Gas-phase Experiments on the Reactivity and Fate of Short-Chain Fatty Acid Ethyl Ester Derivatives

Fatty acid ethyl esters (FAEEs) are a class of aroma chemicals that occur naturally in numerous plants and are known for their fruity odour. They are commonly added to food items, cosmetics, scented air fresheners, and cleaners to provide flavour or fragrance, to enhance sweetness perception, or to intensify other aromas. Additionally, they are potentially suitable as solvents and advanced biofuels and could help reduce dependence on fossil fuels.

FAEEs are therefore widely used in both indoor and outdoor environments. If the side chain is short, FAEEs are highly volatile and prone to be present in the ambient air. Especially in indoor environments with poor ventilation, cumulative human exposure can be substantial. In the gas phase, the main loss processes of FAEEs are likely the reactions with OH radicals and photolysis. Rate coefficients and photolysis parameters for these processes determine the atmospheric lifetime of the FAEEs and the degree to which indoor-outdoor-exchange is possible, as well as the production rate of potentially harmful secondary products. However, detailed knowledge of the degradation mechanisms and kinetics is scarce for many FAEEs.

Here, we report experimental data on the OH radical reactions and photolytic properties of ethyl butyrate and several branched derivatives (ethyl 2-methylbutyrate, ethyl isovalerate, isopropyl butyrate). Results are discussed in terms of their potential impact on air quality both indoors and out.