Photochemistry of long-lived [(CF3)2CF]2C C2F5 radicals

Abstract

Abstract The mechanism of the photodecomposition of the long lived radical [(CF3)2CF]2C C2F5 is explored by UV and ESR spectroscopy and quantum chemical calculations. The kinetics of the photodecomposition of [(CF3)2CF]2C C2F5 are investigated in a matrix of glassy and liquid hexafluoropropylene trimer at 77 and 300 K, respectively. The mechanism of [(CF3)2CF]2C C2F5 photodecomposition does not depend on the phase state of the matrix but differs from the thermal decomposition of the radical. Under UV light with λ CF3 bond of the perfluoro-ethyl group of [(CF3)2CF]2C C2F5 is broken. Thermal decomposition of the radical above 373 K occurs by breaking a CF CF3 bond in the perfluoro-isopropyl group. The experimental results are consistent with the calculated bond dissociation energies and UV–vis excitation spectra of the radical. Additional calculated C C BDEs for a number of fluorocarbon radicals show that radicals can be designed with very low C C BDEs for the generation of CF3 radicals.