- GAS PHASE SULFUR ANIONS: SYNTHESIS AND REACTIONS OF H2NS(1-) AND RELATED IONS
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Many gas-phase anions react with carbonyl sulfide by sulfur atom transfer to form RS(1-) ions.The properties of H2NS(1-), formed in this way from H2N(1-) and OCS, are described.
- DePuy, Charles H.,Bierbaum, Veronica M.
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- Synthesis and biological evaluation of new antioxidant and antiproliferative chalcogenobiotin derivatives for bladder carcinoma treatment
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Approximately 90% of bladder carcinomas are of the urothelial carcinoma type, which are characterized by high rates of recurrence and predisposition to progress to invasive tumors, representing one of the most costly neoplasms for health systems. Intraves
- Collares, Tiago,Dornelles, Luciano,Leitemberger, Andrielli,Nogara, Pablo A.,Piccoli, Bruna C.,Rodrigues, Oscar E. D.,Schachtschneider, Kyle M.,Seixas, Fabiana K.,Sonego, Mariana S.,da Silva, Fernanda D.,dos Santos, Alana C. F.,Garcia, Fábio D.,Oliveira, Cláudia S.,Rocha, Jo?o B. T.
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- Mesolysis Mechanisms of Aromatic Thioether Radical Anions Studied by Pulse Radiolysis and DFT Calculations
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The mesolysis mechanisms for eight aromatic thioether radical anions (ArCH2SAr′?-) generated during radiolysis in 2-methyltetrahydrofuran were studied by spectroscopic measurements and DFT calculation. Seven of ArCH2SAr′s
- Yamaji, Minoru,Tojo, Sachiko,Fujitsuka, Mamoru,Sugimoto, Akira,Majima, Tetsuro
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p. 7890 - 7895
(2015/09/01)
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- Reactions of O-aryl S-aryl dithiocarbonates with pyridines in aqueous ethanol: Kinetics and mechanism
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The reactions of O-(4-methylphenyl) S-(4-nitrophenyl) dithiocarbonate (1), O-(4-chlorophenyl) S-(4-nitrophenyl) dithiocarbonate (2), and O-(4-chlorophenyl) S-phenyl) dithiocarbonate (3) with a series of pyridines were subjected to a kinetic investigation
- Castro, Enrique A.,Gazitua, Marcela,Santos, Jose G.
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scheme or table
p. 1003 - 1008
(2010/07/04)
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- Generation of alkoxycarbenium ion pools from thioacetals and applications to glycosylation chemistry
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(Chemical Equation Presented) Alkoxycarbenium ions have been generated and accumulated as "cation pools" by the low-temperature electrochemical oxidation of α-phenylthioethers. Although an unsuccessful attempt to accumulate glycosyl cations was made, a one-pot method for electrochemical glycosylation, which involves anodic oxidation of thioglycosides to generate glycosyl cation equivalents followed by their reactions with glycosyl acceptors, has been developed.
- Suzuki, Shinkiti,Matsumoto, Kouichi,Kawamura, Kohsuke,Suga, Seiji,Yoshida, Jun-Ichi
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p. 3755 - 3758
(2007/10/03)
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- Enhanced reactivity in the ammonolysis of phenyl thiolacetates in aqueous medium
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The ammonolysis of several substituted phenyl thiolacetates is kinetically studied in aqueous medium, 18°C, ionic strength 0.1 M (KCl). By following the leaving groups spectrophotometrically (λmax = 260-410 nm), under excess free ammonia, pseud
- Rajarathnam,Babu,Nadar, P. Ananthakrishna
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- Reduction potentials and kinetics of electron transfer reactions of phenylthiyl radicals: Comparisons with phenoxyl radicals
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The reduction potentials relative to the standard hydrogen electrode (SHE) for a number of para-substituted phenylthiyl radicals (Eo(p-XC6H4S./p-XC6H 4S-)) have been derived from pulse radiolytic studies of electron transfer equilibria which compare their values to those of radicals of known reduction potentials. A ladder combining the reduction potentials for both phenylthiyl and phenoxyl radicals has been established. These reduction potentials have been shown to be self-consistent and are intermediate between those of p-benzosemiquinone radical anion at 0.02 V and phenoxyl radical at 0.79 V. The reduction potential decreases as the electron donating power of the para substituent rises. The substituent effect is, however, much weaker for the phenylthiyl radicals than for their oxygen analogs. These observations demonstrate that the electronic interaction between the sulfur atoms and the aromatic ring system is much less than that which occurs with oxygen atoms. Examination of the rates of electron transfer in terms of the Marcus theory indicates that the reorganization energies of both p-XC6H4O. and p-XC6H4S. radicals are similarly affected by H, CH3, and CH3O substitution. However, the reorganization energies increase substantially for H2N and O- para substituents with the effect being much less for the p-XC6H4S. radicals than for the p-XC6H4O. radicals. These observations are in accord with structural information from spectroscopic and theoretical studies of the radicals which show that in the latter system the substituent groups interact strongly with the aromatic π system.
- Armstrong,Sun, Qun,Schuler
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p. 9892 - 9899
(2007/10/03)
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- Formation and scission of the sulfur-sulfur bond: a new approach to reactions between sulfur/polysulfide ions and thiolate ions/disulfides in N,N-dimethylacetamide
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The reactivity of sulfur towaards a series of thiolate ions RS- has been studied by spectroelectrochemistry in N,N-dimethylacetamide.Apparently, sulfur reacts in two parallel ways: (i) oxidation of RS- leading to RS2R and S3 anion radical ions; (ii) preponderant S-nucleophilic process yielding stable RSx- ions (x = 2-5).RSx- species, whose spectrophotometric characteristics have been determined, are successively obtained in the course of sulfur addition with R = alkyl, whereas equilibria between arylpolysulfide ions were observed.At the junction of these two parallel pathways, the slow keyequilibrium 2RS4- RS2R + 2S3 radical anion has been investigated by addition of RS2RR = 1-8 to S3 radical anion solutions.In fact, our study is consistent with a first, a monoelectronic transfer between RS- (or RS2-) ions and the very reactive S2 molecules in equilibrium with S8.The fact and competing couplings of the radicals RS (or RS2 radical), S2 radical anion (or S3 radical anion) agree with the simultaneous formation of RS2R, RSx- and polysulfide ions.More generally, the S2/S2 radical anion redox system is believed to be involved in thiophilic reactions of a number of anions such as RS- towards sulfur rather than the initial opening of the cyclic S8 form.
- Bosser, Gerard,Anouti, Meriem,Paris, Jacky
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p. 1993 - 2000
(2007/10/03)
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- Lifetimes of iminium ions in aqueous solution
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Iminium cations have been generated in aqueous solution from the solvolysis of anilinothioethers ArN-(CH3)CH2SR at 25 °C. Common ion inhibition of the solvolysis of anilinothioethers was observed when the thiolate anion leaving group
- Eldin, Sherif,Jencks, William P.
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p. 4851 - 4857
(2007/10/02)
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- Formation of Stable Aryldisulphide Ions in Dimethylacetamide from the Reaction of Sulphur with Thiolate Ions
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The conditions for the formation of aryldisulphide ions, RS2- during the direct reaction of sulphur with thiolate ions RS- have been studied by the use of spectroelectrochemistry in dimethylacetamide.The series of derivatives examined was R = p-tolyl (1), phenyl (2), 8-quinolyl (3), 2- and 4-pyridyl (4), (5), N-oxido 4-pyridyl (6), 2- and 4-nitrophenyl (7), (8), and 2-(5-nitropyridyl) (9).Sulphur reaction leads to RS2- ions and preceded the oxidation to diaryldisulphide RS2R and polysulphide ions Sx-.With derivatives (1)-(3), both reactions are successive and practically stoicheiometric, while for derivatives containing electron-withdrawing groups (6)-(9), the equilibrium constants have been measured.Analysis of the reaction products by methylation of several solutions of thiolate ions in the presence of sulphur confirmed the possibility of obtaining aryldisulphide ions stabilized in aprotic dipolar media.
- Benaichouche, Meriem,Bosser, Gerard,Paris, Jacky,Auger, Jacques,Plichon, Vincent
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- Relative Nucleophilicities of Aryldisulphide and Thiolate Ions in Dimethylacetamide Estimated from their Reaction Rates with Alkyl Halides
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The relative rates of nucleophilic substitution (SN2) of alkyl halides by aromatic thiolates ArS- and aryldisulphide ions ArS2- have been studied in dimethylacetamide by UV-visible spectrophotometry for Ar = 4-nitrophenyl (1), 2-nitrophenyl (2), and 8-quinolyl (3).Rate constants are relative to the rate constants for benzenethiolate ions (4), studied as reference.With Ar = (1), the reaction rate for disulphide ions is ten times higher than that for monosulphide ions stabilized by the elevated delocalization of their charge.With Ar = (2) and (3), the reactivity of disulphide ions is higher than that of the corresponding thiolates.Our study is consistent with the uncomplicated introduction of a disulphide bond into various substrates from aryldisulphide ions stabilized in aprotic dipolar media.
- Benaichouche, Meriem,Bosser, Gerard,Paris, Jacky,Plichon, Vincent
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p. 1421 - 1424
(2007/10/02)
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- Gas-Phase Reactions of Fe(1-) and Co(1-) with Simple Thiols, Sulfides, and Disulfides by Fourier Transform Mass Spectrometry
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Fe(1-) and Co(1-) are found to react with simple thiols, sulfides, and disulfides.The primary reaction products formed from these metal anions, M(1-), and thiols include MS(1-), MSH(1-), and MSH2(1-) and suggest a mechanism involving initial insertion of the metal into the weak C-S bond.Similarly, C-S insertion is the main mode of attack in the reactions with the sulfides and disulfides, in analogy to what is observed for the reaction of metal cations.Collision-induced dissociation is used to support the proposed structures for the primary products, H-Fe(1-)-SH andFe(1-)-SH.Some of the thermochemical data derived from this study include D0(M(1-)-S)>103 kcal/mol and D0(M(1-)-SH)=83 +/- 9 kcal/mol.Finally, a brief survey of the reactivity of V(1-), Cr(1-), and Mo(1-) with selected organosulfur compounds is also reported.
- Sallans, L.,Lane, K. R.,Freiser, B. S.
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p. 865 - 873
(2007/10/02)
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- Aromatization of Tetrahydrocyclopropanaphthalenes: an Alternative Synthesis of 1H-Cyclopropanaphthalene
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1H-Cyclopropanaphthalene (1a) is accessible via reduction of the dichloro compound 1c with LiAlH4/AlCl3.Several derivatives of tetrahydrocyclopropanaphthalene were synthesized.However, contrary to their 1,1-dihalogeno analogues, they afforded no cyc
- Mueller, Paul,Bernardinelli, Gerald,Thi, Huong Can Godoy-Nguyen
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p. 1627 - 1638
(2007/10/02)
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- Monosubstitution versus Disubstitution in the SRN1 Reaction of Dihalobenzenes with Sulfanions. The Role of the Monosubstitution Product and of Its Anion Radical
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The competition between mono- and disubstitution of dihalobenzenes by a series of aromatic sulfanions, via the SRN1 reaction, is shown to involve two radical chains.The first one, recognized in earliest works, involves one branching point at the level of the monosubstituted product anion radical.Reoxidation of the latter via electron transfer to the parent dihalide affords the monosubstituted product.Conversely, the route to the disubstituted product is opened when cleavage of the carbon-halogen bond in the monosubstituted product anion radical occurs before the electron transfer takes place; the disubstitution product is then obtained in its reduced (anion radical) form.Reoxidation of the latter, to afford the neutral disubstituted product, may involve competitively the parent dihalide or the neutral monosubstituted product, depending on the electron affinity of the arylthio moiety.In the first case the electron transfer propagates the first chain; in the second a new chain leading to the disubstitution is activated.The role of the two imbricated chains, under photochemical conditions, and thus that of the monosubstitution product is discussed quantitatively on the basis of the pertinent rate constants determined by cyclic voltammetry.
- Amatore, C.,Beugelmans, R.,Bois-Choussy, M.,Combellas, C.,Thiebault, A.
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p. 5688 - 5695
(2007/10/02)
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- The Oxidation of Dithiocarbamate Anion by Substitution Inert Metal Complexes
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The kinetics of oxidation of dithiocarbamate anions to thiuram disulfides in aqueous acetone by 3- and 11 other substitution inert metal complexes have been investigated.Outer-sphere electron transfer, resulting in the formation of dithiocarbamate thio radicals, is the rate determining step.A Marcus cross reaction treatment allows an estimate for the redox potential for the dithiocarbamate radical/anion couple.For diethyldithiocarbamate, Edeg(edtc./edtc-) = 425+/-33 mV ν.s.c.e. and the outer-sphere electron self-exchange rate constant is logkex = 7.0+/-0.3.A comparison with thiophenolate oxidation is also given.
- Nichols, Peter J.,Grant, Michael W.
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p. 1085 - 1102
(2007/10/02)
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- The Gas-Phase Smiles Rearrangement: A Heavy Atom Labeling Study
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Heavy atom ((13)C and (18)O) labeling shows that the product ion PhO- from PhO(CH2)2O- and products PhO- and PhS- from PhS(CH2)2O- are formed through Smiles intermediates I (X=Y=O or X=O, Y=S).The ana
- Eichinger, Peter C.H.,Bowie, John H.,Hayes, Roger N.
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p. 4224 - 4227
(2007/10/02)
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- Homogeneous and Heterogeneous Electron Transfer to Benzyl Phenyl Sulfide
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The thermodynamic and kinetic parameters of the elctron transfer (ET) to benzyl phenyl sulfide in DMF have been determined by cyclic voltammetry.The heterogeneous ET has been studied at three different electrodes: Hg, Pt, and glassy carbon.The activation parameters, namely the standard rate constant and the transfer coefficient, corrected for the double-layer contribution, show no significant difference for the three materials.The rate constants for the homogeneous ET to benzyl phenyl sulfide from eight electrogenerated anion radicals have been determined and compared with the corresponding reaction free energies, according to the current theories of the ET process.The results indicate that the ET is an endergonic process driven by a fast bond breaking of the ET product.Both the homogeneous and the heterogeneous reactions are consistent with an outer-sphere adiabatic electron-exchange process, characterized by a relatively high activation free energy.To account for the latter, inner reorganization energies must be considered, together with solvent reorganization.This is an agreement with the easy breaking of the C-S bond in the primari ET product.
- Severin, Maria Gabriella,Arevalo, Maria Carmen,Farnia, Giuseppe,Vianello, Elio
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p. 466 - 472
(2007/10/02)
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- Gas-Phase Synthesis and Reactions of Nitrogen- and Sulfur-Containing Anions
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The flowing afterglow and selected ion-flow tube techniques have been used to study the reactions of H2N- with N2O, CO2, CS2, SO2, and OCS in the gas phase.Thermal energy rate coefficients and product branching ratios have been determined and are discussed in terms of detailed reaction mechanisms.With use of the SIFT-drift technique, the product distribution for the reaction of H2N- with N2O was measured as a function of the center of mass kinetic energy in the range of thermal energy to ca. 15 kcal mol1-.Qualitative studies were made of the reactions of HO-, CH3O-, and (CH3)2N- with N2O, CO2, CS2, SO2, and OCS, and the reactions of a variety of other ions with OCS were also examined.These reactions provide efficient synthetic routes for the gas-phase preparation of a variety of interesting negative ions containing nitrogen and sulfur.The basicities and heats of formation of three of these anions, H2NS-, NSO-, and NCS-, have been bracketed by proton-transfer reactions.The nucleophilicities of these three anions, as well as of H2N-, HO-, HO2-, F-, HS-, CN-, NCO-, N3-, Cl-, and Br- toward CH3I, have been measured.
- Bierbaum, Veronica M.,Grabowski, Joseph J.,DePuy, Charles H.
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p. 1389 - 1393
(2007/10/02)
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- The E1cB Mechanism for Thiocarbamate Ester Hydrolysis: Equilibrium and Kinetic Studies
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The alkaline hydrolyses of a series of S-aryl thiocarbamate esters have been measured and the mechanism confirmed to be dissociative.Equilibrium constant for the synthesis of thiocarbamates from thiol and isocyanic acid have been obtained for aqueous media using both kinetic and analytical techniques.Hammett and Broensted parameters for the equilibrium reaction indicate that there is less positive effective charge on the sulphur in the thiocarbamate compared with that on the oxygen in the oxygen analogue.Theoretical arguments are advanced to show that the dissociative reactions of simple carbamate anions involve a planar geometry of the paticipating atoms.
- Bourne, Nicholas,Williams, Andrew,Douglas, Kenneth T.,Penkava, Thomas R.
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p. 1827 - 1832
(2007/10/02)
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- On Relative Leaving Abilities: Use of Isobasic Plots to Determine the Relative Nucleofugalities of Thiolates and their Oxy-analogues
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The use of an isobasic plot shows that, when structures are analogous and pKa values identical, RO- departs from acetoacetate ester anions 5 * 103 times faster than RS- and 79 times faster from fluorene-9-carboxylic acid ester anions, a reversal of the apparent order of nucleofugality determined by measured rates of elimination of RS- and RO-.
- Douglas, Kenneth T.,Alborz, Manoochehr
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p. 551 - 553
(2007/10/02)
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- Determination of Rate Constants for Electron Transfer from Radical Anions of Aromatic Compounds to Diaryl Disulfides
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Rate constants for electron transfer from the radical anions of aromatic compounds to diaryl disulfides (ArSSAr) have been determined in tetrahydrofuran.By the change of the reduction potentials of the aromatic compounds from -1.04 to -1.91 V (vs.SCE), the rate constants varied from 0.015 to 2.3 * 108 M-1 s-1; conventional spectrophotometry has been employed to measure the slow reaction rates, and the xenon-flash photolysis technique has been applied to the fast reaction systems.The reaction including the free ion or the loose ion pair of the thioxanthone sulfone radical anion, (TO-SO2)-/., was faster than that including the tight ion pair.In the case of the (TO-SO2)-/., Na+-PhSSPh system, temperature variation yielded the free energy of activation (ΔG* = 18.7 kcal/mol) and activation enthropy (ΔS* = -29.1 eu) at 22.4 deg C; the reduction potential of PhSSPh was estimated to be -1.80 V vs.SCE from ΔG* value.Electron-withdrawing substituents of ArSSAr increase the rates and vice versa; the Hammett reaction constants (ρ) were estimated to be ca. +1.50 and 1.40 for electron transfer from perylene radical anion and (TO-SO2)-/.,Na+ to ArSSAr, respectively.The factors controlling the rates have been examined.
- Tagaya, Hideyuki,Aruga, Tamotsu,Ito, Osamu,Matsuda, Minoru
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p. 5484 - 5489
(2007/10/02)
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- Photostimulated Reactions of Alkanethiolate Ions with Haloarenes. Electron Transfer vs. Fragmentation of the Radical Anion Intermediate
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The photostimulated reactions of RS(1-) ions (R = methyl, n-butyl, tert-butyl, and benzyl) with haloarenes in liquid ammonia were studied.Two main products were formed: alkyl aryl sulfide and arenethiolate ions.The formation of these compounds is explained by the SRN1 mechanism of aromatic nucleophilic substitution.The radical anion intermediate formed in the coupling of an aryl radical with an alkanethiolate ion undergoes two competing reactions: transfer of the odd electron to the substrate leading to the substitution product or bond fragmentation leading to arenethiolate ion and an alkyl radical.It is concluded that the ratio of these products depends mainly on changes in the rate of fragmentation and not on changes in the electron-transfer reaction.
- Rossi, Roberto A.,Palacios, Sara M.
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p. 5300 - 5304
(2007/10/02)
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- Effect of Solvation on the Nucleophilic Reaction of Stable Carbanions with Diaryl Disulfides
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Stable carbanions react with diaryl disulfides in aqueous solution by direct displacement (SN2) reaction to yield an arylthiol anion and the corresponding sulfide as products.The reaction of 1,3-dicarbonyl carbanions with 5,5'-dithiobis(2-nitrobenzoic acid) is characterized by Broensted βC value of 0.5.Nitroalkane carbanions react 102-104 slower than 1,3-dicarbonyl carbanions of the same pK and are correlated by a Broensted βC of 0.95.The second-order rate constants for the reaction of nitroalkane carbanions increase by factors of 104-106 as the solvent is changed from water to dimethyl sulfoxide.Smaller increases are observed in the rate constants for reaction of 2,4-pentadienone carbanion (102) and malonitrile carbanion (100.6) with the same sulfide.A linear correlation is found between log (kMe2SO4/kHOH) and the increase in pK for the carbon acid ionization on changing the solvent from water to dimethyl sulfoxide.The effect is attributed to large differences in ground-state carbanion solvation which are reduced or absent in the transition state.Parallels are drawn between the nucleophilic reaction of stable carbanions with diaryl disulfides and proton-transfer reactions of the same carbanions.
- Gilbert, H. F.
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p. 7059 - 7065
(2007/10/02)
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