SN2 Reactions (sn2 + reaction)

Distribution by Scientific Domains
Distribution within Chemistry


Selected Abstracts


ChemInform Abstract: C,F Bond Cleavage by Intramolecular SN2 Reaction of Alkyl Fluorides with O- and N-Nucleophiles.

CHEMINFORM, Issue 33 2009
Laijun Zhang
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


ChemInform Abstract: Stereoselective Synthesis of (Z)-Enethiols and Their Derivatives: Vinylic SN2 Reaction of (E)-Alkenyl(phenyl)-,3 -iodanes with Thioamides.

CHEMINFORM, Issue 51 2001
Masahito Ochiai'
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


Mechanism for the gas-phase reaction between OH and 3-methylfuran: A theoretical study

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 7 2008
Weichao Zhang
Abstract The mechanism for the OH + 3-methylfuran reaction has been studied via ab initio calculations to investigate various reaction pathways on the doublet potential energy surface. Optimizations of the reactants, products, intermediates, and transition structures are conducted using the MP2 level of theory with the 6-311G(d,p) basis set. The single-point electronic energy of each optimized geometry is refined with G3MP2 and G3MP2B3 calculations. The theoretical study suggests that the OH + 3-methylfuran reaction is dominated by the formation of HC(O)CHC(CH3)CHOH (P7) and CH(OH)CHC(CH3)C(O)H (P9), formed from two low-lying adducts, IM1 and IM2. The direct hydrogen abstraction pathways and the SN2 reaction may play a minor or negligible role in the overall reaction of OH with 3-methylfuran. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source]


Theoretical investigation of ion pair SN2 reactions of alkali isothiocyanates with alkyl halides.

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2005
Part 1.
Abstract The gas-phase ionic SN2 reactions NCS - + CH3F and ion pair SN2 reaction LiNCS + CH3F with inversion mechanism were investigated at the level of MP2(full)/6-311+G**//HF/6-311+G**. Both of them involve the reactants complex, inversion transition state, and products complex. There are two possible reaction pathways in the ionic SN2 reaction but four reaction pathways in the ion pair SN2 reaction. Our results indicate that the introduction of lithium significantly lower the reaction barrier and make the ion pair displacement reaction more facile. For both ionic and ion pair reaction, methyl thiocyanate is predicted to be the major product, but the latter is more selective. More-stable methyl isothiocyanate can be prepared by thermal rearrangement of methyl thiocyanate. The theoretical predictions are consistent with the known experimental results. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source]


SN2 reaction of a sulfonate ester in the presence of alkyltriphenylphosphonium bromides and mixed cationic-cationic systems

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 5 2006
Michael M. Mohareb
Abstract The effects of alkyltriphenylphosphonium bromides (CnTPB, n,=,10, 12, 14, 16) on the rates of SN2 reactions of methyl 4-nitrobenzenesulfonate and bromide ion have been studied. Observed first-order rate constants are significantly higher than those found for other cationic surfactants for the same reaction. The results have been analyzed by the pseudophase model of micellar kinetics and show true micellar catalysis in the sense that second-order micellar rate constants are higher than the second-order rate constants in water. An attempt has also been made to investigate mixed cationic,cationic surfactant systems with respect to observed rates and pseudophase regression parameters. In addition, modeling of some cationic head groups has illustrated possible differences in head group charges and counterion interactions that may prove kinetically relevant. Copyright © 2006 John Wiley & Sons, Ltd. [source]


The size of the alpha-effects in methyl transfers correlate with Koopmans' theorem ionization potentials

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 6 2005
K. R. Fountain
Abstract The size of the alpha-effects in methyl transfers to the alpha-nucleophile's peroxide anion and two N -methylbenzohydroxamate anions correlate strongly with the Koopmans' theorem ionization potentials of the leaving groups. This correlation supports the Shaik and Pross valence bond configuration mixing theory for the SN2 reaction. The Koopmans' theorem ionization potentials of the alpha-nucleophiles relate to the slopes of the regression plots inversely, indicating that the size of the alpha-effect depends on a balance between the ability of the alpha-nucleophile and the leaving group to donate single electron character to the methyl group. Copyright © 2005 John Wiley & Sons, Ltd. [source]


Looking for a contribution of the non-equilibrium solvent polarization to the activation barrier of the SN2 reaction

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 6 2002
Jan S. Jaworski
Abstract The solvent effect on the activation free energy of the Finkelstein reaction between methyl iodide and Cl, ions was analysed in terms of the recent Marcus theory unifying the SN2 and the electron transfer reactions. The homolytic bond dissociation energy and the related resonance energy of interaction of the states seem to be almost solvent independent. The sum of the work term wr and the solvent reorganization energy ,0/4 depends strongly on the solvent acidity parameter, e.g. ETN, describing the solvation/desolvation of anions. However, after removing the contribution of the specific solvation the linear increase of the remaining part of ,0/4 with the Pekar factor, describing the non-equilibrium solvent polarization, was observed for six aprotic solvents. Copyright © 2002 John Wiley & Sons, Ltd. [source]


Stereoselective Synthesis of Bicyclic Nitrocyclopropanes by a Radical,Anion Domino Reaction

CHEMISTRY - A EUROPEAN JOURNAL, Issue 40 2009
Akio Kamimura Prof.
A novel one-step radical-ionic cyclopropanation was carried out to prepare aza- or oxabicyclo[3.1.0]hexane from ,-nitroamides or ,-nitroethers in a stereoselective manner (see scheme). The present procedure involves a higher-order domino process that includes one-electron oxidation, radical cyclization,intramolecular SN2 reaction. [source]


The Effect of Ring Size on Reactivity: The Diagnostic Value of ,Rate Profiles'

HELVETICA CHIMICA ACTA, Issue 6 2005
Eric Masson
The rates of cycloalkyl phenyl sulfide formation of a series of homologous bromocycloalkanes upon treatment with sodium benzenethiolate have been determined to ascertain the effect of ring size on reactivity. The ,rate profile', i.e., reaction rate vs. ring size, for these nucleophilic substitutions (SN2) was determined. A linear free-energy relationship could be derived from computed hydride affinities of cycloalkanes and rates of typical SN1 reactions, whereas rates of SN2 reactions exhibited a strong discrepancy from the seven- up to the twelve-membered rings. This discrepancy was rationalized by a careful examination of the geometry of the intermediates and transition states involved in these reactions. [source]


Kinetic studies of hydrazine and 2-hydroxyethylhydrazine alkylation by 2-chloroethanol: Influence of a strong base in the medium

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 6 2009
V. Goutelle
To optimize yields, the study of reaction kinetics related to the synthesis of 2-hydroxyethylhydrazine (HEH) obtained from the alkylation of N2H4 by 2-chloroethanol (CletOH) was carried out with and without sodium hydroxide. In both cases, the main reaction of HEH formation was followed by a consecutive, parallel reaction of HEH alkylation (or dialkylation of N2H4), leading to the formation of two isomers: 1,1-di(hydroxyethyl)hydrazine and 1,2-di(hydroxyethyl)hydrazine. In this study, hydrazine and hydroxyalkylhydrazine alkylations followed SN2 reactions triggered directly by CletOH or indirectly in the presence of a strong base by ethylene oxide, an intermediate compound. The kinetics was studied in diluted mediums by quantifying HEH and CletOH by gas chromatography and gas chromatography coupled with mass spectrometry (GC-MS). The activation parameters of each reaction and the influence of a strong base present in the medium on the reaction mechanisms were established. A global mathematical treatment was applied for each alternative. It allowed modeling the reactions as a function of reagent concentrations and temperature. In the case of direct alkylation by CletOH, simulation was established for semi-batch and batch syntheses and was confirmed in experiments for concentrated mediums (1.0 M , [CletOH]0 , 3.2 M and 15.7 M , [N2H4]0 , 18.8 M). Simulation therefore permits the prediction of the instantaneous concentration of reagents and products, in particular ethylene oxide concentration in the case of indirect alkylation, which must be as weak as possible. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 382,393, 2009 [source]


Nonequilibrium solvent polarization in kinetics of SN2 reactions

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 2 2003
J. S. JaworskiArticle first published online: 21 NOV 200
The solvent effect on the experimental activation barriers for the reactions of methyl iodide with chloride and thiocyanate ions was analyzed according to the Marcus and Shaik theories, considering SN2 mechanism in terms of a single electron shift. The linear increase in the solvent reorganization energy of the Marcus theory (after removing contributions from the specific solvation) with the solvent Pekar factor, describing the effect of the nonequilibrium solvent polarization, was observed for six aprotic solvents. The direct support of the title effect based on the Shaik theory was less evident; however, in general, the calculated activation barriers in 10 solvents change parallel with the experimental ones. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 61,66, 2003 [source]


Theoretical study of the gas-phase SN2 reactions of X, with CH3OY (X, Y = Cl, Br, I)

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 5 2007
Jing-Gang Gai
Abstract The gas-phase nucleophilic substitution reactions at saturated oxygen X, + CH3OY (X, Y = Cl, Br, I) have been investigated at the level of CCSD(T)/6-311+G(2df,p)//B3LYP/6-311+G(2df,p). The calculated results indicate that X, preferably attacks oxygen atom of CH3OY via a SN2 pathway. The central barriers and overall barriers are respectively in good agreement with both the predictions of Marcus equation and its modification, respectively. Central barrier heights (,H and ,H) correlate well with the charges (Q) of the leaving groups (Y), Wiberg bond orders (BO) and the elongation of the bonds (OY and OX) in the transition structures. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source]


Theoretical investigation of ion pair SN2 reactions of alkali isothiocyanates with alkyl halides.

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2005
Part 1.
Abstract The gas-phase ionic SN2 reactions NCS - + CH3F and ion pair SN2 reaction LiNCS + CH3F with inversion mechanism were investigated at the level of MP2(full)/6-311+G**//HF/6-311+G**. Both of them involve the reactants complex, inversion transition state, and products complex. There are two possible reaction pathways in the ionic SN2 reaction but four reaction pathways in the ion pair SN2 reaction. Our results indicate that the introduction of lithium significantly lower the reaction barrier and make the ion pair displacement reaction more facile. For both ionic and ion pair reaction, methyl thiocyanate is predicted to be the major product, but the latter is more selective. More-stable methyl isothiocyanate can be prepared by thermal rearrangement of methyl thiocyanate. The theoretical predictions are consistent with the known experimental results. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source]


Modified Gaussian-2 level investigation of the identity ion-pair SN2 reactions of lithium halide and methyl halide with inversion and retention mechanisms

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 4 2004
Yi Ren
Abstract Identity ion-pair SN2 reactions LiX + CH3X , XCH3 + LiX (X = F, Cl, Br, and I) have been investigated in the gas phase and in solution at the level of the modified Gaussian-2 theory. Two possible reaction mechanisms, inversion and retention, are discussed. The reaction barriers relative to the complexes for the inversion mechanism [,H(inv)] are found to be much higher than the corresponding values for the gas phase anionic SN2 reactions, decreasing in the following order: F (263.6 kJ mol,1) > Cl (203.3 kJ mol,1) > Br (174.7 kJ mol,1) > I (150.7 kJ mol,1). The barrier gaps between the two mechanisms [,H (ret) , ,H (inv)] increase in the order F (,62.7 kJ mol,1) < Cl (4.4 kJ mol,1) < Br (24.9 kJ mol,1) < I (45.1 kJ mol,1). Thus, the retention mechanism is energetically favorable for fluorine and the inversion mechanism is favored for other halogens, in contrast to the anionic SN2 reactions at carbon where the inversion reaction channel is much more favorable for all of the halogens. The stabilization energies for the dipole,dipole complexes CH3X · · · LiX (,Hcomp) are found to be similar for the entire set of systems with X = F, Cl, Br, and I, ranging from 53.4 kJ mol,1 for I up to 58.9 kJ mol,1 for F. The polarizable continuum model (PCM) has been used to evaluate the direct solvent effects on the energetics of the anionic and ion-pair SN2 reactions. The energetic profiles are found to be still double-well shaped for most of the ion-pair SN2 reactions in the solution, but the potential profile for reaction LiI + CH3I is predicted to be unimodal in the protic solvent. Good correlations between central barriers [,H (inv)] with the geometric looseness of the inversion transition state %C,X,, the dissociation energies of the C,X bond (DC,X) and Li,X bond (DLi,X) are observed, respectively. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 461,467, 2004 [source]


SN2 reaction of a sulfonate ester in the presence of alkyltriphenylphosphonium bromides and mixed cationic-cationic systems

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 5 2006
Michael M. Mohareb
Abstract The effects of alkyltriphenylphosphonium bromides (CnTPB, n,=,10, 12, 14, 16) on the rates of SN2 reactions of methyl 4-nitrobenzenesulfonate and bromide ion have been studied. Observed first-order rate constants are significantly higher than those found for other cationic surfactants for the same reaction. The results have been analyzed by the pseudophase model of micellar kinetics and show true micellar catalysis in the sense that second-order micellar rate constants are higher than the second-order rate constants in water. An attempt has also been made to investigate mixed cationic,cationic surfactant systems with respect to observed rates and pseudophase regression parameters. In addition, modeling of some cationic head groups has illustrated possible differences in head group charges and counterion interactions that may prove kinetically relevant. Copyright © 2006 John Wiley & Sons, Ltd. [source]


The nitro anomaly and Brønsted ,nuc values in SN2 reactions on chlorine,

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 8 2002
Linoam Eliad
Abstract The kinetics of chlorine transfer reactions between N -chlorosuccinimide (NCS) and four carbon nucleophiles (the conjugated bases of phenyldinitromethane, Meldrum's acid, phenylmalononitrile and phenylnitro-methane) in water were determined. A plot of log k for the SN2 reactions vs the pKa of the first three conjugated acids of the nucleophiles gave a straight line with a slope (,nuc) of 1.8. The data point for the mononitro derivative, phenylnitromethane, deviates negatively from the line by 6.7 log units. This deviation is typical of proton transfer reactions and was recently shown to occur also in SN2 reactions on bromine. Copyright © 2002 John Wiley & Sons, Ltd. [source]