Temperature dependent kinetics and insights on the gas-phase products of the reaction between prenol and hydroxyl radicals

Unsaturated alcohols with two functional groups (C=C and OH), such as prenol, are gaining attention as potential second-generation biofuels. As demand for sustainable energy sources grows, increased use of prenol in biofuel applications could lead to additional atmospheric emissions contributing to secondary pollution and affecting air quality. As the OH radical is the major oxidant during daytime and is highly reactive toward organic compounds, the OH-initiated oxidation of prenol needs to be investigated. Therefore, the reaction of prenol with OH was studied in the atmospheric simulation chamber THALAMOS (THermally Regulated Atmospheric Simulation Chamber), under atmospheric pressure and in the temperature range 273–353 K. The temperature-dependent rate coefficient, measured by the relative method, follows the Arrhenius equation: $k_{\text{prenol}+\text{OH}}\left(273-353K\right)=\left(1.43\pm 0.28\right)\times {10}^{-11}\times \exp \left(\frac{691\pm 59}{T}\right)$ cm³ molecule⁻¹ s⁻¹. Our results were combined with literature data determined under combustion relevant temperatures, to provide the following expression: $k_{\text{prenol}+\text{OH}}\left(273-1290K\right)=1.46\times {10}^{-10}$ $\times {\left(\frac{T}{300}\right)}^{-2.18}$ + 1.14 $\times {10}^{-10}$ $\times \exp \left(\frac{-2961}{T}\right)$ cm³ molecule⁻¹ s⁻¹ which covers a wide range of temperatures under atmospheric, but also cold (273–353 K) and traditional combustion conditions (900–1290 K). In addition to kinetic measurements, the reaction mechanism was investigated through product analysis. The major oxidation products, formed predominantly via the OH addition pathway, were acetone with a yield of 97 %, glycolaldehyde, and formaldehyde, with minor traces of 2-hydroxy-2-methylpropanal. The H-atom abstraction was found to be less significant (<3 %), leading primarily to the formation of prenal. These findings were further supported by structure–activity relationship(SAR) calculations, which estimated the rate coefficient at room temperature and confirmed that the reaction proceeds mainly (∼97 %) via OH addition to the C=C double bond of prenol. To our knowledge, this work is the first determination of the Arrhenius equation over the temperature range 273–353 K for the reaction between prenol and hydroxyl radical.