Gas-phase Nucleophilic Displacement Reactions

Riveros, José M.; José, Sonia Maria; Takashima, Keiko

doi:10.1016/s0065-3160(08)60100-8

Cited by 71 publications

(54 citation statements)

References 98 publications

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“…To isolate the role of solvation, however, it is necessary to look at thermoneutral reactions (11), such as isotopic exchange. Interpretation of an activation barrier for exothermic reactions requires a knowledge of the exothermicity and the intrinsic barrier of the reaction (12, 13), thus making gas-phase versus solution interpretations difficult, at best.Numerous gas-phase studies have shown that alkyl bulk does affect reactivity in the absence of solvent (10,11,(14)(15)(16)(17)(18). Thermoneutral reactions of alkyl halides have proven to be too slow, so only exothermic reactions have been studied.…”

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confidence: 99%

Steric Effects and Solvent Effects in Ionic Reactions

Regan

Craig

Brauman

2002

Science

113

110

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Rates of SN2 reactions of chloride ion with methyl- and tert-butyl-substituted chloroacetonitrile were measured by using Fourier transform-ion cyclotron resonance spectrometry to follow the isotopic exchange reaction. Barrier heights for these reactions indicate that steric effects in the gas phase are diminished relative to apparent steric effects in solution. We attribute the increased barrier in solution to a solvation effect. Monte Carlo simulations done using statistical perturbation theory confirm that steric hindrance to solvation contributes to SN2 barriers in solution.

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mentioning

confidence: 99%

Steric Effects and Solvent Effects in Ionic Reactions

Regan

Craig

Brauman

2002

Science

113

110

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“…Details of the experimental apparatus can be found elsewhere. [10][11][12] Briefly, the ICR system consists of a 2ϫ 2ϫ 2 in cubic cell, constructed from six stainless-steel plates mounted on Vespel rods. Ions were trapped with magnetic fields in the range 0·6-0·8 T. Neutral samples were admitted to the high-vacuum can by means of Varian leak valves.…”

Section: Methodsmentioning

confidence: 99%

“…Although the Riveros reaction, equation (1), is the major reaction pathway for methoxide, 11,15,16 Table 1 shows that in the reaction between benzyl anion and various formates, no S N 2 or Riveros reaction products were observed. For ethyl and especially tert-butyl formate, we observe secondary Riveros reaction products:…”

Section: Proton Transfer Vs Transacylationmentioning

confidence: 99%

“…transacylation, are of major importance in organic synthesis and in biological systems and have been studied extensively in condensed-and gas-phase studies. 5,[10][11][12][13][14][15] At least some of the comparisons between localized and delocalized ions can be made more effectively if the thermodynamics of the reactions are comparable. Previous studies 5 focused on the allyl ion, which is more basic than the methoxide ion.…”

Section: Introductionmentioning

confidence: 99%

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Gas-phase ionic reactions of benzyl and methoxide anions

Gatev

Zhong

Brauman

1997

J. Phys. Org. Chem.

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“…Nevertheless, a deeper view on solvent effects was only possible with experimental studies of gas phase ion-molecule reactions [2][3][4][5][6] and theoretical modeling of these processes. [7][8][9] It was evident from theoretical studies that solute-solvent interactions can be very strong and produce a profound effect on chemical reactivity.…”

Section: Introductionmentioning

confidence: 99%

How Accurate is the SMD Model for Predicting Free Energy Barriers for Nucleophilic Substitution Reactions in Polar Protic and Dipolar Aprotic Solvents?

Miguel¹,

Santos²,

Silva³

et al. 2016

Journal of the Brazilian Chemical Society

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In the past seven years, the SMD (Solvent Model Density) method has been widely used by computational chemists. Thus, assessment on the reliability of this model for modeling chemical process in solution is worthwhile. In this report, it was investigated six anion-molecule nucleophilic substitution reactions in methanol and dipolar aprotic solvents. Geometry optimizations have been done at SMD/X3LYP level and single point energy calculations at CCSD(T)/TZVPP + diff level. Our results have indicated that the SMD model is not adequate for dipolar aprotic solvents, with a root of mean squared (RMS) error of 5.6 kcal mol . The classical protic to dipolar aprotic solvent rate acceleration effect was not predicted by the SMD model for the tested systems.Keywords: continuum solvation model, ion solvation, solvent effect, aromatic nucleophilic substitution, M11 functional IntroductionIn the middle of the twentieth century, several experimental studies have led to foundation of empirical rules for qualitative prediction of solvent effects on chemical reactions, authoritatively reviewed by Parker 1 in a classical paper. Nevertheless, a deeper view on solvent effects was only possible with experimental studies of gas phase ion-molecule reactions [2][3][4][5][6] and theoretical modeling of these processes. [7][8][9] It was evident from theoretical studies that solute-solvent interactions can be very strong and produce a profound effect on chemical reactivity. [10][11][12][13][14][15][16][17] On the other hand, gas phase dynamic of chemical reactions can open new mechanistic possibilities. 18,19 Among the different solvents used to conduct ionic chemical reactions, polar protic and dipolar aprotic solvents are paramount due to their property of solubilize ionic species. 20 Methanol is a polar protic solvent and its ability to solvate ions is similar to water. 21,22 In addition, it has the advantage of solubilize many organic molecules not soluble in water. Some usual dipolar aprotic solvents are dimethyl sulfoxide (DMSO), dimethylformamide (DMF) and acetonitrile. Because anions are less solvated in these solvents, anion-molecule reactions are accelerated when transferred from protic to dipolar aprotic solvents. Our ability to describe theoretically this effect is an important goal and a challenge for continuum solvation models once requires these models be able to describe specific solutesolvent interactions. 23 Considering that the Born formula for solvation of a spherical ion of charge q and radius R into a solvent with dielectric constant ε is given by:(1) it could be noted that the use of the same "molecular cavity" for an ionic solute into a protic and dipolar aprotic solvent with high dielectric constant would lead to very similar solvation free energy of ions. A possibility to overcome this problem would be to use different molecular cavity for protic and dipolar aprotic solvents. This approach has reached some successful ten years ago using the polarizable continuum model (PCM) in the study of anion-molecule reaction...

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Gas-phase Nucleophilic Displacement Reactions

Cited by 71 publications

References 98 publications

Steric Effects and Solvent Effects in Ionic Reactions

Steric Effects and Solvent Effects in Ionic Reactions

Gas-phase ionic reactions of benzyl and methoxide anions

How Accurate is the SMD Model for Predicting Free Energy Barriers for Nucleophilic Substitution Reactions in Polar Protic and Dipolar Aprotic Solvents?

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