The reaction not found by either meta-MD parameter sets. The reaction energy is ∆E = 19 kcal/mol and the barrier is ∆E † = 27 kcal/mol calculated with ωB97X-D3/def2-TZVP where D max,i is the maximum distance between any two atoms in molecule i. The coordinates of the reactants are energy minimised with GFN2-xTB before starting the meta-MD. If a change in atomic connectivity is detected the meta-MD simulation is skipped and the barrier estimation is done using the unoptimised reactant structure. We perform 100 meta-MD simulations for each reactant unless otherwise noted. Our algorithm checks for changes in atomic connectivity every 5 ps and the simulation is stopped when this is detected. The output of the meta-MD simulations is then a list of all unimolecular reactions and a database of the reactant and product structures.