Experimental Study of the Reactions of OH Radicals with Propane,n‐Pentane,and n‐Heptane over a Wide Temperature Range

The kinetics of the reactions of propane, n‐pentane, and n‐heptane with OH radicals has been studied using a low‐pressure flow tube reactor (P = 1 Torr) coupled with a quadrupole mass spectrometer. The rate constants of the title reactions were determined under pseudo–first‐order conditions, monitoring the kinetics of OH radical consumption in excess of the alkanes. A newly developed high‐temperature flow reactor was validated by the study of the OH + propane reaction, where the reaction rate constant, k₁ = 5.1 × 10^?17T^1.85exp(–160/T) cm³ molecule^?1 s^?1 (uncertainty of 20%), measured in a wide temperature range, 230–898 K, was found to be in excellent agreement with previous studies and current recommendations. The experimental data for the rate constants of the reactions of OH with n‐pentane and n‐heptane can be represented as three parameter expressions (in cm³ molecule^?1 s^?1, uncertainty of 20%): k₂ = 5.8 × 10^?18T^2.2exp(260/T) at T= 248–900 K and k₃ = 2.7 × 10^?16T^1.7exp(138/T) at T= 248–896 K, respectively. A combination of the present data with those from previous studies leads to the following expressions: k₁ = 2.64 × 10^?17T^1.93exp(–114/T), k₂ = 9.0 × 10^?17T^1.8 exp(120/T), and k₃ = 3.75 × 10^?16 T^1.65 exp(101/T) cm³ molecule^?1 s^?1, which can be recommended for k₁, k₂, and k₃ (with uncertainty of 20%) in the temperature ranges 190–1300, 240–1300, and 220–1300 K, respectively.