This study is based on Research and Education (R&E) project in Goksung high school. Energy flow and C？H and C？Cl bond dissociations in o-chlorotoluene(OCT) in collision with N2 is studied using classical trajectory procedures. The energy loss by the vibrationally excited OCT is small, but it increases with increasing total vibrational energy content ET of OCT between 5000 cm-1 and 30000 cm-1. Intermolecular energy transfer occurs mainly through vibration-translation(V？T) and vibration-vibration(V？V) pathways. The intramolecular energy flow between C？H and C？Cl stretching vibration in highly excited OCT (60000 ？ 60300 cm-1) leads to bond dissociation. The probabilities of C？H and C？Cl bond dissociation are 10-5~10-1 and increase exponentially with increasing vibrational excitation of OCT. On the other hand, the dissociation time of C-Cl bond is longer than that of C-Hmethylbond.