ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

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

Zhi-Zheng Liu, Zhi-Rong Chen, Hong Yin, and Shen-Feng Yuan

Department of Chemical and Biochemical Engineering, Zhejiang University, Hangzhou, 310027 China

E-mail: yinh@zju.edu.cn

Abstract: 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.

Keywords: reaction mechanism – mercury salts – density functional theory – free radical chain

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-012-0205-8

Chemical Papers 66 (11) 1059–1064 (2012)