Theoretical Determination of Partition Coefficients

Jonathan W. Essex, Christopher A. Reynolds, W. Graham Richards

Research output: Contribution to journalArticlepeer-review

65 Citations (Scopus)


The free energy perturbation method, implemented within a molecular dynamics framework, has been used to calculate differences in log Ps between methanol, ethanol, and propanol partitioned between water and carbon tetrachloride. The calculated results agree with experiment to within 0.45 log P unit or about 3 kJ mol−1. The difference in log P between methanol and ethanol was determined relatively easily. However, difficulties were experienced in extending the calculations to include the more flexible propanol molecule. A systematic variation of parameters was performed which highlighted the reason for the poor results, namely, the failure of the atomic charges to give a good description of the electrostatics in all conformations. This problem was overcome by using charges derived from the molecular electrostatic potential (MEP) for each conformation, weighted according to the appropriate Bolzmann population. It is proposed that these multiple conformation MEP derived charges will be useful in many other applications.

Original languageEnglish
Pages (from-to)3634-3639
Number of pages6
JournalJournal of the American Chemical Society
Issue number10
Publication statusPublished - 1 May 1992
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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