- Oxygen carriers based on electrochemically reduced trinitroarenes
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1,3,5-Trinitrobenzene, 2,4,6-trinitrotoluene and 1-methoxy-2,4,6- trinitrobenzene undergoes reversible dimerization, after electrochemical reduction of two units of corresponding anion radical. The π-dimer formed captures molecular oxygen (O2)
- Gallardo, Iluminada,Guirado, Gonzalo
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- Nucleophilic aromatic substitution for heteroatoms: An oxidative electrochemical approach
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The nucleophilic aromatic substitution for heteroatom through electrochemical oxidation of the intermediate σ-complexes (Meisenheimer complexes) in simple nitroaromatic compounds is reported for the first time (NASX process). The studies have been carried out with hydride, cyanide, fluoride, methoxy, and ethanethiolate anions and n-butylamine as a nucleophile, at the cyclic voltammetry (CV) and preparative electrolysis level. The cyclic voltammetry experiments allow for detection and characterization of the σ-complexes and they have led us to a proposal for the mechanism of the oxidation step. Furthermore, the power of the CV technique in the analysis of the reaction mixture throughout the whole chemical and electrochemical process is described.
- Gallardo, Iluminada,Guirado, Gonzalo,Marquet, Jordi
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p. 2548 - 2555
(2007/10/03)
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- Kinetics and mechanism of reactions between 2,4,6-trinitrofluorobenzene and alcohols
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The kinetics of formation of some ethers from alcohols and 2,4,6-trinitrofluorobenzene were studied under first order conditions ([ROH]o > [TNFB]o). In CCl4, k (in dm3 s-1 mol-1) values are increased on increasing the values of the initial concentrations of the alcohols. This anomalous kinetic behaviour parallels that of reactions between amines and activated aromatic fluoro derivatives. The presence of a substrate-alcohol interaction which precedes the substitution process explains the kinetic behaviour of the alcohols.
- Forlani, Luciano,Boga, Carla,Forconi, Marcello
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p. 1455 - 1458
(2007/10/03)
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- The activation of SNAr reactions by the superstrong electron-withdrawing substituent CF3S(O)=NSO2CF3
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The chlorine lability of the 2-nitrochlorobenzene derivative which contains the superstrong electron-withdrawing substituent CF3S(O)=NSO2CF3 in position 4 has been compared with the analogous 4-trifluoromethylsulphonyl derivative and picryl chloride in nucleophilic substitution.During interaction with hard nucleophilic agents, the effect of one superstrong substituent approximately corresponds to the influence of two nitro groups in positions 2 and 4.With soft reagents, picryl chloride is more active than the compound containing the CF3S(O)=NSO2CF3 group, polarizable only with difficulty.
- Boiko, V. N.,Kirii, N. V.,Yagupolskii, L. M.
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p. 119 - 124
(2007/10/03)
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- Phosphotriesters Approach to the Synthesis of Oligonucleotides: A Reappraisal
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The phosphotriester approach to the synthesis of oligodeoxyribo- and oligoribo-nucleotides in solution has been reinvestigated.The efficacy of mesitylene-2-sulfonyl chloride (MSCl) 15a, 2,4,6-triisopropylbenzenesulfonyl chloride (TrisCl) 15b, 4-bromobenzenesulfonyl chloride 15c, naphthalene-1-sulfonyl chloride 39, and 2- and 4-nitrobenzenesulfonyl chlorides 40a and 40b, respectively, as activating agents has been examined.The latter arenesulfonyl chlorides have been used in conjunction with the following nucleophilic catalysts: 1-methylimidazole, 3-nitro-1H-1,2,4-triazole 19, 5-(3-nitrophenyl)-1H-tetrazole 20a, 5-(3,5-dinitrophenyl)-1H-tetrazole 20b, 5-(1-methylimidazol-2-yl)-1H-tetrazole 21, 5--1H-tetrazole 22, 4-ethoxypyridine 1-oxide 14a, 4,6-dinitro-1-hydroxybenzotriazole 29a, 1-hydroxy-4-nitro-6-(trifluoromethyl)benzotriazole 29b, 1-hydroxy-5-phenyltetrazole 30a and 1-hydroxy-5-(3-nitrophenyl)tetrazole 30b.The rates of formation and yields of the fully protected dideoxyribonucleoside and diribonucleoside phosphates 37 and 47, respectively, were determined using various combinations of activating agents and nucleophilic catalysts.Although 2- and 4-nitrobenzenesulfonyl chlorides 40a and 40b, respectively, proved to be the most powerful activating agents, their use in the deoxy-series led to the formation of by-products and hence to unsatisfactory isolated yields of the dideoxyribonucleoside phosphate 37.
- Reese, Colin B.,Pei-Zhuo, Zhang
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p. 2291 - 2302
(2007/10/02)
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- Reaction of (E)-O-Arylbenzaldoximes with Sodium Methoxide in Methanol. Effect of Leaving Group upon Nitrile-Forming Transition State
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Reactions of (E)-O-arylbenzaldoximes 1-3 with MeONa-MeOH have been studied kinetically.The reactions proceed via competing E2 and SNAr reactions, in which the first step is rate-determining.Although the reactions were strongly influenced by the electronic effect of the β- and O-aryl substituents, they were insensitive to the steric effect of the O-aryl group, except that the SNAr reaction was retarded by the CF3 group of 2.For eliminations from 1-3 promoted by MeONa-MeOH, the kH/kD value increased and the Hammett ρ value decreased with better leaving groups.From these results, the effect of leaving group variation upon the nitrile-forming transition state is assessed.
- Cho, Bong Rae,Jung, Jinhee,Ahn, Eun Kyung
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p. 3425 - 3429
(2007/10/02)
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- Reactions of the super-electrophile, 2-(2',4'-dinitrophenyl)-4,6-dinitrobenzotriazole 1-oxide, with methoxide and tert-butoxide: basicity and steric hindrance as factors in ?-complex formation versus nucleophilic displacement
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The course of the reactions of methoxide and tert-butoxide with 2-(2',4'-dinitrophenyl)-4,6-dinitrobenzotriazole 1-oxide (4) clearly shows that the C-7 electrophilic site is significantly more reactive than the C-1' site of the substrate.The reaction pathways of these alkoxides, which differ in basicity (as a measure of nucleophilicity) and steric bulk, were followed by 400 MHz 1H nuclaear magnetic resonance spectroscopy.While both alkoxides lead to immediate formation of the respective C-7 anionic ?-adducts, a greater percentage of C-7 adduct formation occurs with methoxide as attacking nucleophile.Reactions with excess alkoxide results in attack at C-1' being observed, as well.This leads to formation of metastabile C-1' ?-adducts, whose rapid decomposition results in formation of 2,4-dinitrophenyl ethers and the dinitrobenzotriazole 1-oxyanion in an overall nucleophilic displacement reaction.Under these excess conditions, methoxide also causes a faster rate of displacement than does tert-butoxide as nucleophile.These results are discussed on the basis of the basicity of the nucleophiles, the relative electrophilicity of the positions in the substrate (C-7 versus C-1'), the steric hindrance involved in attack and in the resultant C-7 and C-1' complexes, and in terms of an activation energy/reaction coordinate profile comparing the pathways for attack at the two electrophilic sites. Key words: anionic ?-complexes, super-electrophiles, aromatic nucleophilic substitution (SNAr)
- Dust, Julian M.,Buncel, Erwin
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p. 978 - 986
(2007/10/02)
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- The Stabilities of Meisenheimer Complexes. Part 39. Steric Effects on Rate and Equilibrium Constants for ?-Adducts Formation from Alkyl 2,4,6-Trinitrophenyl Ethers and Ethoxide Ions in Ethanol
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Rate and equilibrium data are reported for reactions of ethoxide ions in ethanol with four alkyl 2,4,6-trinitrophenyl ethers to give isomeric 1,3 and 1,1 ?-adducts.The results indicate the importance of streric factors in this series.Increasing the size of the alkyl substituent causes decreases in values of k3, the rate coefficient, and K3, the equilibrium constant, for reaction at the unsubstituted 3-position, and also causes decreases in values of k1 for reaction at the substituted position.
- Cooney, Aidan,Crampton, Michael R.
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p. 1793 - 1796
(2007/10/02)
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- COMPLEXES OF PYRENE WITH 2,4,6-TRINITROANISOLE. STUDIES OF ASSOCIATION IN SOLUTION AND THE CRYSTAL STRUCTURE OF THE 1:1 COMPLEX
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Cyclohexane solutions of 2,4,6-trinitroanisole (A) containing excess pyrene (D) can be described in terms of a double equilibrium involving complexes DA and D2A.Formation constants for these complexes from A and from DA respectively from three independent experiments are in good agreement, the average values being K1=9.7 kg mol-1 and K2=1.8 kg mol-1 at 33.5 degC.The crystalline complex was obtained by gel diffusion.The mw (C23H15N3O7) corresponds to 1:1 stoichiometry C16H10, C7H5N3O7, X-ray structure data: P21/c, a=10.633(7), b=16.336(8), c=11.683(7) Angstroem, β=94.62(12) deg , V=2023 Angstroem, F000=924, μ(CuKα)=8.3 cm-1, Z=4.R=O.O91 for 1572 reflexions.The crystal contains extended stacks ADADA, parallel to (101).The pyrene molecules are disordered by rotation over two sites.The majority site has an accupancy factor of 0.544(2).The angle between te normals to the mean planes of A and D is 7.0(4) deg , allowing the nitro groups of A to twist out of the plane of the benzene ring by 41.0(1.0), 2.7(5) and 20.7(8) deg.
- Barnes, J. C.,Chudek, J. A.,Foster, R.,Jarrett, F.,Mackie, F.,et al.
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p. 1595 - 1602
(2007/10/02)
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- KINETICS OF REACTION OF 1-CHLORO-2,4,6-TRINITROBENZENE WITH ENOLATE IONS OF 2,4-PENTANEDIONE AND METHYL 3-OXOBUTANOATE
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Reaction of 1-chloro-2,4,6-trinitrobenzene (I) with anions of 2,4-pentanedione (II) and methyl 3-oxobutanoate (III) produces 3-(2,4,6-trinitrophenyl)-2,4-pentanedione (IV) and methyl 2-(2,4,6-trinitrophenyl)-3-oxobutanoate (V), respectively, besides 2,4,6-trinitrophenol (VI).Amount of 2,4,6-trinitrophenol decreases with increasing amount of dimethyl sulphoxide and 2,4-pentanedione in methanol.A mechanism of formation of 2,4,6-trinitrophenol is suggested.Rate constant of formation of 3-(2,4,6-trinitrophenyl)-2,4-pentanedione in methanol-dimethyl sulphoxide mixtures increases with increasing content of dimethyl sulphoxide and decreases with increasing LiCl concentration.In methanol, 1-chloro-2,4,6-trinitrobenzene reacts with anion of 2,4-pentanedione about 20x slower than with anion of methyl 3-oxobutanoate.
- Machacek, Vladimir,Andrle, Jaroslav,Sterba, Vojeslav
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p. 1608 - 1617
(2007/10/02)
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- Betylates. 4. The synthesis and preparative nucleophilic substitution reactions of alkyl S-betylates
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Alkyl S-betylates (S,S-dialkyl-S-3propylsulfonium salts), the first examples of S-betylates (sulfonioalkanesulfonic esters), have been synthesized by two routes, and their suitability as intermediates in the transformation of alcohols by nucleophilic substitution reactions examined.They have been found to react readily in stoichiometric phase transfer processes, including substrate-reagent ion-pair reactions, like their previously studied nitrogen analogues, with the following particular features: (a) they may be used with basic nucleophiles (unlike betylates), (b) they are more simply made from commercially available starting materials than betylates, and (c) they can be made by a route that avoids a final alkylation step.
- King, James Frederick,Skonieczny, Stanislaw,Poole, Gary Allan
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p. 235 - 243
(2007/10/02)
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- KETONITRONE ESTERS AND THEIR KETALS IN THE ALKYLATION OF SALTS OF NITROPHENOLS AND THE CORRESPONDING MEISENHEIMER COMPLEXES
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A study has been carried out of the formation of ethers in the alkylation of the silver salts of nitrophenols by alkyl halides, and of the corresponding cyclic ketals of the ketonitrone ethers in the alkylation of alkali metal salts of Meisenheimer comple
- Drozd, V. N.,Grandberg, N. V. (Tokmakova),Udachin, Yu. M.
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p. 1082 - 1089
(2007/10/02)
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- Stereoelectronic and Conformational Effects in Meisenheimer Complexes. Intrinsic Reactivities of Spiro vs. 1,1-Dimethoxy and 1-Methoxy-1-phenoxy Complexes
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Rate and equilibrium constants of formation of spiro Meisenheimer complexes derived from 1-(2-hydroxyethoxy)-2,6-dinitro-4-X-benzenes in aqueous solution are compared with those for 1,1-dimethoxy Meisenheimer complexes derived from 2,4-dinitro-4-X-anisoles.Hammett ρ values for the equilibrium constants are 8.2 for the dimethoxy and 5.9 for the spiro complexes, while the normalized ρ values for the rate constants of complex formation (cleavage) are 0.44 (-0.56) for the dimethoxy and 0.58 (-0.42) for the spiro complexes.The large difference in the equilibrium ρ values is attributed to a conformation of a dimethoxy complexes in which there is repulsion between the lone pairs on the ketal and the o-nitro group oxygens.A procedure for making the reactions in the two families thermodynamically comparable by correcting the rate and equilibrium constants for the pKa difference in the nucleophile and for intramolecularity of spiro complex formation was applied.The corrected parameters show that the spiro complexes form and decompose much faster than the dimethoxy complexes.This enhanced reactivity, ΔΔG, is attributed to a stereoelectronic effect or p-? overlap between a lone pair orbital of the nonreacting oxygen and the benzene ring, which is only feasible in the transition state of the spiro complex reaction (14) but not in the thransition state of the dimethoxy complex reaction (15).This interpretation is strongly supported by the fact that ΔΔG increases with increasing electron-withdrawing strength of X substituent.The enhanced rate of formation and decomposition of the spiro complex from catehol 2,4,6-trinitrophenyl ether compared to that of the corresponding 1-methoxy-1-phenoxy complex can be explained in a similar way.
- Bernasconi, Claude F.,Howard, Keith A.
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p. 7248 - 7257
(2007/10/02)
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- ACTION OF NITRIC ACID ON 2,4,6-TRINITROPHENYL ARENE AND ALKANECARBOTHIOATES
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For the case of the reaction of S,S'-bis(2,4,6-trinitrophenyl)dithiooxalate with concentrated nitric acid it was found that the sulfur-containing groups in the esters of thiocarboxylic acids are substituted by hydroxy and nitroso groups.The reaction, which is accompanied by copious release of nitrogen oxides and increase in temperature, leads to 2,4,6-trinitrophenol or 2,4,6-trinitronitrosobenzene.The structure of the latter was confirmed by IR and UV spectroscopy and by oxidation to 1,2,3,5-tetranitrobenzene. 2,4,6-Trinitrophenyl benzenecarbothioates give the nitroderivative only when the acids contain not more than one nitro group in the phenyl radical.The nitroso group in 2,4,6-trinitronitrosobenzene, like the halogen in picryl halides, is readily substituted by the action of nucleophilic reagents.
- Nurgatin, V. V.,Sharnin, G. P.,Savel'eva, L. A.,Nurgatina, R. B.
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p. 2167 - 2169
(2007/10/02)
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- Pressure Effect on Rate and Equilibrium Constants of Reversible Anionic ?-Complex Formation between Polynitroaromatics and Lyate Ions of Water and Methanol
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The kinetics of the following reversible anionic ?-complex formation reactions was studied by the high-pressure stopped-flow method up to 1500 bar at 25 deg C: 2,4,6-trinitroanisole + MeO- ->- 2 in methanol, 1-methoxy-2,4-dinitronaphthalene +
- Sasaki, Muneo,Takisawa, Noboru,Amita, Fujitsugu,Osugi, Jiro
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p. 7268 - 7272
(2007/10/02)
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- Kinetic Studies on the Decomposition of Most Typical Meisenheimer Complex of Sodium 1,1-Dimethoxy-2,4,6-trinitrocyclohexadienide in Methanol
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The whole decomposition of the Meisenheimer complex formed from 2,4,6-trinitroanisole (TNA) and sodium methoxide proceeds in three steps and obeys the first-order kinetics in each step.The rate of the whole decrease of concentration of the complex is given by -d(+->)/dt=(k1+>+k2)*+(k3+>+k4)*->-k5->*, where k denotes a rate constant.This leads to the modification of the conventional unimolecular mehanism shown by TNA*CH3O- -> TNA +CH3O-.
- Abe, Takehiro
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p. 1399 - 1405
(2007/10/02)
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