(Top) Evaluated mechanistic pathways for the reaction of a heme-peroxo-copper complex, LS-AN, with 4-OMe-phenol which proceed through one of two transition states, denoted TSpi for the proton-initiated mechanism and TShb for the hydrogen bond assisted pathway (see text for discussion). (Bottom) The potential energy surfaces for the PI and HB pathways. The red and blue lines in each plot correspond to the progress of the reaction leading to the products shown in the top, right, with the highest point on each surface being the transition state for each reaction. Dashed lines denote where the pathway is behind the surface. Adapted from ref 747. Copyright 2017 American Chemical Society.