PULSE-RADIOLYSIS AND FOURIER-TRANSFORM INFRARED STUDY OF NEOPENTYL PEROXY-RADICALS IN THE GAS-PHASE AT 297-K

The ultraviolet absorption spectrum of the neopentyl peroxy radical (CH3)3CCH2O2, and the kinetics and products of its self reaction have been studied in the gas phase at 298 K. Absorption cross sections were quantified over the wavelength range 230-290 nm. The measured cross section at 250 nm was; sigma(CH3)3CCH2O2(250 nm) = (5.4 +/- 1.2) x 10(-18) cm2 molecule-1 Errors represent statistical (2-sigma) together with our estimate of potential systematic errors(15%). The kinetics of the decay of the UV absorption following the generation of the neopentyl peroxy radicals was complicated by the rapid decomposition of the (CH3)3CCH2O radicals formed in channel (4a). (4a) (CH3)3CCH2O2 + (CH3)3CCH2O2 --> (CH3)3CCH2O + (CH3)3CCH2O + O2 (4b) (CH3)3CCH2O2 + (CH3)3CCH2O2 --> (CH3)3CCHO + (CH3)3CCH2OH + O2 (5) (CH3)3CCH2O --> (CH3)3C + HCHO By measuring the yield of t-butyl peroxy radicals, the branching ratio k4a/(k4a + k4b) was determined to be 0.39 +/- 0.03. The rate constant for the self reaction of neopentyl peroxy radicals was k4 = (1.07 +/- 0.22) x 10(-12) cm3 molecule-1 s-1. Quoted errors represent 2-sigma. These results are discussed with respect to the available literature data.