Thermal decomposition of the perfluorinated peroxides CF3OC(O)OOC(O)F and CF3OC(O)OOCF3.
Gas phase thermal decomposition of CF(3)OC(O)OOC(O)F and CF(3)OC(O)OOCF(3) was studied at temperatures between 64 and 98 degrees C (CF(3)OC(O)OOC(O)F) and 130-165 degrees C (CF(3)OC(O)OOCF(3)) using FTIR spectroscopy to follow the course of the reaction. For both substances, the decompositions were studied with N(2) and CO as bath gases. The rate constants for the decomposition of CF(3)OC(O)OOC(O)F in nitrogen and carbon monoxide fit the Arrhenius equations k(N)2 = (3.1 +/- 0.1) x 10(15) exp[-(29.0 +/- 0.5 kcal mol(-1)/RT)] and k(CO) = (5.8 +/- 1.3) x 10(15) exp[-(29.4 +/- 0.5 kcal mol(-1)/RT)], and that for CF(3)OC(O)OOCF(3) fits the equation k = (9.0 +/- 0.9) x 10(13) exp[-(34.0 +/- 0.7 kcal mol(-1)/RT)] (all in units of inverted seconds). Rupture of the O-O bond was shown to be the rate-determining step for both peroxides, and bond energies of 29 +/- 1 and 34.0 +/- 0.7 kcal mol(-1) were obtained for CF(3)OC(O)OOC(O)F and CF(3)OC(O)OOCF(3). The heat of formation of the CF(3)OCO(2)(*) radical, which is a common product formed in both decompositions, was calculated by ab initio methods as -229 +/- 4 kcal mol(-1). With this value, the heat of formation of the title species and of CF(3)OC(O)OOC(O)OCF(3) could in turn be obtained as Delta(f) degrees (CF(3)OC(O)OOC(O)F) = -286 +/- 6 kcal mol(-1), Delta(f) degrees (CF(3)OC(O)OOCF(3)) = -341 +/- 6 kcal mol(-1), and Delta(f) degrees (CF(3)OC(O)OOC(O)OCF(3)) = -430 +/- 6 kcal mol(-1).
Burgos Paci
Maximiliano A
MA
INFIQC, Departamento de Físico Química, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
Argüello
Gustavo A
GA
García
Placido
P
Willner
Helge
H