Calculating virtual log P in the alkane/water system (log P(N)(alk)) and its derived parameters deltalog P(N)(oct-alk) and log D(pH)(alk).

Growing interest in the use of both the logarithm of the partition coefficient of the neutral species in the alkane/water system (log P(N)(alk)) and the difference between log P(N)(oct) (the logarithm of the partition coefficient of the neutral species in the n-octanol/water system) and log P(N)(alk) (Deltalog P(N)(oct-alk)) in the early stages of drug design has stimulated development of a computational tool based on the Volsurf software to predict virtual (=of each conformer) log P(N)(alk) and virtual log P(N)(oct). From these two pieces of data, it is then possible to calculate Deltalog P(N)(oct-alk) for a given compound as the difference between log P(N)(oct) and log P(N)(alk). Once the pK(a) is known and the legitimacy of neglecting the contribution made by the ionized species has been checked, it is also possible to calculate log D(pH)(alk), which might be an important lipophilicity descriptor in absorption, distribution, metabolism, and excretion (ADME) prediction, from log P(N)(alk).