Shenfeng Yuan

Mechanistic insights into the reaction of CF3CCl3 with SO3: Theory and experiment

Reaction mechanism of 1,1,1-trifluorotrichloroethane (CF3CCl3) and sulphur trioxide (SO3) in the presence of mercury salts (Hg2SO4 and HgSO4) was studied applying the density functional theory (DFT) at the UB3LYP/6-31+G(d,p) level. It was found that this reaction occurs in the free radical chain path as follows: mercury(I) sulphate free radical is generated by heat, causing CF3CCl3 to produce the CF3CCl2 free radical which reacts with SO3 leading to the formation of CF3CCl2OSO2 decomposing into CF3COCl and SO2Cl. The SO2Cl free radical triggers CF3CCl3 to regenerate CF3CCl2 which recycles the free radical growth reaction. This elementary reaction has the highest energy barrier and it is therefore the rate control step of the whole reaction path. Experiment data can confirm the existence of the mercury(I) salt free radical and the free radical initiation stage. So, mercury salts play the role of initiators not that of catalysts. The results agree well with our hypothesis.