The buildup kinetics of the main and side products during uncatalyzed and cobalt naphthenate-catalyzed oxidation of cyclohexane at 150 degrees C have been studied. 6-Hydroxyhexanoic, 6-oxohexanoic, and adipic acids are accumulated in parallel during the oxidation of cyclohexane, cyclohexanone, and 2-hydroxycyclohexanone. The critical consideration of their known formation pathways and the reactivity of possible precursors gives evidence for the predominant formation of 6-hydroxyhexanoic acid at the step of cyclohexanol oxidation and adipic acid from 2-hydroxycyclohexanol.