Stability of like and oppositely charged organic ion pairs in aqueous solution

Kyoung Tai No, Ky Youb Nam, Harold A. Scheraga

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66 Citations (Scopus)


To investigate the stability of ionic pairs in aqueous solution, polarizable continuum-model (PCM) ab initio molecular orbital calculations were carried out. Ion pairs formed from three organic ions, methylacetate, methylammonium, and guanidinium, were treated. The methylacetate ion pair forms a stable complex when the two methyl groups are in contact. When the charged groups of methylacetate and methylammonium are in contact, this pair does not form a stable complex in aqueous solution. When the methyl group of methylacetate is in contact with that of methylammonium, the ionic groups are far apart, and a stable complex is not formed, even though the complex involves a strong attractive electrostatic interaction. The guanidinium pair forms a stable complex in aqueous solution at all conformations investigated in this work even though a strong repulsive electrostatic interaction is present in this complex.

Original languageEnglish
Pages (from-to)12917-12922
Number of pages6
JournalJournal of the American Chemical Society
Issue number52
Publication statusPublished - 1997 Dec 31

All Science Journal Classification (ASJC) codes

  • Catalysis
  • General Chemistry
  • Biochemistry
  • Colloid and Surface Chemistry


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