The gas phase ozonolysis and secondary OH production of cashmeran, a musk compound from fragrant volatile chemical products

Abstract

Fragrant personal care products are a subset of volatile chemical products (VCPs), an emerging source of outdoor pollutants capable of impacting air quality. Fragrant molecules, such as musks, are used in perfumes and have been found in aquatic organisms, water bodies, indoor air, and urban environments. Considering the distribution of musk-smelling compounds, there is a need to constrain their atmospheric fate indoors and outdoors. Here, we used a Vocus proton-transfer-reaction time-of-flight mass spectrometer to quantify the atmospheric oxidative fate of cashmeran, a bicyclic musk compound, detected in a commercial perfume alongside galaxolide, astratone and rosamusk. Cashmeran concentrations rose up to 0.35 ppbv representing a mass yield of 0.33 ± 0.04% of the perfume. We determined the second order rate constant of the cyclo-addition of O₃ with cashmeran to be (2.78 ± 0.31) × 10⁻¹⁹ cm³ molec⁻¹ s⁻¹ at 293 ± 1 K in N₂. This rate constant corresponds to an 85 day lifetime against 20 ppbv of O₃. Then, we repeated the ozonolysis experiments in air with 20% O₂ and measured significant secondary OH concentrations up to 5.1 × 10⁵ molec cm⁻³. Consequently, the lifetime of cashmeran in our experiment was shortened to 5 h. Thus, the oxidation of fragrant molecules, like cashmeran, could alter the oxidative capacity of indoor air via the production of secondary OH radicals. Furthermore, our results show that cashmeran is long-lived and could serve as a VCP tracer in urban air.