The catalytic effect of water in basic hydrolysis of methyl acetate: A theoretical study

Fredrik Hæffner, Ching Han Hu, Tore Brinck, Torbjörn Norin

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38 Citations (Scopus)

Abstract

Base catalyzed hydrolysis of methylacetate has been investigated at the ab initio MP2/6-31+G*//HF/6-31+G* level of theory. In the gas phase the B(AC)2-mechanism is favoured over the S(N)2-mechanism by 22 kJ mol-1 in the computed free energy of activation. Two water molecules were added to the tetrahedral intermediate and to the third transition state of the B(AC)2- mechanism to simulate specific solvation of the reacting species. One of the water molecules was found to take part in a water-assisted six-membered cyclic transition state. The polarized continuum solvent model (PCM) was applied to all the optimized geometries to simulate the aqueous bulk medium. The computed free energy of activation of the water-assisted second transition state is 14 kJ mol-1 lower than that of the corresponding non- assisted transition state. The B(AC)2-mechanism in aqueous solution is favoured over the S(N)2-mechanism by 56 kJ mol-1 in free energy of activation. The computed free energies of activation of the B(AC)2-mechanism in aqueous solution are in good agreement with experimental data.

Original languageEnglish
Pages (from-to)85-93
Number of pages9
JournalJournal of Molecular Structure: THEOCHEM
Volume459
Issue number1-3
DOIs
Publication statusPublished - 1999 Feb 8

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

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