and then the hydroperoxyl radical interacts with a next hydrogen peroxide molecule followed by the hydroxyl radical generation. Interactions between the homonymic or heteronymic free radicals are the reactions of chain breaking.Forcitation:Chumakov A.A., Batalova V.N., Slizhov Yu.G., Minakova T.S. Verification of non-catalytic hydrogen peroxide disproportionation mechanism by thermodynamic analysis of one-electron redox reactions. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 6. P. 40-44.

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Wu, Yuh-Wern, and Cheng-Yi Lu. "The Competitive Reactions between Electron Transfer and Radical Addition in Free Radical Reactions." Journal of the Chinese Chemical Society 48, no. 6B (December 2001): 1129–34. http://dx.doi.org/10.1002/jccs.200100167.

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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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Eastwood, FW, RD Mifsud, and P. Perlmutter. "Acyclic Stereocontrol of Free Radical Reactions Involving Alkyl 2-(1-Hydroxyalkyl)propenoates." Australian Journal of Chemistry 47, no. 12 (1994): 2187. http://dx.doi.org/10.1071/ch9942187.

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The addition of cyclohexyl and t-butyl free radicals to silylated derivatives of alkyl 2-(1-hydroxyalkyl) propenoates was found to be stereoselective . In the case of the cyclohexyl radical the stereoselectivity was dependent upon the conditions used to generate the free radical and to quench the intermediate. Stereoselectivity in additions of the t-butyl radical was found to be temperature-dependent. In all cases stereoselectivity increased as the steric bulk of the group attached to the carbinol oxygen increased. A simple model which accounts for the stereoselectivity is proposed.

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Wiegel, Aaron A., Matthew J. Liu, William D. Hinsberg, Kevin R. Wilson, and Frances A. Houle. "Diffusive confinement of free radical intermediates in the OH radical oxidation of semisolid aerosols." Physical Chemistry Chemical Physics 19, no. 9 (2017): 6814–30. http://dx.doi.org/10.1039/c7cp00696a.

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