The reaction pathway was also investigated by density functional theory (DFT), employing the SMD/B3LYP-D3/def2-TZVP//SMD/B3LYP-D3/6-31G(d) level of theory in o-DCB (for details, see the SI). Figure illustrates the energy profile for 1octen-3-ol (1a) substrate at 120 C (393 K). Catalyst 3j serves as the acid-base catalyst in the steps preceding the Claisen rearrangement (Figure ). The computed mechanism highlights the dual role of the carboxylate/carboxylic acid in synchronous proton transfer events in both TS a 1a-4a and TS a 4a-5a. The MOP ether intermediate ( ) is the most stable species prior to the product 6a, which is consistent with experimental data (Scheme 6) indicating a rapid buildup of [4a] in the reaction mixture. Finally, 5a undergoes a Claisen rearrangement to yield the final product 6a. For 5a, this step does not have the highest barrier, but this situation is reversed with other substrates (see Table ). For example, the final rearrangement step TS5p-6p has a barrier that is 2.7 kcal/mol higher in energy than the corresponding TS5a-6a. This result is in excellent agreement with the experimental results (Scheme 6) which clearly show that the reactivity difference between substrates 1a and 1p is due to the ultimate Claisen rearrangement step.