Rate Constants of the Reactions of CF3O2, i‐C3H7O2 and t‐C4H9O2 with NO

The kinetics of the title reactions have been studied at T = 290 K and p = 2 Torr He using the fast‐flow technique combined with molecular‐beam sampling mass spectrometry. – In our novel approach, the total rate constant k1 of RO2 + NO → RO + NO2/RONO2 (1) is determined from the shape of the NO2‐growth profile. The validity of the method is demonstrated by the nearly identical results for k1, (CF3O2 + NO) obtained from CF3O2‐decays: k1 = (1.54 ± 0.35) · 10−11 and from NO2‐growths: k1 = (1.51 ± 0.4) · 10−11 cm3 s−1, in excellent agreement also with previous determinations. – Rate coefficient data of alkylperoxy + NO reactions, derived from NO2‐profiles, are reported for i‐C3H7O2 + NO: k1 = (5.0 ± 1.2) · 10−12 and for t‐C4H9O2 + NO: k1 = (4.0 ± 1.1) · 10−12 cm3 s−1. Our results, in combination with literature values for smaller peroxy radicals, indicate a marked decrease of the rate coefficient with increasing CH3‐substitution. Including data on haloalkyl‐ and acetylperoxy reactions, the reactivity of RO2 towards NO is shown to correlate with the electron acceptor/donor properties of substituents on the α‐carbon.