Quasiclassical trajectory calculations of collisional energy transfer (CET) and rotational energy transfer from highly vibrationally excited propane to rare bath gases are reported. The calculations employed atom–atom pairwise-additive Lennard-Jones, Buckingham exponential and hard-sphere intermolecular potentials to examine the dependence of CET on the intermolecular potential and to establish a protocol for future work on larger alkane systems. The role of the torsional (internal) and molecular (external) rotors in the energy-transfer mechanism were investigated. Comparison of the results with our earlier work on ethane+neon systems (A. Linhananta and K. F. Lim, Phys. Chem. Chem. Phys., 1999, 1, 3467) suggests that the internal and external rotors play a significant role in the deactivation mechanism for highly vibrationally excited alkanes.