Thermal decomposition of CF3OC(O)OOC(O)F and CF3OC(O)OOCF3

MAXIMILIANO A. BURGOS PACI; GUSTAVO A. ARGÜELLO; PLÁCIDO GARCÍA; HELGE WILLNER

JOURNAL OF PHYSICAL CHEMISTRY A

ACS

Lugar: Columbus; Año: 2005 vol. 109 p. 7481 - 7488

1089-5639

Gas phase thermal decomposition of CF3OC(O)OOC(O)F and CF3OC(O)OOCF3 was studied at temperatures between 64 and 98 °C (CF3OC(O)OOC(O)F) and 130-165 °C (CF3OC(O)OOCF3) using FTIR spectroscopyto follow the course of the reaction. For both substances, the decompositions were studied with N2 and COas bath gases. The rate constants for the decomposition of CF3OC(O)OOC(O)F in nitrogen and carbon monoxidefit the Arrhenius equations kN2 ) (3.1 ( 0.1) × 1015 exp[-(29.0 ( 0.5 kcal mol-1/RT)] and kCO ) (5.8 (1.3) × 1015 exp[-(29.4 ( 0.5 kcal mol-1/RT)], and that for CF3OC(O)OOCF3 fits the equation k ) (9.0 (0.9) × 1013 exp[-(34.0 ( 0.7 kcal mol-1/RT)] (all in units of inverted seconds). Rupture of the O-O bondwas shown to be the rate-determining step for both peroxides, and bond energies of 29 ( 1 and 34.0 ( 0.7kcal mol-1 were obtained for CF3OC(O)OOC(O)F and CF3OC(O)OOCF3. The heat of formation of the CF3-OCO2• 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 CF3OC(O)OOC-(O)OCF3 could in turn be obtained as ∆fH° (CF3OC(O)OOC(O)F) ) -286 ( 6 kcal mol-1, ∆f298H°(CF3OC(O)OOCF3) ) -341 ( 6 kcal mol-1, and ∆fH° (CF3OC(O)OOC(O)OCF3) ) -430 ( 6 kcal mol-1.