**J. Devillers**

*Estimating Octanol-Water Partition Coefficients with an
Autocorrelation/Neural Network Model*

`CTIS, 3 Chemin de la Graviere, 69140 Rillieux la Pape,
France. E-mail: jde-ctis@imaginet.fr`

A composite backpropagation neural network model (BNN) [1] was developed for calculating the n-octanol/water partition coefficient (log P) of molecules containing nitrogen, oxygen, halogen, phosphorus, and/or sulfur atoms. Chemicals were described by means of autocorrelation vectors encoding hydrophobicity, molar refractivity, H-bonding acceptor ability, and H-bonding donor ability. A 35/32/1 BNN constituted of four configurations was selected as final model (RMS = 0.37, r = 0.97) because it allowed to obtain the best simulation results (RMS = 0.39, r = 0.98) on an external testing set of 519 molecules. This final model compared favorably with different models based on atom/fragment contribution values and correction factors.

[1] Devillers, J. (1996). Neural Networks in QSAR and Drug Design. Academic Press, London, p. 284.

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