THE ESR STUDY OF THE STRUCTURE AND REACTIVITY OF ALPHA-KETORADICALS DERIVATIVES OF (CF3)(3)CC(O)C(O)CF3

The structure and reactivity of alpha-ketoradicals, derivatives of (CF 3)(3)CC(O)C(O)CF3 (1), were studied by ESR spectroscopy. The photoredu ction of alpha-diketone 1 in a solution of cyclohexane in perfluorodip entyl ether results in the formation of radicals of two types, (CF3)(3 )CC(2)(O(4))C-.(3)(O(6)H)CF3 (1a) and (CF3)(3)(CC)-C-.(OH)C(O)CF3 (1b) in a similar to 40 : 1 ratio. The degree of delocalization of the spi n density in two conformers of radical la was calculated by the MNDO/P M3 method in the UHF approximation. It was established that radicals 1 a and 1b are capable of reversible dimerization. The rate constant of dimerization and the enthalpy of the radical-dimer equilibrium were me asured for radical 1a. A decrease in the rate of dimerization of radic al la upon addition of complexing solvents ((CF3)(3)COH and p-CF3C6H4C F3) was found. The influence of the solvents on the rate of dimerizati on was also detected for alpha-ketoradical (CF3)(3)CC(O)C-.(OSiMe2Ph)C F3 (1c).