While several aspects of isobutanol combustion chemistry have been studied in detail, such as the initial hydrogen abstraction by OH and the oxidation of its smaller oxidation products, accurate pressure-dependent kinetics of peroxy radicals formed in isobutanol combustion has not been fully developed nor incorporated into detailed models. This is in spite of some isobutanol studies showing that ignition delay is sensitive to peroxy radical reactions. Given the sensitivity of this fuel to equivalence ratio and pressure, the formation and fate of peroxy radicals can significantly impact ignition timing and multi-stage heat release. Peroxy radical chemistry is also expected to control the environmental fate of isobutanol emitted into the environment, since peroxy radicals are also key intermediates in atmospheric degradation processes.