Decomposition of cumene hydroperoxide (CHP) was undertaken in a free radical chain reaction. The peroxyl group is very active and unstable, while the remainder of the molecule is inert. CHP reacted with various concentrations of dilute sodium hydroxide as a catalyst to cleave at ambient and decomposition temperature. The products were verified by GC/MS, and were quantitatively analyzed by chromatography. CHP cleaved heterolytic with. NaOH at 250 degrees C, whose major product was dimethylphenyl carbinol (DMPC); however, the main products become acetophenone and (x-methylstyrene by cleaved homolytic pathway. The catalytic concentrations of NaOH significantly affected the branch ratios of DMPC under decomposition. Based on the experimental results, a radical cleavage mechanism was proposed. To sum up, the reaction parameters, such as temperature, Lewis base, etc., could affect the incompatibilities and decomposition pathways for proper CHP cleavage process. In addition, exothermic onset temperatures (T-0) and heat of decomposition (Delta H-d) of incompatible mixtures and CUP itself were studied by differential scanning calorimetry (DSC). Comparisons of T-0, Delta H-d and peak power were assessed to corroborate the severity of thermal hazards. From the decay rate of CHP concentration, the reaction order was determined to be 0.5, and the Arrhenius parameters were measured as E-a = 92.1 kJ/mol and frequency factor A = 2.42 x 10(10) min(-1). (c) 2007 Elsevier B.V. All rights reserved.