Kinetics and mechanism of the atmospheric reactions of atomic chlorine with 1-penten-3-ol and (Z)-2-penten-1-ol: an experimental and theoretical study

Abstract

Smog chamber/GC techniques were used to investigate the atmospheric degradation of two unsaturated alcohols, 1-penten-3-ol and (Z)-2-penten-1-ol, by oxidation with chlorine atoms at atmospheric pressure of N₂ or air, as a function of temperature. The rate coefficients at 298 K were (units in cm³ molecule⁻¹ s⁻¹): (2.35 ± 0.31) × 10⁻¹⁰ and (3.00 ± 0.49) × 10⁻¹⁰ for 1-penten-3-ol and (Z)-2-penten-1-ol, respectively. The identified and quantified gas-phase products (with molar yields in brackets) were carbonyl compounds such as chloroacetaldehyde (33 ± 1%), propionaldehyde (39 ± 1%), acetaldehyde (8 ± 3%) and 1-penten-3-one (2%) from 1-penten-3-ol; and chlorobutyraldehyde (19 ± 1%), propionaldehyde (27 ± 1%), acetaldehyde (18 ± 2%) and (Z)-2-pentenal (36 ± 1%) from (Z)-2-penten-1-ol. A parallel theoretical study at the QCISD(T)6-311G**//MP2/6-311G** level was carried out to facilitate understanding of the reaction mechanism. Both the theoretical and experimental studies indicated that addition of Cl to the double bond of the unsaturated alcohol is the dominant reaction pathway, although the H-abstraction channel cannot be excluded. The atmospheric lifetimes of those unsaturated alcohols were calculated and the results are discussed.