Artykuły w czasopismach na temat „Radical”
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Huang, Danqing, Dirk Geeraerts i Weiwei Zhang. "A diachronic analysis of the FIRE character". Chinese Semiotic Studies 17, nr 1 (14.01.2021): 1–44. http://dx.doi.org/10.1515/css-2021-0001.
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Abstract Chinese radicals are the semantic components of Chinese characters that generally indicate major concepts and categories. Characters that share the same radical may be semantically linked in various ways to the broad semantic category that the radical represents, and radicals may thus be considered a categorization mechanism to distinguish lexical meanings. Given the fact that FIRE is an independent character that can also be used as a radical in composite characters, the question arises as to what extent the semantic developments of the FIRE character and the FIRE radical are similar, i.e. does the FIRE radical develop independently of the FIRE character? Against the background of this question, this paper studies the diachronic semantic structure of the FIRE character, which will be compared to the FIRE radical in composite characters in follow-up studies. The analysis shows that the overall diachronic development of the FIRE character exhibits prototypical characteristics and a radial network structure.
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Muchnik, Pablo. "Radical Evil (radikal Böse)". Estudos Kantianos [EK] 6, nr 2 (29.01.2019): 101–6. http://dx.doi.org/10.36311/2318-0501.2018.v6n2.20.p101.
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By “evil,” Kant does not designate any set of particularly pernicious acts, but the type of volition that underlies and makes possible immorality in all its forms. The evil person, Kant believes, “makes the incentives of self-love and their inclinations the condition of compliance with the moral law –whereas it is the latter that, as the supreme condition of the satisfaction of the former, should have been incorporated into the universal maxim of the power of choice as the sole incentive” (R 6:36). This inversion of the ethical order of priority does not entail the repudiation of “the moral law (…) in rebellious attitude (by revoking obedience to it)” (R 6:36), but its conditional respect. This fraudulent relation to morality is based on complex strategies of deception, self-deception, and rationalization. The “radical “nature of these tendencies has nothing to do with the intensity or magnitude of observable wrongdoing. Evil’s radicalism is a spatial metaphor intended to designate the locus of immorality (its “root”) in an agent’s “disposition (Gesinnung). What is most baffling the Kantian view is that evil so construed is perfectly compatible with good conduct. Indeed, under the conditions of civilization, Kant believes, it is impossible to distinguish a man of good conduct from a morally good man (RGV 6:30), for the dictates of self-love generally overlap with the prescriptions of duty. The persistence of war, poverty, oppression, and the infinity of vices which cast a dark shadow over the contemporary world speak of the prescience of the Kantian approach.
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Sands, A. D. "Radicals and one-sided ideals". Proceedings of the Royal Society of Edinburgh: Section A Mathematics 103, nr 3-4 (1986): 241–51. http://dx.doi.org/10.1017/s0308210500018898.
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The correspondence between radicals of associative rings and A-radicals is studied. It is shown that corresponding to each A-radical there is an interval of radicals and that each radical belongs to exactly one such interval. The question of the nature of the radical of a one-sided ideal is considered. It is shown that the radicals such that the radical of a one-sided ideal is always a one-sided ideal are those which contain their associated A-radicals. Radicals such that the radical of a one-sided ideal always equals the intersection of a left ideal and a right ideal are described, as are those A-radicals such that every associated radical has this property.
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Kyne, Sara H., i Carl H. Schiesser. "Ab Initio Studies of Carbonyl Radical Additions to Hydrazone Systems". Australian Journal of Chemistry 62, nr 7 (2009): 728. http://dx.doi.org/10.1071/ch09165.
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Ab initio and DFT calculations reveal that intermolecular radical additions of both acyl and oxyacyl radials to hydrazones occur through SOMO → π*hydrazone, πhydrazone → SOMO and LPN → SOMO interactions between the radical and the hydrazone π-system. Both acetyl and methoxycarbonyl radicals show preference for addition to the carbon end of the carbon–nitrogen π-bond. At the highest level of theory used in this study (G2//MP2(full)/6-31G*), energy barriers of 11.2 and 22.6 kJ mol–1 are calculated for acetyl radical addition to the carbon and nitrogen-ends of N-aminomethanimine respectively. The analogous energy barriers for the methoxycarbonyl radical are 4.9 and 25.7 kJ mol–1 at the same level of theory.
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Adrian, Gerild, Edi Suryanto i Defny S. Wewengkang. "AKTIVITAS PENANGKAL RADIKAL BEBAS DARI FRAKSI KULIT KAYU SAGU BARUK (Arenga microcarpha Beccari)". PHARMACON 10, nr 1 (24.02.2021): 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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Kajiwara, Atsushi. "Characterizations of radicals formed in radical polymerizations and transfer reactions by electron spin resonance spectroscopy". Pure and Applied Chemistry 90, nr 8 (28.08.2018): 1237–54. http://dx.doi.org/10.1515/pac-2018-0401.
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Abstract Electron spin resonance (ESR, aka electron paramagnetic resonance, EPR) investigations have been conducted on radicals formed during radical polymerizations and provide a detailed characterization of the active radical species. Active propagating radicals can be observed during actual radical polymerizations by ESR/EPR. The chain lengths of the observed radicals were estimated by a combination of atom transfer radical polymerization (ATRP) and ESR/EPR. The structures of the chain end radicals were determined by analysis of the ESR/EPR spectra. An increase in the dihedral angles between terminal p-orbital of radical and Cβ–H bonds was observed with increasing chain lengths of methacrylate polymers. Radical transfer reactions were observed during radical polymerization of acrylates. A combination of ATRP and ESR/EPR clarified a 1,5-hydrogen shift mechanism of the radical transfer reactions using model adamantyl acrylate radicals. Penultimate unit effects were also observed. Time-resolved ESR/EPR (TR ESR) spectroscopy clarified the initiation processes of an alternating copolymerization of styrene with maleic anhydride and the copolymerization of styrene with 1,3-butadiene. Several unsolved problems in conventional radical polymerization processes have been clarified using combinations of ATRP with ESR/EPR and TR ESR. Characterization of the radicals in radical polymerizations using various ESR techniques would definitely provide interesting and useful information on conventional radical polymerizations.
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Kuznetsova, A. V., i S. V. Kuzmina. "THE EVOLUTION OF THE LEFT RADICAL PARTIES AND MOVEMENTS IN WESTERN EUROPE AND RUSSIA". KAZAN SOCIALLY-HUMANITARIAN BULLETIN 11, nr 6 (grudzień 2020): 49–53. http://dx.doi.org/10.24153/2079-5912-2020-11-6-49-53.
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A round table on the evolution of the Western European radical left parties and movements was held online on November 19, 2020. The participants of the round table presented reports and discussed such key cases of the radical left parties as Podemos, the Unconquered France and SYRIZA. In addition, they discussed what impact the Latin American experience had on the radical left in Western Europe. In the early 21st century, radial left parties and movements in Western Europe experienced an upsurge, which was largely triggered by the 2008 financial crisis. The rise of the several radial left parties was also fueled by the mass protests that continued in Europe throughout 2010. Currently, the radical left party Podemos in Spain has lost some of its supporters and faced the need to either sacrifice its principled position or be replaced by other parties. The Unconquered France also lost a significant number of votes in the 2017 elections. Finally, the most successful of the European radical left parties - SYRIZA in Greece - also lost parliamentary elections in 2019 and was forced to become the main opposition party. The roundtable participants agreed that with the rise to power, left radicals are forced to significantly change their political discourse, deradicalize and adapt to the existing rules of the game. Radical left movements in Latin America have had an undeniable impact on the Western European left. The speakers also noted that the development of the radical left ideas in Russia differs significantly from those in Western Europe. Today, the Russian radical left has no significant influence on the political arena. This article summarizes the main aspects of the academic presentations and the discussions that accompanied them.
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Sueishi, Yoshimi, Daisuke Yoshioka, Shigeru Oowada, Nobuyuki Endoh, Shunji Kohri, Hirotada Fujii, Masashi Shimmei i Yashige Kotake. "Is the Oxygen Radical Absorbance Capacity (ORAC) Method a Peroxyl-radical Scavenging Assay?" Zeitschrift für Physikalische Chemie 224, nr 06 (1.07.2010): 921–28. http://dx.doi.org/10.1524/zpch.2010.5536.
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AbstractThe oxygen radical absorbance capacity (ORAC) method employs a water soluble azo-radical initiator, AAPH (2,2’-azobis(2-amidinopropane) dihydrochloride) as a free radical generator, by which the fluorescent probe fluorescein is damaged to result in the loss of fluorescence. Antioxidants can protect the probe from the damage and the degree of protection is quantified. Because AAPH has been used as a lipid-peroxidation reagent, “oxygen radical” in ORAC is generally accepted as peroxyl radicals; however, in the present spin trapping experiments using a newly developed spin trap, CYPMPO, there was no indication of peroxyl-radical formation in AAPH decomposition in aqueous media. These spin trapping studies demonstrated that alkoxyl (RO·) radical adduct was the sole product of AAPH decomposition. In contrast, alkyl-peroxyl (ROO·) radical was spin-trapped during the decomposition of a lipid soluble azo-radical initiator AIBN (azobis(isobutyronitrile)) in non-aqueous media. We speculate that alkyl-peroxyl radicals are short-lived in water, rapidly converted into alkoxyl radicals. Although the possibility that ORAC method monitors peroxyl-radical scavenging activity cannot be completely eliminated, spin trapping evidence strongly indicates that ORAC method is a scavenging capacity assay for alkoxyl radicals.
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Nemoto, David T., Kang-Jie Bian, Shih-Chieh Kao i Julian G. West. "Radical ligand transfer: a general strategy for radical functionalization". Beilstein Journal of Organic Chemistry 19 (15.08.2023): 1225–33. http://dx.doi.org/10.3762/bjoc.19.90.
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The place of alkyl radicals in organic chemistry has changed markedly over the last several decades, evolving from challenging-to-generate “uncontrollable” species prone to side reactions to versatile reactive intermediates enabling construction of myriad C–C and C–X bonds. This maturation of free radical chemistry has been enabled by several advances, including the proliferation of efficient radical generation methods, such as hydrogen atom transfer (HAT), alkene addition, and decarboxylation. At least as important has been innovation in radical functionalization methods, including radical–polar crossover (RPC), enabling these intermediates to be engaged in productive and efficient bond-forming steps. However, direct engagement of alkyl radicals remains challenging. Among these functionalization approaches, a bio-inspired mechanistic paradigm known as radical ligand transfer (RLT) has emerged as a particularly promising and versatile means of forming new bonds catalytically to alkyl radicals. This development has been driven by several key features of RLT catalysis, including the ability to form diverse bonds (including C–X, C–N, and C–S), the use of simple earth abundant element catalysts, and the intrinsic compatibility of this approach with varied radical generation methods, including HAT, radical addition, and decarboxylation. Here, we provide an overview of the evolution of RLT catalysis from initial studies to recent advances and provide a conceptual framework we hope will inspire and enable future work using this versatile elementary step.
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Zhao, Jing, Mei Wang, Hongfang Yang, Meng Zhang, Ping Liu i Yuxiang Bu. "Radical–Radical Interactions among Oxidized Guanine Bases Including Guanine Radical Cation and Dehydrogenated Guanine Radicals". Journal of Physical Chemistry B 117, nr 37 (6.09.2013): 10698–710. http://dx.doi.org/10.1021/jp4042149.
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Liu, Youjia, Malgorzata Biczysko i Nigel W. Moriarty. "A radical approach to radicals". Acta Crystallographica Section D Structural Biology 78, nr 1 (1.01.2022): 43–51. http://dx.doi.org/10.1107/s2059798321010809.
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Nitroxide radicals are characterized by a long-lived spin-unpaired electronic ground state and are strongly sensitive to their chemical surroundings. Combined with electron paramagnetic resonance spectroscopy, these electronic features have led to the widespread application of nitroxide derivatives as spin labels for use in studying protein structure and dynamics. Site-directed spin labelling requires the incorporation of nitroxides into the protein structure, leading to a new protein–ligand molecular model. However, in protein crystallographic refinement nitroxides are highly unusual molecules with an atypical chemical composition. Because macromolecular crystallography is almost entirely agnostic to chemical radicals, their structural information is generally less accurate or even erroneous. In this work, proteins that contain an example of a radical compound (Chemical Component Dictionary ID MTN) from the nitroxide family were re-refined by defining its ideal structural parameters based on quantum-chemical calculations. The refinement results show that this procedure improves the MTN ligand geometries, while at the same time retaining higher agreement with experimental data.
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Wisniak, Jaime. "Auguste Laurent. Radical and radicals". Educación Química 20, nr 2 (kwiecień 2009): 166–75. http://dx.doi.org/10.1016/s0187-893x(18)30023-5.
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Yañez Jaramillo, Lina M., Joy H. Tannous i Arno de Klerk. "Persistent Free Radicals in Petroleum". Processes 11, nr 7 (11.07.2023): 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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ROTA, Cristina, P. David BARR, V. Martha MARTIN, F. Peter GUENGERICH, Aldo TOMASI i P. Ronald MASON. "Detection of free radicals produced from the reaction of cytochrome P-450 with linoleic acid hydroperoxide". Biochemical Journal 328, nr 2 (1.12.1997): 565–71. http://dx.doi.org/10.1042/bj3280565.
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The ESR spin-trapping technique was employed to investigate the reaction of rabbit cytochrome P-450 1A2 (P450) with linoleic acid hydroperoxide. This system was compared with chemical systems where FeSO4 or FeCl3 was used in place of P450. The spin trap 5,5ʹ-dimethyl-1-pyrroline N-oxide (DMPO) was employed to detect and identify radical species. The DMPO adducts of hydroxyl, O2-•, peroxyl, methyl and acyl radicals were detected in the P450 system. The reaction did not require NADPH-cytochrome P-450 reductase or NADPH. The same DMPO-radical adducts were detected in the FeSO4 system. Only DMPO-•OH radical adduct and carbon-centred radical adducts were detected in the FeCl3 system. Peroxyl radical production was completely O2-dependent. We propose that polyunsaturated fatty acids are initially reduced to form alkoxyl radicals, which then undergo intramolecular rearrangement to form epoxyalkyl radicals. Each epoxyalkyl radical reacts with O2, forming a peroxyl radical. Subsequent unimolecular decomposition of this peroxyl radical eliminates O2-• radical.
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Shukla, D., N. P. Schepp, N. Mathivanan i L. J. Johnston. "Generation and spectroscopic and kinetic characterization of methoxy-substituted phenoxyl radicals in solution and on paper". Canadian Journal of Chemistry 75, nr 12 (1.12.1997): 1820–29. http://dx.doi.org/10.1139/v97-615.
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A number of methoxy-substituted phenoxyl radicals have been generated and characterized by laser flash photolysis techniques in solution and on paper. The radicals have been produced by three routes in solution: hydrogen abstraction from phenols by tert-butoxyl radical, photolysis of α-aryloxyacetophenones, and direct excitation of phenols. Most of the phenoxyl radicals studied have a characteristic absorption near 400 nm; the ortho-substituted radicals have an additional broad absorption in the visible in non-hydroxylic solvents (e.g., 650 nm for 2-methoxyphenoxyl radical). The relative intensities of the 400 nm and the long-wavelength bands vary with substitution pattern and solvent, with the long wavelength band being much weaker in hydroxylic solvents. Direct excitation of phenols provides an alternate source of phenoxyl radicals in some cases. However, for 4-methoxyphenol there are overlapping absorptions due to triplet phenol and phenol radical cation, both of which absorb in the 400–460 nm region. The 4-methoxyphenol radical cation is formed in a biphotonic process and decays by deprotonation to give the phenoxyl radical. The 4-methoxyphenoxyl radical can also be generated on paper from either the ketone or phenol precursor and decays with complex kinetics that depend on the precursor loading and laser intensity. There is no evidence for the formation of significant amounts of long-lived ketone or phenol triplets on paper. The decay kinetics for the phenoxyl radical are modified by the addition of the radical scavenger dithioerythritol. The results indicate both static and dynamic components to the radical scavenging process. The generation of phenoxyl radicals on paper in the presence and absence of scavengers provides the basis for the development of a new method for screening potential photoyellowing inhibitors and understanding their mode of action. Keywords: phenoxyl radicals, paper photoyellowing, laser flash photolysis, triplets, radical cations.
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Majumdar, Subrata, i Kalyan Kumar Dey. "Three Distinct Non-Hereditary Radicals Which Coincide with the Classical Radical for Rings with D.C.C." GANIT: Journal of Bangladesh Mathematical Society 35 (28.06.2016): 1–5. http://dx.doi.org/10.3329/ganit.v35i0.28560.
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Majumdar and Paul [3] introduced and studied a new radical E defined as the upper radical determined by the class of all rings each of whose ideals is idempotent. In this paper the authors continue the study further and also study the join radical and the intersection radical (due to Leavitt) obtained from E and the Jacobson radical J. These have been denoted by E + J and EJ respectively. The radical and the semisimple rings corresponding to E + J and EJ have been obtained. Both of these radicals coincide with the classical nil radical for Artinian rings. Important properties of these radicals and their position among the well-known special radicals have been investigated. It has been proved that E, EJ and E + J are non-hereditary. It has also been proved as an independent result that the nil radical N is not dual, i.e., N ? N?.GANIT J. Bangladesh Math. Soc.Vol. 35 (2015) 1-11
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Shea, Suzanne, Norman P. Schepp, Amy E. Keirstead i Frances L. Cozens. "Dynamics of the transient species generated upon photolysis of diarylmethanes within zeolites Deprotonation and oxidation reactions". Canadian Journal of Chemistry 83, nr 9 (1.09.2005): 1637–48. http://dx.doi.org/10.1139/v05-208.
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The oxidation of diarylmethanes is a multistep process involving initial formation of a radical cation, deprotonation of the radical cation to the radical, and oxidation of the radical to the carbocation. The dynamics and efficiency of the last two steps in this process, namely deprotonation and oxidation, in acidic zeolites and non-acid zeolites are examined in the present work as a function of the acidity of the diarylmethane radical cations and the oxidation potential of the diarylmethyl radicals. Our results indicate that rate constants for deprotonation strongly depend on the acidity of the radical cations, but not on the composition of the zeolites. In addition, oxidation of the radicals to the diarylmethyl cations is strongly dependent on both the oxidation potential of the radicals and the oxidizing ability of the zeolite. This dependence allows oxidation potentials of the zeolites to be estimated.Key words: radical cations, carbocations, zeolites, laser flash photolysis.
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Nakazawa, H., K. Ichimori, Y. Shinozaki, H. Okino i S. Hori. "Is superoxide demonstration by electron-spin resonance spectroscopy really superoxide?" American Journal of Physiology-Heart and Circulatory Physiology 255, nr 1 (1.07.1988): H213—H215. http://dx.doi.org/10.1152/ajpheart.1988.255.1.h213.
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A recent study has indicated that the generation of an oxygen radical in freeze-clamped myocardium on reperfusion can be directly demonstrated using electron-spin resonance spectroscopy (ESR). However, the results need to be analyzed with caution, since artifactual radicals are misleading problems common to this method. To test whether that reported superoxide is truly the biologically existing radical or an artifactual radical, we performed experiments using isolated, perfused rat and rabbit hearts and open-chest canine hearts subjected to ischemia/reperfusion. Radicals were freeze trapped at 77 degrees K, and ESR measurements were made. The ESR spectra exhibited four free radicals. Among these, two radicals which had been previously claimed as superoxide and a nitrogen-centered radical were shown as mechanically yielded artifactual radicals. These were produced by pulverization of the frozen sample. In artifact-free samples, superoxide could not be detected. The radicals native to the myocardium were identified as coenzyme Q10-. and another radical the species of which remains unclear.
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Sahharova, Liliya T., Evgeniy G. Gordeev, Dmitry B. Eremin i Valentine P. Ananikov. "Computational Design of Radical Recognition Assay with the Possible Application of Cyclopropyl Vinyl Sulfides as Tunable Sensors". International Journal of Molecular Sciences 22, nr 14 (16.07.2021): 7637. http://dx.doi.org/10.3390/ijms22147637.
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The processes involving the capture of free radicals were explored by performing DFT molecular dynamics simulations and modeling of reaction energy profiles. We describe the idea of a radical recognition assay, where not only the presence of a radical but also the nature/reactivity of a radical may be assessed. The idea is to utilize a set of radical-sensitive molecules as tunable sensors, followed by insight into the studied radical species based on the observed reactivity/selectivity. We utilize this approach for selective recognition of common radicals—alkyl, phenyl, and iodine. By matching quantum chemical calculations with experimental data, we show that components of a system react differently with the studied radicals. Possible radical generation processes were studied involving model reactions under UV light and metal-catalyzed conditions.
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Yuan, Ningning, Wenqing Wang, Ziye Wu, Sheng Chen, Gengwen Tan, Yunxia Sui, Xinping Wang, Jun Jiang i Philip P. Power. "A boron-centered radical: a potassium-crown ether stabilized boryl radical anion". Chemical Communications 52, nr 86 (2016): 12714–16. http://dx.doi.org/10.1039/c6cc06918e.
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Iwahashi, H., C. E. Parker, R. P. Mason i K. B. Tomer. "Radical adducts of nitrosobenzene and 2-methyl-2-nitrosopropane with 12,13-epoxylinoleic acid radical, 12,13-epoxylinolenic acid radical and 14,15-epoxyarachidonic acid radical. Identification by h.p.l.c.-e.p.r. and liquid chromatography-thermospray-m.s". Biochemical Journal 276, nr 2 (1.06.1991): 447–53. http://dx.doi.org/10.1042/bj2760447.
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Linoleic acid-derived radicals, which are formed in the reaction of linoleic acid with soybean lipoxygenase, were trapped with nitrosobenzene and the resulting radical adducts were analysed by h.p.l.c.-e.p.r. and liquid chromatography-thermospray-m.s. Three nitrosobenzene radical adducts (peaks I, II and III) were detected; these gave the following parent ion masses: 402 for peak I, 402 for peak II, and 386 for peak III. The masses of peaks I and II correspond to the linoleic acid radicals with one more oxygen atom [L(O).]. The radicals are probably carbon-centred, because the use of 17O2 did not result in an additional hyperfine splitting. Computer simulation of the peak I radical adduct e.p.r. spectrum also suggested that the radical is carbon-centred. The peak I radical was also detected in the reaction of 13-hydroperoxylinoleic acid with FeSO4. From the above results, peak I is probably the 12,13-epoxylinoleic acid radical. An h.p.l.c.-e.p.r. experiment using [9,10,12,13-2H4]linoleic acid suggested that the 12,13-epoxylinoleic acid radical is a C-9-centred radical. Peak II is possibly an isomer of peak I. Peak III, which was observed in the reaction mixture without soybean lipoxygenase, corresponds to a linoleic acid radical (L.). The 12,13-epoxylinoleic acid radical, 12,13-epoxylinolenic acid radical and 14,15-epoxyarachidonic acid radical were also detected in the reactions of linoleic acid, linolenic acid and arachidonic acid respectively, with soybean lipoxygenase using nitrosobenzene and 2-methyl-2-nitrosopropane as spin-trapping agents.
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Kim, Eun-Kyung, i Mi Ryeong Song. "Factors Influencing the Level of Oxygen Free Radicals in Female Nursing Students". Global Journal of Health Science 11, nr 7 (15.05.2019): 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 (β = .20, p =. 003), fatigue (β = .20, p = .004), and detox necessity (β = .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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Chen, Tianxu, i Yali Feng. "Nontransparent Compound Character Learning in L2 Chinese: Does Radical Awareness Always Work?" SAGE Open 10, nr 4 (październik 2020): 215824402096966. http://dx.doi.org/10.1177/2158244020969669.
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Chinese character learning requires various reading subskills, such as radical awareness and character knowledge. Radical awareness refers to learners’ ability to identify, analyze, and apply semantic radicals in compound characters. Previous studies have shown that radical awareness and character knowledge facilitate learning semantically transparent characters. Yet, little is known regarding whether radical awareness plays an active role in the meaning retention for nontransparent characters. The meanings of transparent characters, such as “河” (river) containing the radical “氵” (water), are related to the semantic category of the radicals within the characters, whereas the meanings of nontransparent characters, such as “淑” (kind and gentle) with the same radical “氵,” are not directly related to the radicals. To fill these gaps, this study included 39 L2 Chinese learners at one American university. They completed one character-learning session, and five radical-related and character-related tasks. The results suggested that radical awareness did not positively affect the meaning retention for nontransparent characters when learners’ character knowledge was controlled. In addition, character knowledge was a moderator, which shaped the relationship between radical awareness and character retention. Pedagogical implications for the understanding of L2 Chinese compound character learning are discussed.
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Yepsen, Orlando, Lorena Cornejo-Ponce i Rodrigo Yepsen. "Perspectives for Photochemical Leaching Processes of Chalcopyrite: A Solar Radical-Leaching Process". Mining 4, nr 2 (11.05.2024): 352–66. http://dx.doi.org/10.3390/mining4020020.
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This paper review presents a comparison between conventional leaching and advanced photochemical leaching processes and their potential for use in chalcopyrite leaching. Likewise, it presents an analysis of the differences between the advanced leaching processes, photoleaching and radical-leaching, indicating that the photochemical mechanisms (photooxidation/photoreduction and generation of radical oxygen species (ROS) and radical sulfur species (RSS)) would improve the oxidative dissolution of chalcopyrite, taking advantage of the high oxidizing power of free radicals. Initial experimental results of solar-assisted radical-leaching on chalcopyrite are presented, demonstrating that sulfate radicals (SO4−) allow copper to be leached at a rate 4.7 times higher than in the absence of radicals and sunlight. With these results, a radical-leaching process is presented for the first time, with a perspective toward the future development of a new hydrometallurgical route: solar-assisted radical-leaching.
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Bi, Yong Guang, i Chun Chun Liu. "Study on Scavenging Free Radical Activity with Polysaccharides Materials in Chuanxiong Based on Composite Properties of Biomaterials". Advanced Materials Research 583 (październik 2012): 244–47. http://dx.doi.org/10.4028/www.scientific.net/amr.583.244.
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By using spectrophotometric detection of the Chuanxiong polysaccharides on the free radical scavenging. The results show that the Chuanxiong polysaccharides on DPPH radical, hydroxyl radical (HO•) and superoxide anion radical (•) clearance. Scavenging ability with the the Chuanxiong polysaccharide concentration increased, and showed the dose-effect relationship. Concentration of 2.0mg/mL when DPPH radicals clear the rate of 35.61%, while the rate of hydroxyl radicals and superoxide anion radical scavenging, clear the rate of 57.78% and 57.14%. Chuanxiong polysaccharide is an ideal natural antioxidants and good prospects for the development of biomedical composites.
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Lim, Y. B., Y. Tan, M. J. Perri, S. P. Seitzinger i B. J. Turpin. "Aqueous chemistry and its role in secondary organic aerosol (SOA) formation". Atmospheric Chemistry and Physics Discussions 10, nr 6 (9.06.2010): 14161–207. http://dx.doi.org/10.5194/acpd-10-14161-2010.
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Abstract. There is a growing understanding that secondary organic aerosol (SOA) can form through reactions in atmospheric waters (i.e., clouds, fogs, and aerosol water). In clouds and wet aerosols, water-soluble organic products of gas-phase photochemistry dissolve into the aqueous phase where they can react further (e.g. with OH radicals) to form low volatility products that are largely retained in the particle phase. Organic acids, oligomers and other products form via radical- and non-radical reactions, including hemiacetal formation during droplet evaporation, acid/base catalyzation, and reaction of organics with other constituents (e.g. NH4+). This paper uses kinetic modeling, experiments conducted with aqueous carbonyl solutions in the presence and absence of OH radicals, electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry, and the literature to describe aqueous chemistry at cloud- and aerosol-relevant concentrations and during droplet evaporation. At least for aqueous reactions of glyoxal with OH radicals, chemical modeling can reproduce experiments conducted at cloud-relevant concentrations without including radical–radical reactions, whereas radical–radical reactions become dramatically more important at higher concentrations. We demonstrate that reactions with OH radicals tend to be faster and form more SOA than "non-radical" reactions (e.g., acid catalyzation).
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Ilić-Georgijević, Emil. "On graded special radicals of graded rings". Journal of Algebra and Its Applications 17, nr 06 (23.05.2018): 1850109. http://dx.doi.org/10.1142/s0219498818501098.
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In this paper, a graded ring is a ring which is the direct sum of a family of its additive subgroups indexed by a nonempty set under the assumption that the product of homogeneous elements is again homogeneous. We study graded special radicals and special radicals of graded rings, but which contain the corresponding Jacobson radicals. There are two versions of this graded radical, which we name the graded over-Jacobson and the large graded over-Jacobson radical. We establish several characterizations of the graded over-Jacobson radical of a graded ring and also prove that the largest homogeneous ideal contained in the corresponding classical radical of a graded ring coincides with the large graded over-Jacobson radical of that ring.
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Renaud, Philippe, Alice Beauseigneur, Andrea Brecht-Forster, Barbara Becattini, Vincent Darmency, Sarkunam Kandhasamy, Florian Montermini i in. "Boron: A key element in radical reactions". Pure and Applied Chemistry 79, nr 2 (1.01.2007): 223–33. http://dx.doi.org/10.1351/pac200779020223.
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Boron derivatives are becoming key reagents in radical chemistry. Here, we describe reactions where an organoboron derivative is used as a radical initiator, a chain-transfer reagent, and a radical precursor. For instance, B-alkylcatecholboranes, easily prepared by hydroboration of alkenes, represent a very efficient source of primary, secondary, and tertiary alkyl radicals. Their very high sensitivity toward oxygen- and heteroatom-centered radicals makes them particularly attractive for the development of radical chain processes such as conjugate addition, allylation, alkenylation, and alkynylation. Boron derivatives have also been used to develop an attractive new procedure for the reduction of radicals with alcohols and water. The selected examples presented here demonstrate that boron-containing reagents can efficiently replace tin derivatives in a wide range of radical reactions.
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Das, Suresh, i Clemens von Sonntag. "The Oxidation of Trimethylamine by OH Radicals in Aqueous Solution, as Studied by Pulse Radiolysis, ESR, and Product Analysis. The Reactions of the Alkylamine Radical Cation, the Aminoalkyl Radical, and the Protonated Aminoalkyl Radical". Zeitschrift für Naturforschung B 41, nr 4 (1.04.1986): 505–13. http://dx.doi.org/10.1515/znb-1986-0418.
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Hydroxyl radical reactions with trimethylamine in aqueous solution lead to the formation of the aminoalkyl radical (CH3)2NCH2 (A) and its conjugated acid (CH3)2HN+CH2 (AH+) as well as to the alkylamine radical cation (CH3)3N+(N+). These radicals are transform ed into each other by hydrolytic reactions, e.g.[xxx]Radicals AH+ are more acidic (pKa ≈ 3.6) than the radicals N+(pKa ≈ 8.0). Consequently, N+ predom inate over AH+ under quasi equilibrium conditions (e.g. in the presence of phosphate buffer) and are the only species observed by ESR in acid solutions. Reacting with the protonated amine. OH radicals abstract hydrogen at nitrogen and at carbon with comparable ease. Reaction of OH radicals with the free amine may initially also generate N+, beside H-abstraction at carbon. Radicals A’ absorb more strongly at 260 nm (ε = 3390 dm3mol-1cm-1) than the radical cation N+(ε = 950 dm3mol-1cm-1). Radical A' has reducing properties whereas radicals AH+ and N+ have oxidizing properties and hence can be monitored with p-nitroacetophenone (the reducing radicals), and Fe(CN)64- , N ,N'-tetramethyl-p-phenylenediamine and 2,2'-azinobis-(3-ethyl-benzthiazoline- 6-sulphonate) (the oxidizing radicals). These radicals mainly (≥ 85 % ) disproportionate. one of the products being formaldehyde
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Nakashima, Nobuaki, i Keitaro Yoshihara. "Oscillator Strengths of the Ultraviolet Bands of Hot and Relaxed Methallyl, Allyl, and Methyl Radicals". Laser Chemistry 7, nr 2-4 (1.01.1987): 177–96. http://dx.doi.org/10.1155/lc.7.177.
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Absorption spectra of methallyl, allyl, and methyl radicals were measured in the ArF laser flash photolysis of halogenated methanes and olefins, and 2-methyl-1-butene. Broad absorption spectra were detected immediately after excitation, indicating that the radicals carried high internal energy (called “hot” radicals here). The spectra were sharpened with time due to collisions with foreign gases and finally reached equilibrium (spectra in relaxed states). The oscillator strengths (f) of methallyl and allyl radicals were found to remain about the same for hot and relaxed states. The values (f) in the relaxed states were determined with errors of ±10% to be 0.14 for the methallyl radical, 0.26 for the allyl radical, and 1.57 × 10−2 (including the partition function) for the methyl radical. The molar extinction coefficients of the allylic radicals were 1.4–1.8 times as great as ones previously reported. Rate constants of collisional relaxation by nitrogen were discussed for seven hot radicals and molecules. Larger species gave greater rate constants. The hot methyl radical relaxed with a rate constant of 1.0 × 107s−1 in the presence of 760 Torr of nitrogen, while for the trimethylallyl radical it was 20 times as great as that of the methyl radical.
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Ho, Connie Suk-Han, Ting-Ting Ng i Wing-Kin Ng. "A “Radical” Approach to Reading Development in Chinese: The Role of Semantic Radicals and Phonetic Radicals". Journal of Literacy Research 35, nr 3 (wrzesień 2003): 849–78. http://dx.doi.org/10.1207/s15548430jlr3503_3.
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Two studies investigating the significance of radical knowledge in Chinese reading development are reported in this paper. Study 1 examined the semantic radical knowledge of 20 Grade 1, 20 Grade 3, and 20 Grade 5 Chinese children in Hong Kong. It was found that various types of semantic radical knowledge, including the position and semantic category of semantic radicals, correlated significantly with Chinese word reading and sentence comprehension. Study 2 examined phonetic radical knowledge with another three groups of 20 Chinese children in Grades 1, 3, and 5 respectively. It was found that various measures of phonetic radical knowledge, including the function and sound value of phonetic radicals, correlated significantly with Chinese word reading. These studies found that, developmentally, the children started acquiring the knowledge of character structure, position, semantic category, and sound value of radicals from about Grade 1. However, they did not understand that the function of semantic radicals is to provide meaning cues in reading until Grade 3. The authors concluded that the radical is an important orthographic processing unit in reading development in Chinese.
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Zhang, Sheng Song, Yu Li i Cao Hu. "Numerical Study on the Initial Formation of the Radial Sand Ridges". Applied Mechanics and Materials 641-642 (wrzesień 2014): 222–25. http://dx.doi.org/10.4028/www.scientific.net/amm.641-642.222.
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The radial sand ridges located in the southern Yellow Sea off the Jiangsu coast, are unique sand ridges. They are characterized by radical current field and radical arrangement. The formation and maintenance mechanism of the radial sand ridges have always been a focus of attention of scholars for a long time. The formation is related to the unique convergent-divergent tidal currents. In this paper, a numerical model is constructed to answer the two following questions. Firstly, can the radial sand ridges be formed with radical tidal current field? Secondly, can this be simulated by a numerical model? The radial tidal current can shape the radial sand ridges. Numerical simulations show that the radial sand ridges can be formed on present radical tidal current field and the formation and evolution of the radial sand ridges can be simulated by a numerical model.
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Schepp, N. P., i Y. Rodríguez-Evora. "Generation and reactivity of the radical cations of coniferyl alcohol and isoeugenol in solution". Canadian Journal of Chemistry 81, nr 6 (1.06.2003): 799–806. http://dx.doi.org/10.1139/v03-075.
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Nanosecond laser flash photolysis of coniferyl alcohol and isoeugenol in acetonitrile leads to the formation of transient species that are identified as the corresponding radical cations. These radical cations decay with rate constants of ca. 1 × 106 s1 in dry acetonitrile. Both radical cations react rapidly with hydroxylic solvents like water and alcohols to give 4-vinylphenoxyl radicals, indicating that these reagents behave as bases rather than nucleophiles. In addition, anionic reagents (acetate, cyanide, and chloride) react rapidly with the radical cations with second-order rate constants that are close to diffusion controlled. The main products generated in the presence of the anionic reagents are again the 4-vinylphenoxyl radicals, suggesting that these reagents also behave as bases. The lifetime of the radical cations in acidic acetonitrile was found to increase dramatically due to a shift in the radical cation vinyl phenoxyl radical acidbase equilibrium to the side of the radical cation. An estimate of the pKa of the radical cation in acetonitrile of 4.0 was obtained from the data.Key words: radical cations, laser flash photolysis, lignan, vinylphenols.
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Wang, Chang-Ling, Jie Wang, Ji-Kang Jin, Bin Li, Yee Lin Phang, Feng-Lian Zhang, Tian Ye i in. "Boryl radical catalysis enables asymmetric radical cycloisomerization reactions". Science 382, nr 6674 (grudzień 2023): 1056–65. http://dx.doi.org/10.1126/science.adg1322.
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The development of functionally distinct catalysts for enantioselective synthesis is a prominent yet challenging goal of synthetic chemistry. In this work, we report a family of chiral N -heterocyclic carbene (NHC)–ligated boryl radicals as catalysts that enable catalytic asymmetric radical cycloisomerization reactions. The radical catalysts can be generated from easily prepared NHC-borane complexes, and the broad availability of the chiral NHC component provides substantial benefits for stereochemical control. Mechanistic studies support a catalytic cycle comprising a sequence of boryl radical addition, hydrogen atom transfer, cyclization, and elimination of the boryl radical catalyst, wherein the chiral NHC subunit determines the enantioselectivity of the radical cyclization. This catalysis allows asymmetric construction of valuable chiral heterocyclic products from simple starting materials.
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Heidbrink, J. L., F. S. Amegayibor i H. I. Kenttämaa. "Gas-phase radical-radical recombination reactions of nitroxides with substituted phenyl radicals". International Journal of Chemical Kinetics 36, nr 4 (3.02.2004): 216–29. http://dx.doi.org/10.1002/kin.10189.
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Ma, Xiaoming, Qiang Zhang i Wei Zhang. "Remote Radical 1,3-, 1,4-, 1,5-, 1,6- and 1,7-Difunctionalization Reactions". Molecules 28, nr 7 (28.03.2023): 3027. http://dx.doi.org/10.3390/molecules28073027.
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Radical transformations are powerful in organic synthesis for the construction of molecular scaffolds and introduction of functional groups. In radical difunctionalization reactions, the radicals in the first functionalized intermediates can be relocated through resonance, hydrogen atom or group transfer, and ring opening. The resulting radical intermediates can undertake the following paths for the second functionalization: (1) couple with other radical groups, (2) oxidize to cations and then react with nucleophiles, (3) reduce to anions and then react with electrophiles, (4) couple with metal-complexes. The rearrangements of radicals provide the opportunity for the synthesis of 1,3-, 1,4-, 1,5-, 1,6-, and 1,7-difunctionalization products. Multiple ways to initiate the radical reaction coupling with intermediate radical rearrangements make the radical reactions good for difunctionalization at the remote positions. These reactions offer the advantages of synthetic efficiency, operation simplicity, and product diversity.
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Seol, Youbin, Minsu Choi, Hongyoung Chang i Shinjae You. "Study on OH Radical Production Depending on the Pulse Characteristics in an Atmospheric-Pressure Nanosecond-Pulsed Plasma Jet". Materials 16, nr 10 (19.05.2023): 3846. http://dx.doi.org/10.3390/ma16103846.
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Hydroxyl radicals (OH) play a crucial role in plasma-bio applications. As pulsed plasma operation is preferred, and even expanded to the nanosecond range, it is essential to study the relationship between OH radical production and pulse characteristics. In this study, we use optical emission spectroscopy to investigate OH radical production with nanosecond pulse characteristics. The experimental results reveal that longer pulses generate more OH radicals. To confirm the effect of pulse properties on OH radical generation, we conduct computational chemical simulations, focusing on two types of pulse properties: pulse instant power and pulse width. The simulation results show that, similar to the experimental results, longer pulses generate more OH radicals. In the nanosecond range, reaction time is critical for OH radical generation. In terms of chemical aspects, N2 metastable species mainly contribute to OH radical generation. It is a unique behavior observed in nanosecond range pulsed operation. Furthermore, humidity can turn over the tendency of OH radical production in nanosecond pulses. In a humid condition, shorter pulses are advantageous for generating OH radicals. Electrons play key roles in this condition and high instant power contributes to them.
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ÇELİKÇİ, Handan. "Radikal Hayalciler/Kadınlar Radical Daydreamers/Women". Kadin ve Demokrasi Dernegi 6, nr 2 (13.01.2021): 343–48. http://dx.doi.org/10.21798/kadem.2022.107.
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Angerhofer, Alexander, i Robert Bittl. "Radicals and Radical Pairs in Photosynthesis". Photochemistry and Photobiology 63, nr 1 (styczeń 1996): 11–38. http://dx.doi.org/10.1111/j.1751-1097.1996.tb02989.x.
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Rhim, Tae-Jin, Hee-Sun Jeong, Young-Jin Kim, Doo-Young Kim, Young-Ju Han, Hae-Yon Kwon i Ki-Rok Kwon. "A study on the comparison of antioxidant effects among cultivated ginseng, and cultivated wild ginseng extracts -Using the measurement of superoxide and hydroxy radical scavenging activities-". Journal of Korean Institute of Herbal Acupuncture 12, nr 2 (30.06.2009): 7–12. http://dx.doi.org/10.3831/kpi.2009.12.2.007.
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Simons, Jack. "Do not forget the Rydberg orbitals". Journal of Chemical Physics 156, nr 10 (14.03.2022): 100901. http://dx.doi.org/10.1063/5.0084574.
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Within any molecule or cluster containing one or more positively charged sites, families of Rydberg orbitals exist. Free electrons can attach directly, and anionic reagents with low electron binding energy can transfer an electron into one of these orbitals to form a neutral Rydberg radical. The possibilities that such a radical could form a covalent bond either to another Rydberg radical or to a radical holding its electron in a conventional valence orbital are considered. This Perspective overviews two roles that Rydberg radicals can play, both of which have important chemical consequences. Attachment of an electron into excited Rydberg orbitals is followed by rapid (∼10−6 s) relaxation into the lowest-energy Rydberg orbital to form the ground state radical. Although the excited Rydberg species are stable with respect to fragmentation, the ground-state species is usually quite fragile and undergoes homolytic bond cleavage (e.g., –R2NH dissociates into –R2N + H or into –RNH + R) by overcoming a very small barrier on its potential energy surface, thus generating reactive radicals (H or R). Here, it is shown that as a result of this fragility, any covalent bonds formed by Rydberg radicals are weak and the molecules they form are susceptible to exothermic fragmentations that involve quite small activation barriers. Another role played by Rydberg species arises when the Coulomb potentials provided by the (one or more) positive site(s) in the molecule stabilize low-energy anti-bonding orbitals (e.g., σ* orbitals of weak σ bonds or low-lying π* orbitals) to the extent that electron attachment into these Coulomb-stabilized orbitals is rendered exothermic. In such cases, the overlap of the Rydberg orbitals on the positive site(s) with the σ* or π* orbitals allows either a free electron or a weakly bound electron to an anionic reagent that is attracted toward the positive site by its Coulomb force to be guided/transferred into the σ* or π* orbital instead. After attaching to such an anti-bonding orbital, bond cleavage occurs again, generating reactive radical species. Because of the large radial extent of Rydberg orbitals, this class of bond cleavage events can occur quite distant from the positively charged group. In this Perspective, several examples of both types of phenomena are given for illustrative purposes.
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Haire, D. Larry, Yashige Kotake i Edward G. Janzen. "An EPR/ENDOR study of aminoxyls (nitroxides) capable of intramolecular bonding: hydroxyalkyl radical spin adducts of nitrones". Canadian Journal of Chemistry 66, nr 8 (1.08.1988): 1901–11. http://dx.doi.org/10.1139/v88-307.
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A comparison of the effect of solvent and 13C labeling (of the radical addend) on the EPR (electron paramagnetic resonance) spectra of hydroxyalkyl vs. alkyl radical adducts of α-phenyl-N-tert-butyl nitrone (PBN) and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) has been investigated. The solution ENDOR spectra in toluene and in ethanol are the first examples studied of aminoxyls with hydroxyl substituents in close proximity to the free radical centre. Diastereomeric mixtures of hydroxyalkyl radical adducts are clearly resolved by ENDOR spectroscopy. Conformations of these radicals have been assigned based on the 1H and 13C hyperfine splittings (HFS's) and by differential optimum ENDOR temperatures. Definitive assignments of carbon-centered radical adducts of DMPO and PBN are shown to be feasible by monitoring the β-13C HFS's of the radical addend. Long-range γ-H HFS's from the added radical group can be observed when the deuterated spin trap PBN-d14 is used. The production of 13C labeled hydroxyalkyl adducts of nitrones (e.g., DMPO–13CH2OH, from the reaction of hydroxyl radicals with added 13CH3OH) is shown to be useful as an improved EPR spectroscopic method for the verification of the presence of hydroxyl radicals.
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Koshiishi, Ichiro, Kazunori Tsuchida, Tokuko Takajo i Makiko Komatsu. "Radical scavenger can scavenge lipid allyl radicals complexed with lipoxygenase at lower oxygen content". Biochemical Journal 395, nr 2 (28.03.2006): 303–9. http://dx.doi.org/10.1042/bj20051595.
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Lipoxygenases have been proposed to be a possible factor that is responsible for the pathology of certain diseases, including ischaemic injury. In the peroxidation process of linoleic acid by lipoxygenase, the E,Z-linoleate allyl radical–lipoxygenase complex seems to be generated as an intermediate. In the present study, we evaluated whether E,Z-linoleate allyl radicals on the enzyme are scavenged by radical scavengers. Linoleic acid, the content of which was greater than the dissolved oxygen content, was treated with soya bean lipoxygenase-1 (ferric form) in the presence of radical scavenger, CmP (3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-N-oxyl). The reaction rate between oxygen and lipid allyl radical is comparatively faster than that between CmP and lipid allyl radical. Therefore a reaction between linoleate allyl radical and CmP was not observed while the dioxygenation of linoleic acid was ongoing. After the dissolved oxygen was depleted, CmP stoichiometrically trapped linoleate-allyl radicals. Accompanied by this one-electron redox reaction, the resulting ferrous lipoxygenase was re-oxidized to the ferric form by hydroperoxylinoleate. Through the adduct assay via LC (liquid chromatography)–MS/MS (tandem MS), four E,Z-linoleate allyl radical–CmP adducts corresponding to regio- and diastereo-isomers were detected in the linoleate/lipoxygenase system, whereas E,E-linoleate allyl radical–CmP adducts were not detected at all. If E,Z-linoleate allyl radical is liberated from the enzyme, the E/Z-isomer has to reach equilibrium with the thermodynamically favoured E/E-isomer. These data suggested that the E,Z-linoleate allyl radicals were not liberated from the active site of lipoxygenase before being trapped by CmP. Consequently, we concluded that the lipid allyl radicals complexed with lipoxygenase could be scavenged by radical scavengers at lower oxygen content.
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Luo, Jie, Xiao-Fan Rong, Yu-Yuan Ye, Wen-Zhen Li, Xiao-Qiang Wang i Wenjing Wang. "Research Progress on Triarylmethyl Radical-Based High-Efficiency OLED". Molecules 27, nr 5 (1.03.2022): 1632. http://dx.doi.org/10.3390/molecules27051632.
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Perchlorotrityl radical (PTM), tris (2,4,6-trichlorophenyl) methyl radical (TTM), (3,5-dichloro-4-pyridyl) bis (2,4,6 trichlorophenyl) methyl radical (PyBTM), (N-carbazolyl) bis (2,4,6-trichlorophenyl) methyl radical (CzBTM), and their derivatives are stable organic radicals that exhibit light emissions at room temperature. Since these triarylmethyl radicals have an unpaired electron, their electron spins at the lowest excited state and ground state are both doublets, and the transition from the lowest excited state to the ground state does not pose the problem of a spin-forbidden reaction. When used as OLED layers, these triarylmethyl radicals exhibit unique light-emitting properties, which can increase the theoretical upper limit of the OLED’s internal quantum efficiency (IQE) to 100%. In recent years, research on the luminescent properties of triarylmethyl radicals has attracted increasing attention. In this review, recent developments in these triarylmethyl radicals and their derivatives in OLED devices are introduced.
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Wang, Degui, Heinz-Peter Schuchmann i Clemens von Sonntag. "Phenylalanine: Its ˙OH and SO4˙⁻-Induced Oxidation and Decarboxylation. A Pulse Radiolysis and Product Analysis Study". Zeitschrift für Naturforschung B 48, nr 6 (1.06.1993): 761–70. http://dx.doi.org/10.1515/znb-1993-0610.
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Phenylamine has been oxidized by radiolytically generated hydroxyl and sulfate radicals, the ensuing intermediates and their reactions have been studied by pulse radiolysis and product analysis in the absence and presence of oxidants such as Fe(CN)63- and O2. Upon OH radical attack, hydroxycyclohexadienyl-type radicals are mainly formed while Η-abstraction reactions can be neglected. In the presence of Fe(CN)63- these radicals are for the most part oxidized to the corresponding tyrosines (80%), except for the ipso-OH-adduct radicals (≈ 20%). It is concluded that ˙OH-addition is almost random, but with a slight avoidance of the metaposition relative to the ortho-, para- and ipso-positions. Oxygen adds reversibly to the OH-adduct radicals (kf = 1.8 × 108 dm3 mol-1 s-1, kr = 5.4 × 104 s-1). In this case, tyrosine formation occurs by HO2˙-elimination. However, due to side reactions, tyrosine formation only reaches 52% of the OH radical yield. The tyrosine yield drops to 10% in the absence of an oxidant.Upon SO4˙⁻-attack, decarboxylation becomes a major process (33% of SO4˙⁻) alongside the production of tyrosines (43%). Here, with Fe(CN)63- as the oxidant the formation of p-Tyr (18.5%) and m-Tyr (16.5%) is preferred over o-Tyr formation (8.5%). It is believed that in analogy to other systems a radical cation is formed immediately upon SO4˙⁻-attack which either reacts with water under the formation of hydroxycyclohexadienyl-type (“OH-adduct”) radicals, or decarboxylates after intramolecular electron transfer. The radical cation can also arise indirectly through H+-catalysed water elimination from the ˙OH-adduct radicals. At pH 2 and a dose rate of 0.0046 Gy s-1 CO2 formation matches the OH radical yield when ˙OH is the attacking radical. Below pH 2, G(CO2) decreases with falling pH. This indicates the occurrence of another, unimolecular, pathway under these conditions competing effectively with decarboxylation. This appears to be a relatively slow deprotonation reaction of the carboxylprotonated phenylalanine radical cation which gives rise to the benzyl-type radical.
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Brown, CE, AG Neville, DM Rayner, KU Ingold i J. Lusztyk. "Kinetic and Spectroscopic Studies on Acyl Radicals in Solution by Time-Resolved Infrared Spectroscopy". Australian Journal of Chemistry 48, nr 2 (1995): 363. http://dx.doi.org/10.1071/ch9950363.
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A number of acyl radicals, RĊ=O, have been generated in hexane or di -t-butyl peroxide as solvent at room temperature by 308 nm laser flash photolysis, and their spectroscopic and kinetic properties have been examined by time-resolved infrared spectroscopy. The C=O stretching frequencies for the RĊ=O radicals are found to be higher than those of the corresponding aldehydes, RCHO, by between 108 and 128 cm-1, an effect attributed to a higher C=O bond order in the radicals. For the RĊ=O radicals some typical values of vC =O are: CH3Ċ=O, 1864 cm-1; (CH3)3CĊ=O, 1848 cm-1; and C6H5Ċ=O, 1828 cm-1, while the corresponding acylperoxyl radicals, RC(O)OO, formed by reaction with oxygen have vC =O values of 1838, 1840 and 1820 cm-1, respectively. The acyl radicals exhibit a reactivity towards a variety of substrates that is roughly comparable to that of simple alkyl radicals. For reactions of the benzoyl radical some typical rate constants/M-1 s-1 are: CCl4, 6.0x104; C6H5SH, 4.8×107; CCl3Br, 2.2×108; Tempo, 1.1×109; and oxygen, 1.8×109. Alkanoyl radicals have a rather similar reactivity to benzoyl. The propanoyl radical reacts with tributyltin deuteride with a rate constant of 3×105 M-1s-1. The hex-5-enoyl radical undergoes a 5-exo-trig cyclization to form the 2-oxocyclopentylmethyl radical with a rate constant of 2.2×105 s-1, a value which is almost identical to that for cyclization of the hex-5-enyl radical. It is hoped that our kinetic data will prove useful in the planning of organic synthetic strategies which involve acyl radical chemistry.
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Xu, Fei, Wanni Yu, Rui Gao, Qin Zhou, Qingzhu Zhang i Wenxing Wang. "Dioxin Formations from the Radical/Radical Cross-Condensation of Phenoxy Radicals with 2-Chlorophenoxy Radicals and 2,4,6-Trichlorophenoxy Radicals". Environmental Science & Technology 44, nr 17 (wrzesień 2010): 6745–51. http://dx.doi.org/10.1021/es101794v.
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Rao, Ashwathanarayana. "STUDY ON ANTIOXIDANT AND CYTOTOXIC PROPERTIES OF OLEA DIOICA ROXB. CRUDE EXTRACT AND ITS PURE COMPOUND COLLECTED FROM WESTERN GHATS, KARNATAKA, INDIA." Asian Journal of Pharmaceutical and Clinical Research 10, nr 2 (1.02.2017): 356. http://dx.doi.org/10.22159/ajpcr.2017.v10i2.15727.
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Introduction: Olea dioica Roxb. an important medicinal tree plants used by local siddha tribes, belongs to the family Oleaceae. The parts such asleaves, bark, root, and fruits used in the traditional medicine to cure skin diseases, rheumatism, fever, and cancer.Objectives: The anti-oxidant experiment by metal chelating activity, superoxide radicals, hydroxyl radical, 2,2-diphenyl-2-picrylhydrazyl radicals,2,2-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid radical scavenging assays with in vitro cytotoxicity was tested using trypan blue dye exclusiontechnique and 3-(4, 5 dimethylthiazole-2yl)-2, 5-diphenyltetrazolium bromide assay was conducted.Results: Anti-oxidant experiments revealed that the bark ethanolic extract of the O. dioica plant parts has excellent radical scavenging activity and itsextracted pure compound, Benzene ethanol, 4-hydroxy-alcohol, showed excellent radical scavenging activity higher than the standards used. In vitrocytotoxicity experiments revealed that bark ethanolic extract has excellent cytotoxicity activity and its pure compound benzene-ethanol, 4-hydroxyalcoholalso showed excellentactivitywhichis comparablewith the standardcurcumin.Conclusion: O. dioica bark could be exploited as a valuable source of antioxidant and cytotoxic agent for pharmaceutical industry.Keywords: Olea dioica Roxb, Metal chelating, Superoxide radicals, Hydroxyl radical, 2,2-diphenyl-2-picrylhydrazyl radicals, 2,2-azinobis(3-ethylbenzothiazoline)-6-sulfonic acid radical scavenging,Trypan blue, 3-(4,5dimethylthiazole-2yl)-2,5-diphenyltetrazolium bromide assay, Benzeneethanol, 4-hydroxy-alcohol.
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Godloza, L., N. J. Groenewald i W. A. Olivier. "Near-Ring Radicals and Class Pairs". Algebra Colloquium 12, nr 01 (marzec 2005): 101–12. http://dx.doi.org/10.1142/s100538670500009x.
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For near-ring ideal mappings ρ1 and ρ2, we investigate radical theoretical properties of and the relationship among the class pairs (ρ1: ρ2), [Formula: see text] and (ℛρ2: ℛρ1). Conditions on ρ1 and ρ2 are given for a general class pair to form a radical class of various types. These types include the Plotkin and KA-radical varieties. A number of examples are shown to motivate the suitability of the theory of Hoehnke-radicals over KA-radicals when radical pairs of near-rings are studied. In particular, it is shown that [Formula: see text] forms a KA-radical class, where [Formula: see text] denotes the class of completely prime near-rings and [Formula: see text] the class of 3-prime near-rings. This gives another near-ring generalization of the 2-primal ring concept. The theory of radical pairs are also used to show that in general the class of 3-semiprime near-rings is not the semisimple class of the 3-prime radical.
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TUMURBAT, S., i H. FRANCE-JACKSON. "ON PRIME-LIKE RADICALS". Bulletin of the Australian Mathematical Society 82, nr 1 (2.03.2010): 113–19. http://dx.doi.org/10.1017/s0004972709001129.
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AbstractA radical γ is prime-like if, for every prime ring A, the polynomial ring A[x] is γ-semisimple. In this paper, we study properties of prime-like radicals. In particular, we give necessary and sufficient conditions for a radical γ containing the prime radical β to be prime-like. This allows us to easily find distinct special radicals that coincide on simple rings and on polynomial rings, which answers a question put by Ferrero. It also allows us to reformulate a long-standing open problem of Gardner in terms of prime-like radicals.