Ultraviolet absorption spectra and kinetics of acetonyl and acetonylperoxy radicals

Acetonyl radicals and acetonylperoxy radicals were produced by pulse radiolysis of gas mixtures with varying concentrations of CH3COCH3 and O2 in 1 atm of SF6 to initiate the reactions (1) F+CH3COCH3→HF+CH3COCH2, (2) 2CH3COCH2 → products, (3) CH3COCH2+O2(+M) → CH3COCH2O2(+M) and (4) 2CH3COCH2O2 → products.

The ultraviolet absorption spectrum of the acetonyl radical is composed of a fairly weak band centered at 315 nm and a stronger band in the range of 200–250 nm. The absorption cross section has been determined, σ(310 nm) = (8.73 ± 0.50) × 10−19 cm2 molecule−1. The values k2=(4.8 ± 0.4) × 10−11, k3=(1.5 ± 0.3) × 10−12 and k4=(8.3 ± 1.6) × 10−12 cm3 molecule−1 s−1 at 298 K were derived by computer modelling of the observed kinetic features.