Figure 11.

(a) Effect of angle of approach of substrate (Sub) to Cpd I on barrier to aliphatic and aromatic hydroxylation. Optimal orbital overlap leads to low barrier when angle of approach is approximately 130° (green). At larger angles of approach, non-optimal orbital overlap occurs, leading to higher barriers (red). (b) Orbital energy diagram for the first electron transfer step in the oxidation of substrate by Cpd I. The electron may transfer to either of the two singly occupied Fe–O π* orbitals.