Theoretical Studies on the Reactions of 1,1,2,2,3,3,4-Heptafluorocyclopentane with Hydroxyl and Hydrogen Free Radicals

1,1,2,2,3,3,4-Heptafluorocyclopentane (F7A) has considerable potential to be a new halon replacement due to its environmental friendliness and low-toxicity. However, the reaction processes of F7A with hydroxyl and hydrogen free radicals, which are of great importance for investigating its fire suppression mechanisms, are still unclear. In this paper, ab inito and density functional theory are used to deduce the possible reaction pathways for the reactions of F7A with hydroxyl and hydrogen free radicals at the CCSD/cc-pVDZ//B3LYP/6-311++G (d,p) level of theory. Two distinct reaction pathways including ten elementary reaction channels for F7A with hydroxyl free radical, and five distinct reaction pathways including twenty elementary reaction channels for F7A with hydrogen free radical are investigated. The geometries, vibrational frequencies and reaction energy barriers are also determined. Based on the calculated results, the possible reaction mechanisms are proposed and discussed. The most feasible reaction channel for F7A with hydroxyl free radical is that leads to CH(OH) CH2(CF2)(3)+center dot F, and the most feasible reaction channel for F7A with hydrogen free radical is that leads to (CF2)(3)CH2CH center dot+HF. The study is helpful to further study its fire suppression mechanisms and promote it to be a new generation of halon replacement.