The acetyl radicals CH₃CO· and CD₃CO· studied by flash photolysis and kinetic spectroscopy

Ultraviolet absorption spectra have been characterized for the acetyl‐ h 3 and acetyl‐ d 3 radicals, which were generated by the flash photolysis of the corresponding acetones. The spectra are broad and intense, with values of the extinction coefficient at the respective maxima estimated as: ϵCH 3 CO(215) = (1.0 ± 0.1) × 10 4 L/mol·cm and ϵCD 3 CO(207.5) = (1.0 ± 0.05) × 10 4 L/mol·cm. Rate constants for the reactions of mutual interaction equation image were estimated as: k = 3.5 × 10 10 L/mol·s and k = 3.4 × 10 10 L/mol·s. Rate constants for the reactions of cross interaction equation image were estimated as: k = 8.6 × 10 10 L/mol·s and k = 5.2 × 10 10 L/mol·s. The related values of the cross interaction ratios k /( k k ) 1/2 = 2.6 and k /( k k ) 1/2 = 1.6 do not differ significantly from the statistical value of 2. The participation of the radical displacement reactions equation image was estimated in terms of the fractions k / k = 0.38 and k / k = 0.47. Corroborative spectra were obtained from the flash photolysis of methyl ethyl ketone and biacetyl, and the relative rates of the competing primary processes were estimated from the relative peak heights of the acetyl and methyl radicals in each system.