Kinetics and Products of the Reactions of Ethyl and n -Propyl Nitrates with OH Radicals

Abstract

The kinetics of the reactions of ethyl (1) and n-propyl (2) nitrates with OH radicals has been studied using a low-pressure flow tube reactor combined with a quadrupole mass spectrometer. The rate constants of the title reactions were determined under pseudo–first-order conditions from kinetics of OH consumption in high excess of nitrates. The overall rate constants, k1 = 1.14 × 10−13 (T/298)2.45 exp(193/T) and k2 = 3.00 × 10−13 (T/298)2.50 exp(205/T) cm3 molecule−1 s−1 (with conservative 15% uncertainty), were determined at a total pressure of 1 Torr of helium over the temperature range (248–500) and (263–500) K, respectively. The yields of the carbonyl compounds, acetaldehyde and propanal, resulting from the abstraction by OH of an α-hydrogen atom in ethyl and n-propyl nitrates, followed by α-substituted alkyl radical decomposition, were determined at T = 300 K to be 0.77 ± 0.12 and 0.22 ± 0.04, respectively.