Fluorescence excitation spectra of CH₃CH₂CH₂O (n-propoxy) radicals and (CH₃)₂CHO (i-propoxy) radicals were obtained using a combined laser photolysis/laser-induced fluorescence (LIF) technique and the kinetics of reactions of these radicals with (1) O₂ as a function of temperature and with (2) NO₂ as a function of pressure have been determined.

Propoxy radicals were produced by excimer laser photolysis of the appropriate propyl nitrites at l = 351 nm. The spectra of the (A ¬ X) transitions show progressions of the CO-stretching vibration in the electronically excited states with spacings of the bands of (560 ± 10) cm^-1 for i-propoxy and (580 ± 10) cm^-1 for n-propoxy. Fluorescence spectra taken after excitation in the (4, 0) band at l = 340.1 nm (i-propoxy) and in the (1, 0) band at l = 342.4 nm (n-propoxy) show progressions of the CO-stretching vibration in the electronic ground state of (900 ± 60) cm^-1 for i-propoxy and (1000 ± 50) cm^-1 for n-propoxy.

The Arrhenius expressions for the reactions of n-propoxy and i-propoxy with O₂ have been determined to be k₁(n) = (1.4 ± 0.6) ´ 10^-14 exp (-(0.9 ± 0.5) kJ mol^-1/ RT) cm^-3 s^-1 and k₁(i) = (1.0 ± 0.3) ´  10^-14 exp (-(1.8 ± 0.4) kJ mol^-1/ RT) cm^-3 s^-1 in the range 218-313 K. The rate coefficients for the reactions of NO₂ with n-propoxy and i-propoxy at T = 296 K were found to be independent of total pressure with k₂(n) = (3.6 ± 0.4) ´ 10^-11 cm^-3 s^-1 (6.7-53 mbar) and k₂(i) = (3.3 ± 0.3) ´ 10^-11 cm^-3 s^-1 (6.7-106 mbar).