LIF spectra of n-propoxy and i-propoxy radicals and kinetics of their reactions with O2 and NO2

Article abstract of DOI:10.1002/bbpc.19981020502

Fluorescence excitation spectra of CH₃CF₂CH₂O (n-propoxy) 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 γ=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 λ=340.1 nm (i-propoxy) and in the (1,0) band at λ=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 ractions 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) cm³ s^-1 and k_t (i) = (1.0±0.3)×10^-14 exp (-(1.8±0.4) kJ mol^-1/RT) cm³ 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^-14 cm³ s^-1 (6.7-53 mbar) and k₂(i)=(3.3±0.3)×10^-11 cm³ s^-1 (6.7-106 mbar). WILEY-VCH Verlag GmbH, 1998.