A general structure-property relationship to predict the enthalpy of
vaporization at ambient temperatures
Öberg, T.
Presentation vid the 12th International Workshop on Quantitative
Structure-Activity Relationships in Environmental Toxicology. Lyon, Frankrike,
8-12 maj, 2006.
Abstract
The vapor pressure is the most important property of an anthropogenic organic
compound in determining its partitioning between the atmosphere and the other
environmental media. The enthalpy of vaporization quantifies the temperature
dependence of the vapor pressure and its value around 298 K is needed for
environmental modeling. The enthalpy of vaporization can be determined with
different experimental methods, but estimation methods are needed to extend the
current database and several approaches are available from the literature.
However, these methods have limitations such as; a need for other experimental
results as input data, a limited applicability domain, a lack of domain
definition, or a lack of predictive validation. Here we have attempted to
develop a quantitative structure-property relationship (QSPR) that has a general
applicability and that is thoroughly validated. Enthalpies of vaporization at
298 K were collected from the literature for 1,835 pure compounds [1]. The three
dimensional (3D) structures were generated and each compound was described by a
set of computationally derived descriptors. The compounds were randomly assigned
into a calibration set and a prediction set. Partial least squares regression (PLSR)
was used to estimate a low-dimensional QSPR model with 12 latent variables. The
predictive performance of this model, within the domain of application, was
estimated at; Q^2 = 0.968 and SEP = 0.028 (log transformed values). The QSPR
model was subsequently applied to a database of 100,000+ structures, after a
similar 3D optimization and descriptor generation. Reliable predictions can be
reported for compounds inside of the previously defined applicability domain.
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