Figure shows the peroxy radicals studied in this work, which correspond to the three most predominant hydrogen abstractions that isobutanol can undergo. The alkoxy radical formed from hydrogen abstraction of isobutanol by OH is expected to be much less common and is not included in this work. For each of the three isomers studied, various unimolecular reactions can occur, as shown in Figure Previous quantum calculations of these important radicals have mostly focused on βRO 2 , since it is also formed in the OH-initiated oxidation of isobutene. Sun et al. and Lizardo-Huerta et al. report high-pressure-limit rates obtained from CBSQ//B3LYP/6-31G(d,p) and CBS-QB3, respectively. Similar work has not been conducted for the other two isomers, αRO 2 and γRO 2 , but studies on similar species have been done. Zádor et al. have studied the fate of the α-peroxy radical derived from ethanol, though the full surface of αRO 2 derived from isobutanol has not, to our knowledge, been evaluated. Welz et al. calculated a potential energy surface for the γRO 2 isomer, but did not include reactions of all isomers nor report reaction rates. Given the errors for isobutanol models at low temperature, and the lack of quantum calculations for the peroxy intermediates, we present thermodynamic and kinetic parameters for isomers, reactants, and products on the α-, β-, and γ-isobutanol peroxy surfaces. Since there is potential for some for these reactions to be dependent on pressure, both pressure-dependent and high-pressure-limit rate coefficients are reported. Comparison to other work and sensitivity analysis are conducted to determine the robustness of the rates.