The data used for the experiments are available as .txt files. As many control measurements were carried out, there are often more data in the files than was used for analysis.  The data were measured using a PTR-ToF 6000 X2 (Ionicon Analytik GmbH, Innsbruck, Austria). The data obtained from these measurements were analysed using PTR-ToF-MS Viewer software (version 3.4.4.22, Ionicon Analytik GmbH) and saved as a .txt file. The butanone product ion signal (C₄H₉O⁺) was normalised to a reagent ion signal of 10⁶ ions per second.