The phenoxy radical: UV spectrum and kinetics of gas-phase reactions with itself and with oxygen

The kinetics of the gas-phase reactions of the phenoxy radical with itself and with oxygen were investigated using flash photolysis coupled to UV absorption spectrometry at 760 Torr, using N-2 as the buffer gas. The UV absorption spectrum of the radical, which was determined from 220 to 300 nm, exhibits two intense bands at 232 and 280 nm, with cross section values of 4.0 and 1.1 X 10(-17) cm(2) molecule(-1), respectively. The rate expression for the self-reaction was determined from 280 to 423 K: k(1)(T) = (1.34+/-0.16) X 10(-12) exp[(631+/-37)K/T] cm(3) molecule(-1) s-1. No reaction could be detected between the phenoxy radical and molecular oxygen, with an upper limit for the rate constant estimated at 2 X 10(-18) cm(3) molecule(-1) s(-1), for temperatures up to 500 K. (C) 1997 Elsevier Science B.V.