The compound, 2,5-diphenyl-3,4-di(2-pyridyl)cyclopentadienone (2), has been synthesized by thermal dehydration of 2,5-diphenyl-3,4-di(2-pyridyl)cyclopentandiolone (1) over silica gel under N-2 atmosphere at 200 degrees C. The product (2), has been characterized by elemental analysis, IR, UV-VIS, and H-1 NMR spectroscopy. Thermal dehydration of (1) over silica gel has also been studied by TGA, DTG, and DSC. The effective kinetic and thermodynamic parameters of dehydration have been estimated, and a mechanism of dehydration from Bronsted sites on silica gel has been proposed. Comparative dehydration experiments using gamma-Al2O3, ZnO, and NiSO4 proved silica gel to be superior in converting compound (1) to (2).