Mechanistic insights and atmospheric implications of the degradation reaction of 3-methoxy-1-propanol by reaction with hydroxyl radicals and identification of the end products in the presence of O/NO.

The study investigated the degradation of 3-methoxy-1-propanol (3M1P) by OH using the M06-2X/6-311++G(d, p) level, with CCSD(T) single-point corrections. We focused on hydrogen atom abstraction from various alkyl groups within the molecule. The rate coefficient for 3M1P degradation was calculated from the sum of the rate coefficients corresponding to the removal of H-atoms from primary (-CH), secondary (-CH-), tertiary (-CH< ), and alcohol (-ΟH) groups. The primary attack by hydroxyl radicals occurs at the hydrogen atom bonded to carbon atoms adjacent to the oxygen atom in the ether group, leading to the formation of alkyl radicals. The computed overall rate constant is 1.85 × 10 cm molecule sec at atmospheric pressure and room temperature, which is consistent with the experimental value of (2.15 ± 0.28)×10 cm molecule sec. This strong agreement confirms the reliability of the computational approach, which provides insights into the atmospheric reactivity and degradation pathways of 3M1P. The tropospheric lifetime of 3M1P is around 15 h, indicating rapid degradation in the atmosphere, potentially contributing to photochemical smog formation. The average ozone production from 3M1P emissions is ~ 2.1 ppb, with estimated photochemical ozone creation potential (POCP) values of 44 and 43 for north-west European and USA-urban conditions, respectively. These values indicate a moderate risk of photochemical smog production and potential harm to human health and the environment due to 3M1P emissions. Successive pathways involve the addition of molecular oxygen to the energized adducts [3M1P], forming [3M1P-O] peroxy radicals, which primarily react with nitric oxide to produce nitrogen dioxide and the [3M1P-O] alkoxy radicals. The major degradation products include methyl formate, 3-hydroxypropyl formate, glycolaldehyde, and 3-methoxypropanal.