THE GAS-PHASE REACTIONS OF BENZYL RADICALS WITH O, O-3, AND NO3 - RATE, MECHANISM, AND UNIMOLECULAR DECOMPOSITION OF THE CHEMICALLY ACTIVATED BENZOXY RADICAL

The reactions of the benzyl radical with O, O-3, and NO3 are investiga ted in a discharge flow-reactor with mass spectrometric detection. For the rate coefficients of the latter two reactions, we obtain values o f 2.8.10(13) and 1.93.10(12) cm(3) mol(-1) s(-1), respectively (T appr oximate to 300 K, P approximate to 2 mbar). The main products for all three reactions are C6H6 and C6H5CHO with relative yields of 0.60/0.40 (M. Bartels, J. Edelbuttel-Einhaus, and K. Hoyermann, 22nd Int. Symp. on Combustion, p. 1041, The Combustion Institute, Pittsburgh 1988), 0 .37/0.66, and 0.23/0.77, respectively. These branching fractions are i nterpreted in terms of the unimolecular decomposition of an intermedia rily formed benzoxy radical, using statistical rate theory. The molecu lar data needed are calculated by quantum chemical methods. The verifi cation of the experimental branching fractions requires the assumption of a direct reaction channel leading from C6H5CH2O to C6H6. The natur e of this channel is still uncertain.