A Theoretical Analysis of the Free-Energy Profile of the Different Pathways in the Alkaline Hydrolysis of Methyl Formate In Aqueous Solution

Pliego, Josefredo R.; Riveros, José M.

doi:10.1002/1521-3765(20020415)8:8<1945::aid-chem1945>3.0.co;2-t

Cited by 67 publications

(71 citation statements)

References 19 publications

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“…These values are reasonable estimates for the reaction in water. Nevertheless, because of the high specific interaction in aqueous solutions, a hybrid discrete/continuum approach would be needed for more accurate predictions [62]. We should in fact expect a higher barrier and more S N 2 product with a more extensive approach.…”

Section: The F − /Ch 3 Ch 2 Br Reactionmentioning

confidence: 99%

New insights on reaction pathway selectivity promoted by crown ether phase-transfer catalysis: Model ab initio calculations of nucleophilic fluorination

Pliego

Riveros

2012

Journal of Molecular Catalysis A: Chemical

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Section: The F − /Ch 3 Ch 2 Br Reactionmentioning

confidence: 99%

New insights on reaction pathway selectivity promoted by crown ether phase-transfer catalysis: Model ab initio calculations of nucleophilic fluorination

Pliego

Riveros

2012

Journal of Molecular Catalysis A: Chemical

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“…23,52,[63][64][65] Our group has successfully applied this model to some interesting ion-molecule reactions. 11,[66][67][68] The use of full explicit solvent molecules coupled with free energy perturbation was pioneered by Jorgensen, 69 and the rate acceleration effect was predicted for a classical S N 2 reaction. Acevedo and Jorgensen 70 have also investigated an anion-molecule S N Ar reaction in different solvents using explicit solvent (quantum mechanics/molecular mechanics methods, QM/MM) and the PCM method.…”

Section: Resultsmentioning

confidence: 99%

“…[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.…”

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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“…Nevertheless, many previous studies have indicated that this process has a very high activation barrier for neutral nucleophiles and is viable only for ionic nucleophiles. 21,[28][29][30][31][32][33][34] In the case of neutral nucleophiles, water molecules or a second nucleophile molecule can act as a catalyst. In the reaction of hydroxylamine with phenylacetate, we found a similar situation.…”

Section: Direct Hydroxylamine Attack Leading To a Neutral Tetrahedralmentioning

confidence: 99%

Dual bifunctional catalysis and the α-effect in the reaction of hydroxylamine with phenylacetate

Mazera

Pliego

Almerindo

et al. 2011

J. Braz. Chem. Soc.

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A reação da hidroxilamina com acetato de fenila foi investigada teoricamente para se obter uma melhor compreensão do efeito alfa nas reações de nucleófilos neutros. Os cálculos foram feitos em nível B3LYP/6-311+G(2df,2p)//HF/6-31G(d) incluindo o solvente (água) em nível PCM/HF/6-31G(d). Os resultados mostram que um ataque direto da hidroxilamina leva a uma barreira de energia livre de ativação DG ‡ muito alta, em torno de 50 kcal mol -1. Uma segunda molécula de hidroxilamina pode catalisar o processo através de catálise bifuncional usando ambos os grupos NH 2 e OH simultaneamente. Esta catálise bifuncional reduz o DG ‡ para 19 kcal mol -1 e é capaz de explicar a relação de produtos cinético e termodinâmico observada experimentalmente.The reaction of hydroxylamine with phenyl acetate was theoretically investigated to shed light on the role of catalysis and the origin of the a-effect in this system. Calculations at the B3LYP/6-311+G(2df,2p)//HF/6-31G(d) level and the solvent effect included at the PCM/HF/6-31G(d) level predict that the direct attack of hydroxylamine to the carbonyl centre has a high DG ‡ barrier, close to 50 kcal mol -1. A second hydroxylamine molecule can catalyse the process through bifunctional catalysis using both the NH 2 and OH groups simultaneously. This dual bifunctional catalysis decreases the DG ‡ to 19 kcal mol -1 and is able to explain the experimentally observed kinetics and product ratio.

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A Theoretical Analysis of the Free-Energy Profile of the Different Pathways in the Alkaline Hydrolysis of Methyl Formate In Aqueous Solution

Cited by 67 publications

References 19 publications

New insights on reaction pathway selectivity promoted by crown ether phase-transfer catalysis: Model ab initio calculations of nucleophilic fluorination

New insights on reaction pathway selectivity promoted by crown ether phase-transfer catalysis: Model ab initio calculations of nucleophilic fluorination

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

Dual bifunctional catalysis and the α-effect in the reaction of hydroxylamine with phenylacetate

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