THE POLAR EFFECT IN THE REACTION OF PEROXY-RADICALS WITH CARBONYL-COMPOUNDS

Kinetic data on the reactions of peroxy radicals with aldehydes and ketones are analyzed in the framework of the parabolic model of the transition state. The activation energy of these reactions is described by the parameter br(e), where b is the square root of the force constant of the C-H bond attacked, and r(e) is the displacement of the hydrogen atom in the elementary act. This parameter equals 12.83 (RO2. + RCHO), 13.69 (RO2. + C6H5CHO), 11.76 (RC(O)O2. + RCHO), 13.53 (C6H5C(O)O2. + C6H5CHO), and 13.96 (k/mol)0.5 (RO2. + RC(O)R). The polar interaction makes an important contribution to the activation energy of this reaction, lowering it by 8.8 (RO2. + RCHO), 15.8 (RC(O)OO. + RCHO), and 13.0 kJ/mol (RO2. + ketone). The reaction of RO2. with the C-H bond of hydrocarbons is used as a reference reaction.