Certain groups of molecules seem to be more challenging for log P predictions. Two of the most poorly predicted molecules, SM42 and SM43, are isoxazoles. Isoxazoles are oxygen and nitrogen-containing heteroaromatics. When we consider the calculated MAE of each molecule separated out by method category, we find that predictions for 2 out of the 3 molecules (SM41 and SM43) belonging to the isoxazole compound class are less accurate with MM-based physical methods than with QM-based physical and empirical method categories (Figure ).