To evaluate the general applicability of the WTMetaD-IB AL approach to other reaction mechanisms, we studied the methyl shift of 2,2-dimethylisoindene, leading to 1,2-dimethylindene, in the gas phase (R2, Fig. ). Rearrangement reactions play a significant role in synthetic organic chemistry, with methyl shift being a key step in the Meinwald rearrangement and the synthesis of meroterpenoids. 57 R2 has previously been studied experimentally in pentane, reporting an activation free energy (∆G ‡ ) of 29.2 ± 1.1 kcal mol -1 at 365.6 K and suggesting a concerted mechanism based on experimental and computed thermodynamic data. Since solvent is unlikely to influence the mechanism of this reaction, MLPs were trained only in the gas phase.