Atmospheric chemistry of 3-methoxy-1-propanol and 3-methoxy-1-butanol: Kinetics with OH radicals and Cl atoms, identification of the end-products in the presence of NO, mechanisms and atmospheric implications

Abstract

The rate coefficients for the reactions of OH radicals and Cl atoms with 3-methoxy-1-propanol (3-M-1-POL) and 3-methoxy-1-butanol (3-M-1-BOL) in the gas-phase have been measured at (298 ± 2) K and atmospheric pressure. A conventional relative-rate technique was used to determine the rate coefficients: k1 (OH + 3-M-1-POL)= (2.15 ± 0.28) x 10−11, k2 (OH + 3-M-1-BOL)= (2.38 ± 0.31) x 10−11, k3 (Cl + 3-M-1-POL)= (2.66 ± 0.23) x 10−10 and k4 (Cl + 3-M-1-BOL)= (2.95 ± 0.27) x 10−10, all in units of cm3 molecule−1s−1. The present work provides the first kinetic study of the reactions of Cl atoms with 3-M-1-POL and 3-M-1-BOL, and of the reaction of OH radicals with 3-M-1-POL. The kinetic results are presented and compared with those calculated (kSAR) using the structure-reactivity relationship (SAR) method, and reactivity trends are discussed. Additionally, products identification under atmospheric conditions was performed for the first time for the reactions cited above in the presence of NO, using two sampling methods and GC-MS-FID. 3-methoxypropanal, methyl formate and glycolaldehyde were identified from the 3-M-1-POL + OH/Cl reactions, while 3-methoxybutyraldehyde, methyl acetate and glycolaldehyde, were identified from the 3-M-1-BOL + OH/Cl reactions. From these identified products, a general scheme of the reaction mechanisms is proposed. Finally, based on the kinetic results and radiative efficiencies (REs) of the titled compounds, a discussion on the atmospheric implications due to its emissions into the troposphere is also presented.