UV SPECTRA AND KINETICS OF RADICALS PRODUCED IN THE GAS-PHASE REACTIONS OF CL, F AND OH WITH TOLUENE

The gas phase reactions of Cl, F and OH with toluene have been studied by pulse radiolysis combined with time-resolved UV spectroscopy. The formation of benzyl radicals via the abstraction reactions C6H5-CH3 + X --> C6H5-CH2 + HX was observed with X = Cl, F and OH. In the reaction with chlorine atoms the benzyl radical was the only reaction product observed. The addition reactions Y + C6H5-CH3 --> Y-C6H5-CH3 were observed with Y = F and OH, and the ultraviolet absorption spectra of the short-lived adducts have been recorded. Rate constants for the abstraction and addition reactions were derived from the observed formation kinetics and the relative yields of benzyl radicals and radical adducts, respectively. For the reaction of OH with toluene we have determined an overall rate constant for the addition and abstraction channels of k = (6.4 +/- 0.7) x 10(-12) cm3 molecule-1 s-1 and a branching ratio of 0.89 for the addition channel at 338 K.