Rate constants for the reaction of OH radicals with n-propyl acetate, sec-butyl acetate, tetrahydrofuran and peroxyacetyl nitrate

Abstract

Measurements of the rates of disappearance of n-propyl and sec-butyl acetates and of tetrahydrofuran, relative to that of isobutene, in irradiated NO x -hydrocarbon mixtures in air at 1 atmosphere total pressure in two environmental chambers (each of ≈6000-ℓ volume) have been used to derive relative rate constants for the reaction of the hydroxyl radical with these organics. Using a literature rate constant for the reaction of OH radicals with isobutene of 3.05 × 10 10 ℓ mole −1 s −1 the following absolute rate constants at 305 ± 2 K are obtained: ( k × 10 −9 ℓ mole −1 s −1) n-propyl acetate, 2.6 ± 0.5; sec-butyl acetate, 3.4 ± 0.7; tetrahydrofuran, 8.8 ± 1.8. In addition, a flash photolysis-resonance fluorescence technique has been used to obtain an upper limit of k ⩽ 1 × 10 8 ℓ mole −1 s −1 at 299 ± 1 K for the reaction of OH radicals with peroxyacetyl nitrate (PAN) which is structurally related to the acetates by the replacement of an alkyl group by an NO 3 group. The reactions of OH radicals with the ethers and acetates are fast and are discussed in terms of the effects of structure on reactivity, as well as their implications to assessments of hydrocarbon reactivity.