THE MLP CALCULATION

The virtual logP (9) values obtained using the default MLP atomic parameters (8), have a too high average error ( logP = 0.66) compared to experimental measures. This divergence was probably due to the inaccurate parametrization of benzodioxane oxygens that are too hydrophilic and/or methoxylic oxygens that are too hydrophobic. The new benzodioxane parametrization is made comparing the experimental logP values of not-substituted benzodioxane (logP = 2.01) to tetraline (logP = 3.49) and calculating the correct oxygen atomic value with the following equation:

The different contribution of benzodioxane oxygen -substituted is obtained subtracting the already known atomic contributions from the experimental logP of the A2 (logP = 1.325), as shown in the following chart:

The comparison of experimental logP for A3, A8 and A10 derivatives shows that the contribution of methoxylic group is not constant and can be neglected. For this reason the oxygen atomic value is made equal to CH₃ contribution with opposite sign (f_O = -0.63).
The new parametrization gives a lower average error ( logP = 0.3) and shows the good enhancement of corrected oxygen contributions.