Prediction of heat of formation for exo-Dicyclopentadiene

Dicyclopentadiene (DCPD) is an organic compound with two structural isomers, the exo and endo isomers. There have been several thermal runaway accidents related to this hazardous compound. It is well known that heat of formation is one of the most important parameters to investigate thermal runaway reactions. The heat of formation for the endo isomer has been characterized via computational and experimental studies. However, there is no thorough computational or experimental study on the heat of formation for the exo isomer. In this work, computational chemistry methods with homodesmotic reaction schemes were proposed to predict the heat of formation for the exo isomer. First, the computational methodology was validated by comparing predicted results of the endo isomer with its existing experimental value (42.2 ± 0.6 kcal/mol). The results from high level ab-initio, density functional theory, and composite methods were shown in a good agreement with the experimental value. The same methodology was then applied to predict the heat of formation for the exo isomer. The energy difference of heat of formation between two isomers was estimated at 0.7 ± 0.1 kcal/mol based on various computational methods. Therefore, combining the experimental and computational data, the predicted heat of formation for the exo isomer is 41.5 ± 0.6 kcal/mol. This work could provide reliable thermochemical data for inherently safer design of any processes involving DCPD.