Justification on cyclopropene to propyne isomerization pathway based on vibrational calculations

We report a density-functional coupled with vibrational calculation on justifying the isomerization pathway of cyclopropene to propyne. The idea is to present the pathway in energy level diagram which the transition state is ensured by tracking a particular mode that supports the cyclic bond breaking and triple bond formation to occur. This mode decreases along the pathway and disappears at the transition state. To verify the designed pathway, the activation energy of the isomerization is used to find the rate constant with respect to experimental data at 500 K and 700 K by using transition state theory (TST). At those temperatures, TST predicts the rate constant at the same order of magnitude with the experimental result. It shows that the trend between calculation and experimental data is qualitatively in a good agreement, which implies that the designed pathway is justified. Furthermore, this study can be used as a guide if one needs to construct an isomerization pathway.