The second set, PhEthOH, is the first set additionally supplemented with aromatic compounds, and comprises 200 molecules with a total of 7,185 atoms. Chemically, the difference in these sets is that PhEthOH includes aromatic rings, along with alkanes, ethers, and alcohols. AlkEthOH has one atom type not found in PhEthOH, namely H3, corresponding to a hydrogen bound to a carbon which is connected to three electron withdrawing groups. The aromatic groups in PhEthOH introduce two atom types not found in AlkEthOH -specifically, CA for aromatic carbons and HA for the hydrogens connected to those carbons. However, PhEthOH has more bond, angle, and fragment types than AlkEthOH.