Radicals and their reactions

Ebook "Free radicals in organic synthesis (Reactivity and structure concepts in organic chemistry, Volume 7)" has a comparatively long history. Before the accep- tance of the quadrivalence of carbon, various attempts were made to prepare trivalent carbon species like methyl and ethyl. Initial investigations involving reaction between alkyl iodides and zinc were thought to be successful but were subsequently branded as failures 2.

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The synthesis of natural products 2-(2,3-dibromo-4,5-dihydroxyphenyl)acetic acid (1) and 2-(2,6-dibromo-3,5- dihydroxyphenyl)acetic acid (2) and as well as their derivatives 25 and 26 were carried out by substitution, hydrolysis and demethylation reactions of the corresponding four benzyl bromides. The antioxidant potentials of benzylic acid-derived bromophenols were, for the first time, appraised by several outstanding bioanalytical methods.

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Some novel 2-(substitutedbenzylthio)-5-((2-(4-substitutedphenyl)-1H -benzo[d]imidazol-1-yl)methyl)-1,3,4- oxadiazoles (5–12) and 2-(2-(4-chlorophenyl)-1H -benzo[d]imidazol-1-yl)-N ′ -(arylmethylene)acetohydrazide derivatives (13–22) were prepared and their in vitro antioxidant properties were investigated by determination of rat liver microsomal NADPH-dependent inhibition of lipid peroxidation (LP) levels and microsomal ethoxyresorufin O-deethylase (EROD) activity. Compound 18 was found to be the most active compound with 100% inhibition on LP level and 92% inhibition on EROD.

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Hydroxybenzoic acids (HBAs) and their anions play an important role in the food and pharmaceutical industries because of their antioxidant activity. In this study, we examined the mechanisms of the free radical scavenging action of HBAs and their anions using density functional theory (DFT) methods. Reaction enthalpies related to the mechanisms of free radical scavenging by the investigated species were calculated by DFT methods in water, DMSO, pentylethanoate, and benzene.

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As a starting material, 7-tert-butyldibenzo [b,e] [1,4] dioxine-2,3-dicarbonitrile was prepared by the reaction of 4-tert-butylcatechol with 4,5-dichlorophthalonitrile. Metallophthalocyanine complexes (4–7) were obtained by cyclotetramerization of 7-tert-butyldibenzo [b,e] [1,4] dioxine-2,3-dicarbonitrile. All compounds were characterized by elemental analysis and other spectroscopic methods (IR, UV/Vis, and 1 H NMR). Phthalocyanine compounds remained nonaggregated in tetrahydrofuran at the studied concentration ranges.

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Glutathione reductase (GR, EC 1.8.1.7) is an antioxidant enzyme and is involved in the reducing reaction of oxidized glutathione. Glutathione and reduced glutathione are very crucial for micro- and macroorganisms because of their barrier function against radicals. Therefore, the aim of this article was to purify GR and evaluate the relationship between purified GR and vitamins. GR was purified from bovine liver using 2’,5’-ADP Sepharose 4B column materials. To check the purity of each subunit of the enzyme, SDS-PAGE electrophoresis was performed and each one was 55 kDa.

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Poly(methyl methacrylate) (PMMA) and poly(ethylene glycol) methyl ether (mPEG)-based monotelechelics were quantitatively prepared by copper (I)-catalyzed azide/alkyne cycloaddition (CuAAC) click reactions using azido-terminated polymers and alkyne functional benzodioxinones. The monotelechelic containing dimethyl moities (2,2-dimethyl-5-(prop-2-yn-1-yloxy)-4Hbenzo[d][1,3]dioxin-4-one) was heat-sensitive, whereas the monotelechelic containing diphenyl moieties (2,2-diphenyl-5-(prop-2-yn1-yloxy)-4H-benzo[d][1,3]dioxin-4-one) was UV light sensitive.

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A phthalocyanine (Pc) initiator, tetrakis(2-bromopropyloxyester)ethylthiophthalocyaninatozinc(II) (ZnPcBr), was prepared and successfully applied to atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) for the first time. Bromine end groups of the synthesized Pc took part in the initiation of the MMA chain growth. Polymerization was demonstrated by monomodal molecular weight distribution of the synthesized polymers and their increasing molecular weight behavior with reaction time.

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A novel series of 4-methoxy, and 4,9-dimethoxy-5-substituted furo[2,3-g]-1,2,3-benzoxathiazine-7,7-dioxide derivatives 3a,b, 10a–g and 11a–g were prepared in good yields via the reaction of 4-methoxy (1a) and 4,7-dimethoxy-5-acetyl-6-hydroxybenzofurans (1b) and their a,b-unsaturated keto derivatives 6a–g and 7a–g with chlorosulfonyl isocyanate (CSI). On the other hand, N-chlorosulfonyl carbamate derivatives 4a,b, 12a,b and 13a,b were prepared and allowed to react with piperidine to give the corresponding N-piperidinosulfonyl carbamate derivatives 5a,b, 14a,b and 15a,b, respectively.

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(bq) part 2 book "aguid to mechanism in organic chemistry" has contents: nucleophilic addition to c=o; elimination reactions; carbanions and their reactions; radicals and their reactions; symmetry controlled reactions; linear free energy relationships.

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(BQ) Part 1 of the document Organic chemistry presents the following contents: The basics-bonding and molecular structure; families of carbon compounds-functional groups, intermolecular forces, and infrared (IR) spectroscopy; acids and bases-an introduction to organic reactions and their mechanisms; nomenclature and conformations of alkanes and cycloalkanes; radical reactions;...

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Chapter 4 - The Study of chemical reactions. In this chapter, students will be able to: Propose mechanisms and explain the steps for simple reactions such as free-radical halogenation; draw a reaction-energy diagram, and use it to identify the factors controlling the thermodynamics and kinetics of a reaction; use the mechanism, thermodynamics, and kinetics of a reaction to predict which of several possible products is the major product; identify reactive intermediates and explain their properties.

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Exposure to quartz particles induces a pathological process named silicosis. Alveolar macrophages initiate the disease through their activation, which is the origin of the later dysfunctions. Ascorbic acid is known to selectively dissolve the quartz surface. During the reaction, ascorbic acid progressively disappears and hydroxyl radicals are generated from the quartz surface. These observations may be relevant to mammalian quartz toxicity, as sub-stantial amounts of ascorbic acid are present in the lung epithelium. ...

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After opening a new class of chemical reactions in 1964, reactions in which unpaired electrons of stable radicals were not involved, nitroxide (aminoxyl) radicals became one of the most interesting and rapidly developing area of modern physical chemistry with their application to biophysics, molecular biology, polymer sciences and medicine. Further development of this field depends on new pathways in the nitroxide chemistry, modern methods in EPR spectroscopy and revealing new perspective practical approaches....

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Depending on their structures, polyphenols (e.g. tea polyphenols) could also act by chelating prooxidant transition metal ions such as Fe2+, which are involved in reactions eliciting free radical production, including hydroxyl radicals (OH•) and alkoxyl radicals (RO•) (Dufresne & Farnworth, 2001).

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