In this study, in situ FT-IR spectroscopy and ex situ GC and GC-MS were employed to investigate the photooxidation of cyclohexane and cyclohexene in BaY. Cyclohexane and cyclohexene were oxidized using molecular oxygen and photochemically produced tert-butyl hydroperoxide (TBHP) in BaY. The main products formed after photooxidation of cyclohexane with molecular oxygen were cyclohexanone and cyclohexanol. Cyclohexane did not react with TBHP in BaY. The main product formed after photooxidation of cyclohexene and molecular oxygen in BaY was 2-cyclohexen-1-one and the main product formed after reaction of cyclohexene with TBHP in BaY was 1,2-epoxy cyclohexane. In general, it was found that the photooxidation of cyclohexene using 02 or TBHP gave consistently higher activity but lower selectivity than that found for cyclohexane photooxidation, due to the presence of two active reaction centers (alpha-H and C=C bond) in cyclohexene. It was also shown that for cyclohexene oxidation in BaY, the choice of oxidant significantly alters the product distribution. (C) 2002 Elsevier Science B.V. All rights reserved.