The E-2 cluster (20 compounds, average TC = 0.2396) did not significantly differ from the E-1 cluster, except that the valley between the peaks derived from CH (CH2) near 2850 cm -1 was shallower. Simple aliphatic hydrocarbons with OH or double-bonded groups were also classified. As the E-2-2 cluster exhibited high similarity in the 700-1500 cm -1 region and was more complex than the E-2-1 cluster, it diverged from the A-2-1 cluster over a long distance.