Photolysis of 1,1,1‐trifluoromethylazomethane as a source of methyl and trifluoromethyl radicals

Abstract

The photochemistry of 1 ,l , 1-trifluoromethylazomethane has been partially characterized. The quantum yield for Nz formation from photolysis at 366 nm and room temperature was unity at low pressure and decreased to 0.5 at 630 torr. At room temperature the principal products were C2H6, C2F6, CH3CF3 (or CHzCFz + HF at reduced pressures), plus substituted hydrazines, which mainly arise from addition of CF3 to the parent followed by combination of these radicals with CH3 or CF3. These fluorinated methyl hydrazine products detract from the general utility of CFa-N2-R compounds as sources for simultaneous study of the chemistry of CF3 and R radicals. At room temperature the hydrazine products accounted for more than 50% of the total yield; however, these products can be reduced by lowering the temperature and at 195°K their yields are negligible. The quantum yield for intramolecular (direct) formation of CH3CF3 + NZ was shown to be <0.002.

Collisional deactivation probabilities for chemically activated 1,1,1‐trifluoroethane

“…The difference in the two systems probably arises from loss of CH2=-CF2 by secondary reactions in the CF&OCH3 system, as has been previously found [7,8]. The chemistry associated with secondary reactions differs significantly in the two systems because of the rapid addition reaction of CF3 to CF3N2CH3 [5]. For present purposes the point to be made is that the results from the two photochemical systems confirm the overall validity of the high values of rate constants with Nz as the bath gas.…”

“…For several bath gases experiments were done at 300°K and 195°K. The important general conclusions are (a) there is a wide spread in collisional efficiencies for various bath gases, and (b) CH 3CF 3 is particularly difficult to deactivate relative to 1,2-dichloroethane [3] and cyclopropane [4].The photolysis [5] of CF3N2CH3 generates CH3 and CF3 radicals from which chemically activated CHBCF3" molecules are formed, with an average energy of 102 kcal/rnole [Z]. The critical energy for H F elimination producing CHz=CF2 is -68 kcal/mole [6].…”