Concerted SN2 mechanism for the hydrolysis of acid chlorides

Comparisons of reactivities calculated by the density functional theory with experimental data

Ferenc Ruff, O. Farkas

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

DFT computations have been performed in acetone and water solvents in order to investigate the mechanism of hydrolysis of acid chlorides. Acetyl chloride and chloroacetyl chloride hydrolyze via concerted, one-step SN2 mechanism, with the attack of water at the sp2 hybridized carbon atom of the C=O group, and the transition state (TS) has distorted tetrahedral geometry. Solvent molecules act as general base and general acid catalysts. The TS of chloroacetyl chloride is tighter and less polar than the TS of acetyl chloride. The structure of the SN2 TS for the hydrolysis of benzoyl chlorides changes with the substituents and the solvent. Tight and loose TSs are formed for substrates bearing electron withdrawing (e-w) and electron donating (e-d) groups, respectively. In acetone, only the e-w effect of the substituents increase the reactivity of the substrates, and the change of the structure of the TSs with the substituents is small. In water, polar and very loose TSs are formed in the reactions of benzoyl chlorides bearing e-d substituents, and the rate enhancing effect of both e-d and e-w groups can be computed at higher level of theory. Calculated reactivities and the changes of the structure of the TSs with substituents and solvent are in accordance with the results of kinetic studies. In SN2 nucleophilic substitutions late/early TSs are formed if the attacking reagent is poorer/better nucleophile than the leaving group, and loose/tight TSs are formed for substrates bearing e-d/e-w substituents and in protic/aprotic solvents.

Original languageEnglish
Pages (from-to)480-491
Number of pages12
JournalJournal of Physical Organic Chemistry
Volume24
Issue number6
DOIs
Publication statusPublished - Jun 2011

Fingerprint

Density functional theory
hydrolysis
Chlorides
Hydrolysis
reactivity
chlorides
density functional theory
acids
Acids
Bearings (structural)
Electrons
electrons
Acetone
acetone
Water
Substrates
water
Nucleophiles
nucleophiles
Discrete Fourier transforms

Keywords

  • acid chlorides
  • DFT calculations
  • nucleophilic substitution
  • solvent effect
  • substituent effect

ASJC Scopus subject areas

  • Organic Chemistry
  • Physical and Theoretical Chemistry

Cite this

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title = "Concerted SN2 mechanism for the hydrolysis of acid chlorides: Comparisons of reactivities calculated by the density functional theory with experimental data",
abstract = "DFT computations have been performed in acetone and water solvents in order to investigate the mechanism of hydrolysis of acid chlorides. Acetyl chloride and chloroacetyl chloride hydrolyze via concerted, one-step SN2 mechanism, with the attack of water at the sp2 hybridized carbon atom of the C=O group, and the transition state (TS) has distorted tetrahedral geometry. Solvent molecules act as general base and general acid catalysts. The TS of chloroacetyl chloride is tighter and less polar than the TS of acetyl chloride. The structure of the SN2 TS for the hydrolysis of benzoyl chlorides changes with the substituents and the solvent. Tight and loose TSs are formed for substrates bearing electron withdrawing (e-w) and electron donating (e-d) groups, respectively. In acetone, only the e-w effect of the substituents increase the reactivity of the substrates, and the change of the structure of the TSs with the substituents is small. In water, polar and very loose TSs are formed in the reactions of benzoyl chlorides bearing e-d substituents, and the rate enhancing effect of both e-d and e-w groups can be computed at higher level of theory. Calculated reactivities and the changes of the structure of the TSs with substituents and solvent are in accordance with the results of kinetic studies. In SN2 nucleophilic substitutions late/early TSs are formed if the attacking reagent is poorer/better nucleophile than the leaving group, and loose/tight TSs are formed for substrates bearing e-d/e-w substituents and in protic/aprotic solvents.",
keywords = "acid chlorides, DFT calculations, nucleophilic substitution, solvent effect, substituent effect",
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T2 - Comparisons of reactivities calculated by the density functional theory with experimental data

AU - Ruff, Ferenc

AU - Farkas, O.

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Y1 - 2011/6

N2 - DFT computations have been performed in acetone and water solvents in order to investigate the mechanism of hydrolysis of acid chlorides. Acetyl chloride and chloroacetyl chloride hydrolyze via concerted, one-step SN2 mechanism, with the attack of water at the sp2 hybridized carbon atom of the C=O group, and the transition state (TS) has distorted tetrahedral geometry. Solvent molecules act as general base and general acid catalysts. The TS of chloroacetyl chloride is tighter and less polar than the TS of acetyl chloride. The structure of the SN2 TS for the hydrolysis of benzoyl chlorides changes with the substituents and the solvent. Tight and loose TSs are formed for substrates bearing electron withdrawing (e-w) and electron donating (e-d) groups, respectively. In acetone, only the e-w effect of the substituents increase the reactivity of the substrates, and the change of the structure of the TSs with the substituents is small. In water, polar and very loose TSs are formed in the reactions of benzoyl chlorides bearing e-d substituents, and the rate enhancing effect of both e-d and e-w groups can be computed at higher level of theory. Calculated reactivities and the changes of the structure of the TSs with substituents and solvent are in accordance with the results of kinetic studies. In SN2 nucleophilic substitutions late/early TSs are formed if the attacking reagent is poorer/better nucleophile than the leaving group, and loose/tight TSs are formed for substrates bearing e-d/e-w substituents and in protic/aprotic solvents.

AB - DFT computations have been performed in acetone and water solvents in order to investigate the mechanism of hydrolysis of acid chlorides. Acetyl chloride and chloroacetyl chloride hydrolyze via concerted, one-step SN2 mechanism, with the attack of water at the sp2 hybridized carbon atom of the C=O group, and the transition state (TS) has distorted tetrahedral geometry. Solvent molecules act as general base and general acid catalysts. The TS of chloroacetyl chloride is tighter and less polar than the TS of acetyl chloride. The structure of the SN2 TS for the hydrolysis of benzoyl chlorides changes with the substituents and the solvent. Tight and loose TSs are formed for substrates bearing electron withdrawing (e-w) and electron donating (e-d) groups, respectively. In acetone, only the e-w effect of the substituents increase the reactivity of the substrates, and the change of the structure of the TSs with the substituents is small. In water, polar and very loose TSs are formed in the reactions of benzoyl chlorides bearing e-d substituents, and the rate enhancing effect of both e-d and e-w groups can be computed at higher level of theory. Calculated reactivities and the changes of the structure of the TSs with substituents and solvent are in accordance with the results of kinetic studies. In SN2 nucleophilic substitutions late/early TSs are formed if the attacking reagent is poorer/better nucleophile than the leaving group, and loose/tight TSs are formed for substrates bearing e-d/e-w substituents and in protic/aprotic solvents.

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