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Vapour Pressures of Pure Liquid Organic Compounds


The vapour pressure (po) of an organic compound is one of the main factors controlling its equilibrium partitioning between the gas and condensed (aerosol) phases.

Here we provide three structure-based estimators for vapour pressure, courtesy of DDBST GmbH: first, that Nannoolal et al. (1) for boiling point coupled with the modified vapour pressure predictor of Moller et al. (2); second, the methods of Nannoolal et al. (1, 3) for both boiling point and vapour pressure; third, the method of Stein and Brown (4) for boiling point coupled with the the vapour pressure equation of Myrdal and Yalkowsky (5). Boiling points can alternatively be specified by the user.

The results, which include po of the liquid compound at 298.15 K, the enthalpy of vaporisation ΔHo(po) and the associated heat capacity change ΔCpo(po), can be used in E-AIM.


To estimate a vapour pressure:

  1. Draw the molecule and save the the results as either an MDL structure file (which has an extension .mol), or a CTC file (which has an extension .ctc). The free DDB Explorer Edition can be used to create the molecules.
  2. Enter the name of the compound in the first box below, and then the name and location of the structure file.
  3. Enter the boiling point of the compound at atmospheric pressure, if known. Otherwise, leave the box blank and the boiling point will be estimated.
  4. Specify the temperature for which you require the vapour pressure. Note that values of the thermodynamic properties will always be output for 298.15 K.
Compound name:
 
Structure file:
 
Boiling point (K):
 
Temperature (K):

Press here to estimate the vapour pressure:

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References

(1)  Y. Nannoolal, J. Rarey, D. Ramjugernath, and W. Cordes (2004) Estimation of pure component properties. Part 1. Estimation of the normal boiling point of non-electrolyte organic compounds via group contributions and group interactions. Fluid Phase Equilibria 226, 45-63.

(2)  B. Moller, J. Rarey, and D. Ramjugernath (2008) Estimation of the vapour pressure of non-electrolyte organic compounds via group contributions and group interactions. J. Molecular Liquids 143, 53-63.

(3)  Y. Nannoolal, J. Rarey, and D. Ramjugernath (2008) Estimation of pure component properties. Part 3. Estimation of the vapor pressure of non-electrolyte organic compounds via group contributions and group interactions. Fluid Phase Equilibria 269, 117-133.

(4)  S. E. Stein, and R. L. Brown (1994) Estimation of normal boiling points from group contributions. J. Chem. Inf. Comput. Sci. 34, 581-587.

(5)  P. B. Myrdal and S. H. Yalkowsky (1997) Estimating pure component vapor pressures of complex organic molecules. Ind. Eng. Chem. Res. 36, 2494-2499.

Notes

1.  The vapour pressure predictor of Moller et al. (2) is an extension of that of Nannoolal and co-workers (3), and yields more accurate results for compounds with low vapour pressures. Errors and limitations in the method of Moller et al., chiefly for molecules with large numbers of functional groups, have been rectified as described in the addendum.

2.  A test dataset of 45 compounds with very low liquid vapour pressures has been provided by the group at the Centre for Atmospheric Science at the University of Manchester, and is described here. They have also evaluated and compared the vapour pressure prediction methods on this page (see M. H. Barley and G. McFiggans, Atmos. Chem. Phys. 10, 749-767, 2010).