Kinetics and products of the reactions of OH radicals with 2-methyl-2-pentanol and 4-methyl-2-pentanol

Abstract

Kinetics and products of the gas-phase reactions of OH radicals with 2-methyl-2-pentanol and 4-methyl-2-pentanol were investigated. Using a relative rate method, rate constants for the gas-phase reactions of OH radicals with 2-methyl-2-pentanol and 4-methyl-2-pentanol of (7.93±0.58)×10 −12 cm 3 molecule −1 s −1 and (1.91±0.10)×10 −11 cm 3 molecule −1 s −1, respectively, were measured at 298±2 K, where the error limits are two standard deviations and do not include the uncertainty (estimated to be ∼±10%) in the rate constant for the reference compound. Gas chromatographic analyses showed the formation of acetaldehyde, propanal, acetone and 2-pentanone from the 2-methyl-2-pentanol reaction in the presence of NO, with molar formation yields of 22±3, 35±4, 56±6 and 5.4±1.1%, respectively. From the 4-methyl-2-pentanol reaction, gas chromatographic analyses showed the formation of acetaldehyde, acetone, 2-methyl-2-propanal and 4-methyl-2-pentanone, with molar formation yields of 37±6, 26±3, 11.1±1.2 and 25±2%, respectively. In situ atmospheric pressure ionization mass spectrometry analyses showed the formation of molecular weight 163 and 179 nitrates (attributed to hydroxynitrates and dihydroxynitrates, respectively) from both reactions, and the sum of the hydroxynitrate and dihydroxynitrate yields were determined to be ∼8% from the 2-methyl-2-pentanol reaction and ∼7% from the 4-methyl-2-pentanol reaction. Reaction mechanisms leading to the observed products are discussed and presented.