A reexamination of the pyrolysis of bis trifluoromethyl peroxide

Abstract

The literature results for the pyrolysis of bis trifluoromethyl peroxide are reexamined and compared with those for dimethyl peroxide. The thermochemistry yields the result that the 7r-bond energy in carbonyl fluoride is 96 f 10 kcal/mol compared to 74 kcal/mol for that in formaldehyde. Thermodynamic additivity contributions are derived for the C-(F)3(0) and O-(C)(F) groups. Some conclusions are drawn in relation to the oxidation of bdogeno methyl radicals and the chemistry of the atmosphere.

Thermochemistry of COF2 and Related Compounds

“…12 We later obtained results based on calculations that in some cases differed significantly from their work." Batt and Walsh estimated AfH0298(CF30) from the enthalpy of the reaction CF300CF3 F?…”

“…A discrepancy still remains between the calculated DH0298(CF30-H) and that derived by the group additivity method. 12 The group additivity calculation essentially assumes that the bond energy difference between a peroxy RO-OR and a hydroxyl RO-H linkage is constant regardless of the R group. Such an approximation is likely not justified when R = CF3 because of the unique electronic properties of this group.41 Thus, we recommend use of the calculated values of DH0298-(CF30-H) = 119.4 kcal mol-' 1°~11,32742 and ArH0298(CF30H) = -217.7 f 2 kcalmol-'.lJl All therecommended heatsofformation obtained here are summarized in Table 3.…”

Reactions of alkoxy and alkyl peroxy radicals

“…Group values are also derived thereby. Finally via a re-examination of the data for the pyrolysis of bis(trifluoromethy1) peroxide Batt andWalsh (1982, 1983) led to values of AH F(CF302) = -674.9 kJ mol-' and D(CF,-0,) = 204-2 kJ mol-' This bond strength is some 85 kJmol-I stronger than the corresponding D(CH,-O,). However, recent studies (Batt and Stewart 1985, unpublished) suggest that D(CF,-O,)= 149 kJmol-'.…”

“…An analysis of the data of for the results of the decomposition of bistrifluoromethyl peroxide (Batt andWalsh 1982, 1983) gives a value for kZ9 of 10'0'3*0'2 M-' S -' .…”

The reaction of photochemically generated CF3O radicals with CO

“…The advantage of using this reference reaction is that the recombination reaction takes place anyway and therefore no other substances need to be added. The concentration of the CF 3 O radicals was calculated using the following equation and the value for molecule given by Batt and Walsh [32] and confirmed by Turnipseed et al…”