- Comparison of Heterogeneous and Homogeneous Electron-Transfer Rates for Some Nitroalkanes and Diketones
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Redox catalysis has been used to investigate the homogeneous electron-transfer reactions between the substrates (nitroalkane or diketone) and the reduced form of the catalyst, which was terephthalonitrile.The substrates were RNO2 (R=Me, Et, i-Pr, and t-Bu) and RC(O)C(O)R (R=Me, Et, and t-Bu).The experiments were conducted in acetonitrile solvent at 298 K with three different electrolytes, R4NClO4 (R=Et, n-Bu, and n-C7H15).The effect of added water and alcohols (methanol, ethanol, and s-butanol) was investigated.Formal potentials and standard heterogeneous electron-transfer rate constants, ks, were also determined.It was found that increasing the size of the cation of the electrolyte resulted in a decrease in ks but did not affect the rate of the homogeneous electron-transfer reactions.The result is interpreted as a decrease in electron-tunneling rate with increasing thickness of a compact layer of adsorbed cations, a double-layer effect that cannot influence the homogeneous reaction.Addition of the hydroxylic solutes, S, caused diminution of both ks and the rate constant of homogeneous electron transfer from the anion radical of the substrate to the catalyst.This result is discussed in terms of two models, viz., complexation or adduct formation between the anion radical and S or increasing solvation energy of the anion radical.
- Evans, Dennis H.,Gilicinski, Andrew G.
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Read Online
- Copper(II) mediated phenol ring nitration by nitrogen dioxide
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Cu(ii) complexes of N2O2 type ligands, L1H2 and L2H2 [L1H2 = 6,6′-(((pyridin-2-ylmethyl)azanediyl)bis(methylene))bis(2,4-di-tert-butylphenol); L2H2 = 2,4-di-tert-butyl-6-(((3-(tert-butyl)-2-hydroxy-5-methylbenzyl)(pyridin-2-yl-methyl)amino)methyl)phenol], have been synthesized. Addition of nitrogen dioxide (NO2) in THF solutions of the complexes resulted in the nitration at the 4-position of a coordinated equatorial phenolate ring of the ligand frameworks. This nitration did not occur at the phenol ring which is axially coordinated to the metal center. Spectroscopic evidence suggests that the reaction proceeds through a phenoxyl radical complex formation.
- Kumar, Vikash,Ghosh, Somnath,Saini, Anoop Kumar,Mobin, Shaikh M.,Mondal, Biplab
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p. 19909 - 19917
(2015/12/01)
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- Silver(I)-Promoted ipso-Nitration of Carboxylic Acids by Nitronium Tetrafluoroborate
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A novel and efficient method for the regioselective nitration of a series of aliphatic and aromatic carboxylic acids to their corresponding nitro compounds using nitronium tetrafluoroborate and silver carbonate in dimethylacetamide has been described. This transformation is believed to proceed via the alkyl-silver or aryl-silver intermediate, which subsequently reacts with the nitronium ion to form nitro substances. Mild reaction conditions, tolerant of a broad range of functional groups, and formation of only the ipso-nitrated products are the key features of this methodology when compared to known methods for syntheses of nitroalkyls and nitroarenes.
- Natarajan, Palani,Chaudhary, Renu,Venugopalan, Paloth
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p. 10498 - 10504
(2015/11/18)
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- HYDROCARBON FEED FLEXIBLE HIGH PRESSURE NITRATION PLANT DESIGN
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Disclosed is an apparatus for synthesizing nitroalkanes by reaction of a hydrocarbon feedstock with aqueous nitric acid. The apparatus may be designed such that it can synthesize more than one nitroalkane using the same equipment.
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Page/Page column 21-26
(2011/07/09)
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- NITRATED HYDROCARBONS, DERIVATIVES, AND PROCESSES FOR THEIR MANUFACTURE
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Provided is a process for the formation of nitrated compounds by the nitration of hydrocarbon compounds with dilute nitric acid. Also provided are processes for preparing industrially useful downstream derivatives of the nitrated compounds, as well as novel nitrated compounds and derivatives, and methods of using the derivatives in various applications.
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Page/Page column 27-29; 33
(2009/12/02)
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- Spin trapping of Au-H intermediate in the alcohol oxidation by supportedand unsupported gold catalysts
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Electron paramagnetic resonance (EPR) spectroscopy and spin trapping were used to explore the mechanism of alcohol oxidation over gold catalysts. Reaction of secondary alcohols with supported and unsupported gold catalysts (e.g., Au/CeO2, polymer-Incarcerated Au nanoparticles,PPh 3-protected Au nanoparticles) In the presence of spin tr aps led to the formation of a hydrogen spin adduct. Using Isotope labeling, we confirmed that the hydrogen In the spin adduct originates from the cleavage of the C-H bond In the alcohol molecule. The formation of thehydrogen spin adduct most likely results from the abstraction of hydrog en from the Au surface by a spin trap. These results thus strongly suggest Intermediate formation of Au-H species during alcohol oxidation. The role of oxygen In this mechanism Is to restore the catalytic activity rather than oxidize alcohol. This was further confirmed by carrying out gold-catalyzed alcohol oxidation In the absence of oxygen, with nitroxidesas hydrogen abstractors. The support (e.g., metal oxides) can activate oxygen and act as an H abstractor from the gold surface and hence lead t o a faster recovery of the activity. Peroxyl radicals were also observedduring alcohol oxidation, consistent with a free-radical autoxidation m echanism. However, this mechanism Is likely to be a minor side reaction,which does not lead to the formation of an appreciable amount of oxidat ion products.
- Conte, Marco,Miyamura, Hiroyuki,Kobayashi, Shu,Chechik, Victor
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supporting information; experimental part
p. 7189 - 7196
(2009/09/30)
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- Oxidation of azides by the HOF·CH3CN: A novel synthesis of nitro compounds
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The HOF·CH3CN complex, readily prepared by passing F 2 through aqueous acetonitrile, is an exceptionally efficient oxygen transfer agent. It is unique in its capacity to oxidize various azides into the corresponding nitro derivatives. This method requires short reactions times and room temperature or below, and the desired nitro compounds were usually isolated in very good yields. The respective nitroso derivatives are believed to be the intermediates in this reaction. Functional groups such as aromatic rings, ketones, nitriles, halides, alcohols, and esters are tolerated. Sulfides react with HOF·CH3CN usually at the same rate as azides. Amines and olefins, however, react faster, so they have to be protected first. Nitro derivatives with various oxygen isotopes can be made using the labeled H 18OF·CH3CN. In the case of chiral azides the stereochemistry around the nitrogen-bonded carbons is retained.
- Carmeli, Mira,Rozen, Shlomo
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p. 4585 - 4589
(2007/10/03)
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- Aqueous biphasic oxidation: A water-soluble polyoxometalate catalyst for selective oxidation of various functional groups with hydrogen peroxide
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A "sandwich" type polyoxometalate, Na12[(WZn 3(H2O)2][(ZnW9O34) 2], was used as an oxidation catalyst in aqueous biphasic reaction media to effect oxidation of alcohols, diols, pyridine derivatives, amines and aniline derivatives with hydrogen peroxide. The catalyst was shown by 183W NMR to be stable in aqueous solutions in the presence of H 2O2 and showed only minimal non-productive decomposition of the oxidant. Secondary alcohols were selectively oxidized to ketones, while primary alcohols tended to be oxidized to the corresponding carboxylic acids, although secondary alcohols were selectively oxidized in the presence of primary alcohols. Vicinal diols yielded carbon-carbon bond cleavage products in very high yields. Pyridine derivatives were oxidized to the respective TV-oxides, but strongly electron-withdrawing moieties inhibited the oxidation reaction. Primary amines were oxidized to the oximes, but significantly hydrolyzed in situ. Aniline derivatives were oxidized to the corresponding azoxy or nitro products depending on the substitution pattern in the aromatic ring. Catalyst recovery and recycle was demonstrated.
- Sloboda-Rozner, Dorit,Witte, Peter,Alsters, Paul L.,Neumann, Ronny
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p. 339 - 345
(2007/10/03)
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- An efficient nitration of light alkanes and the alkyl side-chain of aromatic compounds with nitrogen dioxide and nitric acid catalyzed by N-hydroxyphthalimide
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Nitration of light alkanes and the alkyl side-chain of aromatic compounds with NO2 and HNO3 was successfully achieved by the use of N-hydroxyphthalimide (NHPI) as a catalyst under relatively mild conditions. For example, the nitration of propane with NO2 catalyzed by NHPI at 100 °C for 14 h gave 2-nitropropane in good yield without formation of 1-nitropropane and cleaved products such as nitroethane and nitromethane. Various aliphatic nitroalkanes, which are difficult to prepare by conventional methods, could be selectively obtained by means of the present methodology by using NHPI as the key catalyst. In addition, the side-chain nitration of alkylbenzenes such as toluene was selectively carried out to lead to α-nitrotoluene without the ring nitration. The present reaction provides an efficient selective method for the nitration of light alkanes and alkylbenzenes, which has been very difficult to carry out so far.
- Nishiwaki, Yoshiki,Sakaguchi, Satoshi,Ishii, Yasutaka
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p. 5663 - 5668
(2007/10/03)
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- Increased intensity of tert-butoxyl radical emission in 4-chloro-2- methylphenoxyacetic acid (MCPA) synthesis
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The important herbicide, 2-methyl-4-chlorophenoxyacetic acid (MCPA) was synthesized by the chlorination of 2-methylphenoxyacetic acid with tert-butyl hypochlorite in the presence of methyl N,N-dimethylglycinate as a catalyst, giving a high yield and regioselectivity. The reaction was investigated using the spin-trapping technique in electron paramagnetic resonance measurement conditions, with nitrosodurene as a spin trap. Increased intensity emission of the tert-butoxyl radical (2.9 times in relation to the starting level) was observed after the catalyst had been introduced into the reaction mixture, indicating a free radical mechanism for the reaction.
- Jezierski, Adam,Zakrzewski, Jerzy,Moszczyski, Wiesaw
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p. 1229 - 1232
(2007/10/03)
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- Kinetic studies of the reaction of some nitrosoalkanes with nitrogen dioxide
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The rates of the oxidation of some nitrosoalkanes (CH3)2C(CH2X)NO by nitrogen dioxide in carbon tetrachloride have been studied by stopped-flow techniques, and have been found to exhibit second order kinetics. Arrhenius parameters have been determined for the cases of X = H, CH3, C(CH3)3, C6H5, NO2, Cl and OCOCH3. Electron withdrawing substituents are found to decrease significantly the rates, which are generally much faster than the corresponding oxidation of nitrosoarenes. The results obtained are discussed with reference to the Hammett σ constants of the substituents X, and the atomic charges at the nitrogen atom as given by the TNDO/2 method, the geometries of the molecules having been optimised by the PM3 semi-empirical method.
- Gowenlock, Brian G.,King, Boyd,Pfab, Josef,Witanowski, Michal
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p. 483 - 485
(2007/10/03)
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- Zirconium-Catalyzed Oxidation of Primary Aliphatic Amines to Nitro Compounds with tert-Butyl Hydroperoxide
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Primary aliphatic amines are oxidized with tert-butyl hydroperoxide to the corresponding nitro compounds in 50-98% yield using Zr(Ot-Bu)4 as the catalyst. The CH-acidic nitro compounds are not epimerized under these reaction conditions.
- Krohn, Karsten,Kuepke, Jochen
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p. 679 - 682
(2007/10/03)
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- Spin trapping chemistry of iminyl free radicals
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The iminyl radicals formed from hydrogen atom abstraction between tert-butoxyl radicals and benzylidene-N-alkyl-or N-arylamines were trapped by 2-methyl-2-nitrosopropane and investigated by EPR spectroscopy. The compounds investigated were benzylidene N-methyl, ethyl, 1-propyl, 1-butyl, 2-methylpropyl, 1-methylethyl, 1-methylpropyl, 1-ethylpropyl, 1-methylbutyl and cyclohexyl derivative and also benzylidene N-phenyl, 4-tolyl, 4-fluorophenyl, 4-methoxyphenyl, 4-chlorophenyl, 4-nitrophenyl and 4-trifluoromethylphenyl derivatives. In every case the iminyl nitroxide (aminoxyl) was produced in benzene at room temperature. The nitrogen hyperfine splitting constants were in the ranges 3.39-3.56 and 9.68-9.77 G for the iminyl and nitroxyl nitrogens, respectively, for the benzylidene-N-alkylamines and 3.60-3.77 and 8.45-9.15 G for the iminyl and nitroxyl nitrogens, respectively, for the benzylidene-N-arylamines. Very little evidence was found for hydrogen atom abstraction from the alkyl groups attached to the imine function. The absolute rate constant for hydrogen atom abstraction of the iminyl hydrogen was estimated to be 1.2 × 104 M-1 s-1 based on competitive experiments with addition of tert-butoxyl radicals to 2-methyl-2-nitrosopropane (1.5 × 106 M-1 s-1). This value is considerably slower than that for benzaldehyde (2.4 × 107 M-1 s-1).
- Janzen, Edward G.,Nutter, Dale E.
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p. 131 - 140
(2007/10/03)
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- Oxidation of organonitrogen compounds by the methyltrioxorhenium-hydrogen peroxide system
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Methyltrioxorhenium catalyzes the reaction of hydrogen peroxide with organonitrogen compounds. The reactions are facile and high yield at room temperature of below. The observed chemistry is similar to that previously described by us using dimethyldioxirane as the oxidant.
- Murray, Robert W.,Iyanar, Kaliappan,Chen, Jianxin,Wearing, James T.
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p. 805 - 808
(2007/10/03)
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- Spin trap nitronyl hindered phenols
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The invention is the use of nitronyl substituted hindered phenols as antioxidants in therapeutic applications. In the preferred embodiment the compositions have the general formula: STR1 Wherein R1 is hydrogen, an alkyl or an aryl and R2 is an alkyl or an aryl; R3 is an alkyl; and R4 is an alkyl. Further, the invention relates to novel compositions useful as antioxidants. The novel compounds include: 2,6-di-tert-butyl-4-(N-tert-octyl)nitronyl phenol (DBONP); 2,6-dimethyl-4-(N-tert-octyl)nitronyl phenol (DMONP); N-tert-octyl-C-phenyl nitrone (OPN).
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- INTERACTION OF ALKYLIDENE CARBENES WITH NITROSO COMPOUNDS
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The reaction of an alkylidenecarbene with 2-methyl-2-nitrosopropane results in various amides via the intermediacy of keteneimine N-oxide and aziridinone.
- Stang, Peter J.,Anderson, Gary H.
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p. 329 - 332
(2007/10/02)
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- Action d'un Tetrafluoroborate d'Oxaziridinium sur les Amines et les Imines
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The Oxaziridinium salt 1 derived from dihydroisoquinolin is an oxygen transfer reagent to primary amines leading to nitrosoderivatives (if R = Alkyl) or nitro compounds (if R = Aryl), to tertiary amines leading to N-oxides, and to secondary amines and imines leading to the corresponding nitrone.
- Hanquet, Gilles,Lusinchi, Xavier
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p. 12185 - 12200
(2007/10/02)
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- Thermal Decomposition of Nitrate Esters
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Rates of thermal decomposition and solvent rate effects have been measured for a series of nitrate esters.The alkoxy radicals formed by homolysis together with some of their further degradation products have been stabilized by hydrogen donation.Internal and external return of nitrogen dioxide have been demonstrated by solvent cage effects and isotope exchange.Radical-stabilizing substituents favor β-scission.Dinitrates in a 1,5 relationship behave as isolated mononitrates.Dinitrates in a 1,3 or 1,4 relationship exhibit intramolecular reactions.Tertiary nitrate esters in diethyl ether undergo elimination rather than homolysis.
- Hiskey , Michael A.,Brower, Kay R.,Oxley, Jimmie C.
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p. 3955 - 3960
(2007/10/02)
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- Synthesis of Functionalized Acyclic Nitrone Spin Traps
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Four new spin traps with functionalized acyclic nitrone stuctures, EtCH(CH2CH2CO2Et)CH=N(O)CMe3 (3), EtCH(CH2CH2CH2OH)CH=N(O)CMe3 (4), EtCH(CH2CH2CN)CH=N(O)CMe3 (6), EtCH(CH2CH2CO2H)CH=N(O)CMe3 (10), were prepared and characterized by infrared spectrometry, mass spectrometry and 1H NMR. - keywords: Enamine Alkylation, Functionalized Aldehyde, Acyclic Nitrone, Spin Trap, Nitroxide
- Zhang, Yongkang,Xu, Guangzhi
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p. 1475 - 1478
(2007/10/02)
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- Oxidation of Amines with 2-Sulfonyloxaziridines (Davis' Reagents)
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2-(Phenylsulfonyl)-3-aryloxaziridines (Davis' Reagents) react rapidly with amines that are more basic than pyridine to give products that are dependent upon the structure of the amine.Tertiary aliphatic amines are oxidized to the corresponding N-oxides in high yields, while secondary aliphatic amines give the N,N-disubstituted hydroxylamines and corresponding nitrones in variable, stoichiometrically dependent ratios.Primary aliphatic amines give 10-35percent yields of nitroso compounds and 50-65percent yields of N-arylideneamines formed by the transimination reaction of the amine with the N-arylidenebenzenesulfonamide generated following oxygen transfer from the 2-(phenylsulfonyl)-3-aryloxaziridine.
- Zajac, Walter W.,Walters, Thomas R.,Darcy, Michael G.
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p. 5856 - 5860
(2007/10/02)
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- Transition Metal Porphyrins as Catalysts in the Oxidation of Nitroso Compounds
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Iron(III) and manganese(III) porphyrins are found to be very effective catalysts for the oxidation of nitroso to nitro compounds, even at -78 deg C.
- Joergensen, Karl Anker
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p. 1405 - 1406
(2007/10/02)
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- A NEW SYNTHESIS OF NITRO COMPOUNDS USING DIMETHYLDIOXIRANE
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Dimethyldioxirane oxidizes primary amines to nitro compounds in a facile, mild, high yield process.
- Murray, Robert W.,Jeyaraman, Ramasubbu,Mohan, Lily
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p. 2335 - 2336
(2007/10/02)
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- THE REACTION OF CARBANIONS WITH TERT-BUTYL RADICALS
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The SRNl free radical chain reaction of Me3CHgCl with nitronate -O2N=C(R1)(R2)> and phenone enolate -)=C(R1)(R2)> anions yields the C-alkylation products 1)(R2)NO2, PhCOC(R1)(R2)CMe3>.Competitive reactions between pairs of anions demonstrate that as the basicity of the anion increases the reactivity toward Me3Cat first increases and then decreases.An inverted reactivity order is also observed with phenylacetonitrile anions.In early transition state reactions, the nucleophilic character of the tert-butyl radical apparently controls the reactivity by virtue of a transition state involving transfer of the electron from radical to the LUMO of the resonance stabilized anion.
- Russell, Glen A.,Khanna, Rajive K.
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p. 4133 - 4146
(2007/10/02)
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- Kinetics and Mechanism of the C-Alkylation of Nitroalkane Anions by 1-Alkyl-2,4,6-triphenylpyridiniums: A Nonchain Reaction with Radicaloid Characteristics
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The C-alkylation of 2-nitropropanide by N-substituted pyridiniums is first order in each reactant in Me2SO.The effect on the rate of temperature , N substituent, leaving group, and nucleophile was studied quantitatively.Overall, the evidence excludes an SN2 displacement and suggests that the reactions proceed by a free radical nonchain mechanism.
- Katritzky, Alan R.,Kashmiri, M. Akram,Ville, George Z. de,Patel, Ranjan C.
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- Methyl Radical Addition to Nitroalkane aci-Anions in Aqueous Solution: Rate Constants and Optical Absorption Spectra
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Absolute rate constants have been measured for the .CH3 radical addition to the aci-anions of nitromethane, nitroethane, 1-nitropropane, and 2-nitropropane.The respective values of (1.35 +/- 0.2) * 1E8, (1.60 +/- 0.3) * 1E7, (1.35 +/- 0.3) * 1E7, and (2.35 +/- 0.5) * 1E6 dm3 mol-1 s-1 indicate a nucleophilic character of the methyl radical.From Taft's relationship on the inductive substituent effect, ρ* + 8.9 is derived.The optical absorption spectra of the methyl radical adducts, R1R2CH3NO2.-, are characterized by λmax. 270 nm and extinction coefficients of (2.8-3.0) * 1E3 dm3 mol-1 cm-1.
- Veltwisch, Dieter,Asmus, Klaus-Dieter
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p. 1143 - 1146
(2007/10/02)
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- SYNTHETICALLY USEFUL OXIDATIONS AT SOLID PERMANGANATE SURFACES
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Solid NaMnO4.H2O is an efficient and selective oxidizing agent.
- Menger, Fredric M.,Lee, Chuan
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p. 1655 - 1656
(2007/10/02)
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- Far infra-red absorption of disubstituted propanes in rotator, solid and liquid phases
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Experimental observations of the far infra-red (f.i.-r.) absorption spectra of three polar di-substituted propanes (2,2-dichloro-, 2-chloro-2-nitro-, 2-methyl-2-nitro-propane) over the temperature range 133-303 K in the liquid, rotator and non-rotator solid phases are reported. The spectra in both the liquid and rotator phases are discussed in terms of two simple theoretical models of librational and relaxational motions: an acceptable fit to the experimental spectra is obtained on the basis of reasonable barriers and other parameters of the molecular motion. One of the models indicates that the molecular librational potential wells may become narrower with decreasing temperature and that there may be a distribution of potential well depths or shapes. The variation of potential barrier height with group substitution is also discussed.
- Haffmans,Larkin
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p. 1729 - 1741
(2007/10/12)
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