To efficiently obtain accurate rate coefficients necessary for our analysis, we conducted geometry optimization, hindered rotor scans, and frequency calculations with B3LYP/CBSB7 or BMK/6-31g(d) on Gaussian 03 . Energy was calculated with CCSD(T)-F12/cc-pVTZ-F12 using either Molpro 2012.1.21 or Molpro 2015.1.37, including scaling the triples energy to the ratio of correlation energies from F12 and MP2. For each molecule and transition state, we first conducted a geometry optimization of an initial guess. Transition states were verified to have one imaginary frequency. Internal Reaction Coordinate (IRC) calculations were conducted at B3LYP/CBSB7 level theory and visualized to ensure the transition states correspond with the correct reactants and products (see ESI † for trajectories of each IRC calculation). For each rotatable dihedral, we calculated relaxed hindered rotor scans using 10-degree increments. In cases in which hindered rotor scans resulted in an unexpected reaction, hindered rotor scans were rerun with the fixed dihedral angles and bond lengths to prevent an undesired reaction from occurring. While most geometry, hindered rotor and frequency calculations used the B3LYP method, calculations for compounds with a hydroperoxy group on the α carbon used BMK because B3LYP had difficulty with these structures.