On the nature of the tetrahedral species in the gas phase hydrolysis of esters

Takashima, Keiko; José, Sonia Maria; Amaral, Antônia Tavares do; Riveros, José M.

doi:10.1039/c39830001255

Cited by 25 publications

(24 citation statements)

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“…The total energy of 7 was calculated to be -342.168 13 ( -343.326 05) Hartree and is more stable than 2 by 31.5 (27.8) kcal mol-'. 7 is also more stable than the final products, 5 and 6, by 18.0 (17.2) kcal mol-I. This energy corresponds to the hydrogen bond energy between methanol and acetate ion.…”

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confidence: 92%

“…As it was very difficult to detect the T D intermediate in the gas phase reaction, Takasima et al suggested that it was more likely a local transition state than a stable intermediate. 5 Later, they proposed the path B which includes hydrogenbonded carboxylate-methanol species as another intermediate from their gas-phase experiment with CF,COOCH, and OH-.6 They postulated an extremely high barrier on the basis of the crude molecular orbital (MO) calculations by Alagona et al ' Johlman et al have performed a detailed analysis of the gas-phase reaction of methyl formate.' Quantum mechanical calculations indicated the existence of the stable T D intermediate.…”

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confidence: 99%

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Theoretical study of a reaction path via a hydrogen-bonded intermediate for the alkaline hydrolysis of esters in the gas phase

Hori¹

1992

J. Chem. Soc., Perkin Trans. 2

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T w o steps are considered for the alkaline hydrolysis of methyl acetate in the gas phase. The first step is the formation of a tetrahedral intermediate and the second is its decomposition. In the present paper, the mechanism for the second step is discussed by using ab initio molecular orbital calculations. The path releasing acetic acid and methoxide anion is an energetically unfavourable path, as easily expected by their pK, values. The final products, acetate ion and methanol, are more stable than the tetrahedral intermediate. We found a hydrogen-bonded acetate-methanol molecule as the intermediate that was more stable than both the tetrahedral intermediates and the final products. We searched and found the transition state which connected the tetrahedral intermediate with the hydrogen-bonded intermediate. The activation energy of the path through the transition state was calculated to be 8.7 kcal mol-' (MP2/6-31 + G**//RHF/6-31 G: 5.8). This mechanism explains well the alkaline hydrolysis of esters in the gas phase.Alkaline hydrolysis of esters is one of the most fundamental reactions in organic chemistry. The reaction mechanism in solution has been well studied' and is considered to be very simple as described in many text books.

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confidence: 92%

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confidence: 99%

Theoretical study of a reaction path via a hydrogen-bonded intermediate for the alkaline hydrolysis of esters in the gas phase

Hori¹

1992

J. Chem. Soc., Perkin Trans. 2

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“…11 These competitive processes were a subject of numerous investigations and were observed particularly in the gasphase reactions of esters. 4,6,7,[12][13][14][15][16][17][18] In some cases a nucleophilic attack on an alkyl group of the ester was observed, especially in the case of methyl esters. Such a phenomenon was observed by Takashima and Riveros during the reaction of a labeled hydroxyl anion with methyl formate, performed using Fourier transform ion cyclotron resonance spectrometer.…”

Section: Introductionmentioning

confidence: 99%

Reactions of Stabilized Aliphatic Carbanions with Esters of Formic Acid in the Gas Phase

Wileńska

Świder

Danikiewicz

2015

Eur J Mass Spectrom (Chichester)

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The reactions of nitromethane, acetonitrile, and ethyl acetate carbanions with formic acid esters were investigated in the gas phase by mass spectrometry and quantum chemical calculations. It was found that the carbanion of nitromethane practically does not react with formic acid esters and only traces of the Claisen- type addition-elimination reaction product were observed. In the case of the deprotonated acetonitrile, the Claisen-type condensation that yielded the carbanion of cyanoacetaldehyde proceeded almost quantitatively for all the studied formates. Other products, like the Riveros reaction product, were observed in minor amounts. The ethyl acetate carbanion reacts with formates in a much more complex way because it decomposes in a collision cell, yielding the deprotonated ketene anion, which also can react with formic acid esters. Consequently, the Claisen condensation reaction products of both anions were observed as well as the products of other reactions. All the proposed reaction pathways were confirmed by quantum chemical calculations, including the transition-state energies.

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“…These studies have revealed the interesting observation that OH − attack at the carbonyl position is not always the preferred mode of reaction in the gas‐phase. However, the question as to whether the tetrahedral species is indeed a stable species in the gas‐phase could not be directly established from these experiments24. On the theoretical side, calculations at different levels of theory have contributed significantly toward a full description of the OH − /ester reactions in vacuo25–33.…”

Section: Introductionmentioning

confidence: 99%

Gas‐phase acylium ion transfer reactions mediated by a proton shuttle mechanism

Fileti

Oliveira

Morgon

et al. 2011

Int J of Quantum Chemistry

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ABSTRACT:The mechanism and the energy profile of the gas-phase reaction that mimics esterification under acidic conditions have been investigated at different levels of theory. These reactions are known to proceed with rate constants close to the collision limit in the gas-phase and questions have been raised as to whether the typical addition-elimination mechanism via a tetrahedral intermediate can explain the ease of these processes. Because these reactions are common to many organic and biochemical processes it is important to understand the intrinsic reactivity of these systems. Our calculations at different levels of theory reveal that a stepwise mechanism via a tetrahedral species is characterized by energy barriers that are inconsistent with the experimental results. For the thermoneutral exchange between protonated acetic acid and water and the exothermic reaction of protonated acetic acid and methanol our calculations show that these reactions proceed initially by a proton shuttle between the carbonyl oxygen and the hydroxy oxygen of acetic acid mediated by water, or methanol, followed by displacement at the acylium ion center. These findings suggest

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On the nature of the tetrahedral species in the gas phase hydrolysis of esters

Cited by 25 publications

References 2 publications

Theoretical study of a reaction path via a hydrogen-bonded intermediate for the alkaline hydrolysis of esters in the gas phase

Theoretical study of a reaction path via a hydrogen-bonded intermediate for the alkaline hydrolysis of esters in the gas phase

Reactions of Stabilized Aliphatic Carbanions with Esters of Formic Acid in the Gas Phase

Gas‐phase acylium ion transfer reactions mediated by a proton shuttle mechanism

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